When a woman who wants to have a child provides her fertilized ovum to another woman who carries it through pregnancy and gives birth to a child, who is the child’s legal mother? Unlike the majority, I do not agree that the determinative consideration should be the intent to have the child that originated with the woman who contributed *103the ovum. In my view, the woman who provided the fertilized ovum and the woman who gave birth to the child both have substantial claims to legal motherhood. Pregnancy entails a unique commitment, both psychological and emotional, to an unborn child. No less substantial, however, is the contribution of the woman from whose egg the child developed and without whose desire the child would not exist.
For each child, California law accords the legal rights and responsibilities of parenthood to only one “natural mother.” When, as here, the female reproductive role is divided between two women, California law requires courts to make a decision as to which woman is the child’s natural mother, but provides no standards by which to make that decision. The majority’s resort to “intent” to break the “tie” between the genetic and gestational mothers is unsupported by statute, and, in the absence of appropriate protections in the law to guard against abuse of surrogacy arrangements, it is ill-advised. To determine who is the legal mother of a child born of a gestational surrogacy arrangement, I would apply the standard most protective of child welfare—the best interests of the child.
I. Factual Background
This case arises from an agreement made between Mark and Crispina Calvert, a married couple, and Anna Johnson, a single woman. As the result of a hysterectomy, Crispina was unable to become pregnant, although her ovaries could still produce eggs. When she and her husband Mark desired to have a child, they arranged with Anna for Anna’s impregnation with an embryo formed from Crispina’s egg and Mark’s sperm. Mark and Crispina agreed to pay Anna installment payments totaling $10,000, the last installment not due until six weeks after Anna gave birth. In exchange, Anna agreed to carry the child to term and, after giving birth, to relinquish her parental rights to the child.
Six months into the pregnancy, Anna’s relationship with Mark and Crispina broke down. Both sides filed lawsuits seeking declarations of parental rights in the unborn child. While these consolidated actions were still pending, on September 19, 1990, Anna gave birth. By agreement of the parties, the court awarded immediate custody of the child to Mark and Crispina, but granted visitation rights to Anna.
The matter went to trial in October 1990. The parties stipulated that Mark and Crispina were the genetic parents of the child to whom Anna had given birth. The trial court ruled in favor of Mark and Crispina, concluding that as the child’s “genetic” and “biological” father and mother, they were also his “natural” father and mother. The Court of Appeal affirmed.
*104We granted review to address an issue of first impression: Under California law, how does a court determine who is the legal mother of a child born of a gestational surrogacy arrangement?
II. This Opinion’s Approach
The determination of a question of parental rights to a child born of a surrogacy arrangement was before the New Jersey Supreme Court in Matter of Baby M. (1988) 109 N.J. 396 [537 A.2d 1227, 77 A.L.R.4th 1], a case that received worldwide attention. But in the surrogacy arrangement at issue there the woman who gave birth to the child, Marybeth Whitehead, had been impregnated by artificial insemination with the sperm of the intending father, William Stern. Whitehead thus provided the genetic material and carried the fetus to term. This case is different, because here those two aspects of the female role in reproduction were divided between two women. This process is known as “gestational” surrogacy, to distinguish it from the surrogacy arrangement involved in Baby M.1
In this opinion, I first discuss gestational surrogacy in light of the medical advances that have made it a reality. I next consider the wider social and philosophical implications of using gestational surrogacy to give birth to a child, and set out some of the suggested models for deciding the child’s parentage in this situation. I then review a comprehensive model legislative scheme, not enacted in California, designed to accommodate the interests of all participants in surrogacy arrangements. I next turn to California’s Uniform Parentage Act, and critique the majority’s reliance on “intent” as the determinative factor under that act in deciding who is the “natural,” and thus legal, mother of a child born of a gestational surrogacy arrangement. Finally, I explain why, in the absence of legislation designed to address the unique problems of gestational surrogacy, courts deciding who is the legal mother of a child born of gestational surrogacy should look to the best interests of that child.
*105III. Gestational Surrogacy
Recent advances in medical technology have dramatically expanded the means of human reproduction. Among the new technologies are in vitro fertilization, embryo and gamete freezing and storage, gamete intra-fallopian transfer, and embryo transplantation. (Shultz, Reproductive Technology and Intent-Based Parenthood: An Opportunity for Gender Neutrality, 1990 Wis.L.Rev. 297, 299 fn. 5 [hereafter Reproductive Technology].) Gestational surrogacy is the result of two of these techniques: in vitro fertilization and embryo transplantation. (See Shalev, Birth Power: The Case for Surrogacy (Yale U. Press 1989) p. 115.)
In vitro fertilization or IVF is the fertilization of a human egg outside the human body in a laboratory. Children that have been conceived this way are often called “test tube babies,” because their actual conception took place in a petri dish. The first live birth of a child conceived in vitro occurred in 1979 in Great Britain after 20 years of research by a British team. (Shalev, Birth Power: The Case for Surrogacy, supra, at p. 105.)
To facilitate the retrieval or “harvesting” of eggs for in vitro fertilization, a woman ingests fertility hormones to induce “superovulation” or the production of multiple eggs. The eggs are then removed through aspiration, a nonsurgical technique, or through an invasive surgical procedure known as laparoscopy. (See generally Developments in the Law: Medical Technology and the Law (1990) 103 Harv.L.Rev. 1519, 1537-1542 [hereafter Medical Technology].) To undergo superovulation and egg retrieval is taxing, both physically and emotionally; the hormones used for superovulation produce bodily changes similar to those experienced in pregnancy, while the surgical removal of mature eggs has been likened to caesarian-section childbirth. (Id., at p. 1540; Shalev, Birth Power: The Case for Surrogacy, supra, at pp. 117-118.)
After removal, eggs are exposed to live sperm in a petri dish. If an egg is fertilized, the resulting zygote is allowed to divide and become multicellular before uterine implantation. The expense and low success rate of in vitro fertilization demonstrate j'ust how much prospective parents are willing to endure to achieve biological parenthood. (Medical Technology, supra, 103 Harv.L.Rev. at p. 1539.)
Generally, an egg fertilized in vitro is implanted in the uterus of the woman who produced it. The technique, however, allows for embryo transplantation, which is the transfer of an embryo formed from one woman’s egg to the uterus of another woman who will gestate the fetus to term. This can *106take place in at least three different situations: (1) a woman may donate an egg that, when fertilized, will be implanted in the uterus of a woman who intends to raise the child; (2) the woman who provides the egg may herself intend to raise the child carried to term by a gestational surrogate; or (3) a couple desiring a child may arrange for a surrogate to gestate an embryo produced from an egg and sperm, both donated (perhaps by close relatives of the couple). (Goodwin, Determination of Legal Parentage in Egg Donation, Embryo Transplantation, and Gestational Surrogacy Arrangements (1992) 26 Fam.L.Q. 275, 276-277 [hereafter Determination of Legal Parentage].)
The division of the female reproductive role in gestational surrogacy points up the three discrete aspects of motherhood: genetic, gestational and social. The woman who contributes the egg that becomes the fetus has played the genetic role of motherhood; the gestational aspect is provided by the woman who carries the fetus to term and gives birth to the child; and the woman who ultimately raises the child and assumes the responsibilities of parenthood is the child’s social mother. (Shalev, Birth Power: The Case for Surrogacy, supra, at p. 115; see also Macklin, Artificial Means of Reproduction and Our Understanding of the Family (1991) 21 Hastings Center Rep. 5, 6.)
IV. Policy Considerations
The ethical, moral and legal implications of using gestational surrogacy for human reproduction have engendered substantial debate. A review of the scholarly literature that addresses gestational surrogacy reveals little consensus on the desirability of surrogacy arrangements, particularly those involving paid surrogacy, or on how best to decide questions of the parentage of children born of such arrangements.
Surrogacy proponents generally contend that gestational surrogacy, like the other reproductive technologies that extend the ability to procreate to persons who might not otherwise be able to have children, enhances “individual freedom, fulfillment and responsibility.” (Shultz, Reproductive Technology, supra, 1990 Wis.L.Rev. 297, 303.) Under this view, women capable of bearing children should be allowed to freely agree to be paid to do so by infertile couples desiring to form a family. (Shalev, Birth Power: The Case for Surrogacy, supra, at p. 145 [arguing for a “free market in reproduction” in which the “reproducing woman” operates as an “autonomous moral and economic agent”]; see also Posner, Economic Analysis of Law (3d ed. 1986) p. 139; Landes & Posner, The Economics of the Baby Shortage (1978) 7 J. Legal Stud. 323 [proposing a “market in babies”].) The “surrogate mother” is expected “to weigh the prospective investment in her birthing labor” *107before entering into the arrangement, and, if her “autonomous reproductive decision” is “voluntary,” she should be held responsible for it so as “to fulfill the expectations of the other parties . . . (Shalev, Birth Power: The Case for Surrogacy, supra, at p. 96.)
One constitutional law scholar argues that the use of techniques such as gestational surrogacy is constitutionally protected and should be restricted only on a showing of a compelling state interest. (Robertson, Procreative Liberty and the Control of Conception, Pregnancy, and Childbirth (1983) 69 Va.L.Rev. 405; Robertson, Procreative Liberty and the State’s Burden of Proof in Regulating Noncoital Reproduction, in Surrogate Motherhood, supra, pp. 24-26, 35; Robertson, Embryos, Families, and Procreative Liberty: The Legal Structure of the New Reproduction (1986) 59 So.Cal.L.Rev. 939, 960.) Professor Robertson reasons that procreation is itself protected under decisions of the United States Supreme Court that affirm the basic civil right to marry and raise children. (Robertson, Procreative Liberty and the Control of Conception, Pregnancy, and Childbirth, supra, 69 Va.L.Rev. at p. 414, fns. 22, 23, citing Meyer v. Nebraska (1923) 262 U.S. 390, 399 [67 L.Ed. 1042, 1045, 43 S.Ct. 625, 29 A.L.R. 1446] [“right... to marry, establish a home and bring up children” protected by the Fourteenth Amendment]; Skinner v. Oklahoma (1942) 316 U.S. 535, 541 [86 L.Ed. 1655, 1660, 62 S.Ct. 1110] [describing marriage and procreation as basic human civil rights]; Stanley v. Illinois (1972) 405 U.S. 645, 651 [31 L.Ed.2d 551, 558-559, 92 S.Ct. 1208] [emphasizing the importance of the rights “to conceive and raise one’s children”].) From this premise, he argues that the right to procreate should extend to persons who cannot conceive or bear children. (Robertson, Procreative Liberty and the Control of Conception, Pregnancy and Childbirth, supra, 69 Va.L.Rev. at p. 411 [“Sterility bars one from conceiving or bearing only to the extent that medicine or society cannot overcome the particular cause of infertility”]; Robertson, Embryos, Families, and Procreative Liberty: The Legal Structure of the New Reproduction, supra, 59 So.Cal.L.Rev. at p. 960 [“The use of noncoital techniques . . . should . . . also be protected.”].)
Professor Robertson’s thesis of broad application of the right of privacy for all procreational techniques has been questioned, however, in light of recent United States Supreme Court jurisprudence. (See Medical Technology, supra, 103 Harv.L.Rev. 1519, 1530, citing Michael H. v. Gerald D. (1989) 491 U.S. 110 [105 L.Ed.2d 91, 109 S.Ct. 2333], as evidence of the high court’s reluctance “to extend the right of privacy to new relationships and activities” that the court has not perceived to merit “traditional protection.”)
Surrogacy critics, however, maintain that the payment of money for the gestation and relinquishment of a child threatens the economic exploitation *108of poor women who may be induced to engage in commercial surrogacy arrangements out of financial need. (Capron & Radin, Choosing Family Law Over Contract Law as a Paradigm for Surrogate Motherhood, in Surrogate Motherhood, supra, p. 62.) Some fear the development of a “breeder” class of poor women who will be regularly employed to bear children for the economically advantaged. (See Women and Children Used in Systems of Surrogacy: Position Statement of the Institute on Women and Technology, in Surrogate Motherhood, supra, at p. 322; and Corea, Junk Liberty, testimony before Cal. Assem. Judiciary Com., April 5,1988, in Surrogate Motherhood, supra, at pp. 325, 335.) Others suggest that women who enter into surrogacy arrangements may underestimate the psychological impact of relinquishing a child they have nurtured in their bodies for nine months. (See Macklin, Artificial Means of Reproduction and Our Understanding of the Family, supra, 21 Hastings Center Rep. 5, 10.)
Gestational surrogacy is also said to be “dehumanizing” (Capron & Radin, Choosing Family Law Over Contract Law as a Paradigm for Surrogate Motherhood, in Surrogate Motherhood, supra, at p. 62) and to “commodify” women and children by treating the female reproductive capacity and the children born of gestational surrogacy arrangements as products that can be bought and sold (Radin, Market-Inalienability (1987) 100 Harv.L.Rev. 1849, 1930-1932). The commodification of women and children, it is feared, will reinforce oppressive gender stereotypes and threaten the well-being of all children. (Medical Technology, supra, 103 Harv.L.Rev. 1519, 1550; Annas, Fairy Tales Surrogate Mothers Tell, in Surrogate Motherhood, supra, p. 50.) Some critics foresee promotion of an ever-expanding “business of surrogacy brokerage.” (E.g., Goodwin, Determination of Legal Parentage, supra, 26 Fam.L.Q. at p. 283.)
Whether surrogacy contracts are viewed as personal service agreements or agreements for the sale of the child born as the result of the agreement, commentators critical of contractual surrogacy view these contracts as contrary to public policy and thus not enforceable. (Radin, Market-Inalienability, supra, 100 Harv.L.Rev. at p. 1924, fn. 261; Capron & Radin, Choosing Family Law Over Contract Law as a Paradigm for Surrogate Motherhood, supra, in Surrogate Motherhood, at pp. 62-63; see also Krimmel, Can Surrogate Parenting Be Stopped? An Inspection of the Constitutional and Pragmatic Aspects of Outlawing Surrogate Mother Arrangements (1992) 27 Val.U.L.Rev. 1, 4-5.)
Organizations representing diverse viewpoints share many of the concerns highlighted by the legal commentators. For example, the American Medical Association considers the conception of a child for relinquishment after birth *109to pose grave ethical problems. (Rep. of the Judicial Council, in Surrogate Motherhood, supra, at p. 304.) Likewise, the official position of the Catholic Church is that surrogacy arrangements are “ ‘contrary to the unity of marriage and to the dignity of the procreation of the human person.’ ” (Magisterium of the Catholic Church, Instruction on Respect for Human Life in Its Origin and on the Dignity of Procreation: Replies to Certain Questions of the Day 25 (Feb. 22, 1987), cited in Radin, Market-Inalienability, supra, 100 Harv.L.Rev. 1849, 1928, fn. 271.)
The policy statement of the New York State Task Force on Life and the Law sums up the broad range of ethical problems that commercial surrogacy arrangements are viewed to present: “The gestation of children as a service for others in exchange for a fee is a radical departure from the way in which society understands and values pregnancy. It substitutes commercial values for the web of social, affective and moral meanings associated with human reproduction .... This transformation has profound implications for childbearing, for women, and for the relationship between parents and the children they bring into the world. [][]... [f] Surrogate parenting allows the genetic, gestational and social components of parenthood to be fragmented, creating unprecedented relationships among people bound together by contractual obligation rather than by the bonds of kinship and caring. ... [SI] ...[][]... Surrogate parenting alters deep-rooted social and moral assumptions about the relationship between parents and children. . . . [<j[]. . . [It] is premised on the ability and willingness of women to abdicate [their parental] responsibility without moral compunction or regret [and] makes the obligations that accompany parenthood alienable and negotiable.” (New York State Task Force on Life and the Law, Surrogate Parenting: Analysis and Recommendations for Public Policy (May 1988) in Surrogate Motherhood, supra, at pp. 317-318.)
Proponents and critics of gestational surrogacy propose widely differing approaches for deciding who should be the legal mother of a child bom of a gestational surrogacy arrangement. Surrogacy advocates propose to enforce pre-conception contracts in which gestational mothers have agreed to relinquish parental rights, and, thus, would make “bargained-for intentions determinative of legal parenthood.” (Shultz, Reproductive Technology, supra, 1990 Wis.L.Rev. at p. 323.) Professor Robertson, for instance, contends that “The right to noncoital, collaborative reproduction also includes the right of the parties to agree how they should allocate their obligations and entitlements with respect to the child. Legal presumptions of paternity and maternity would be overridden by this agreement of the parties.” (Robertson, Procreative Liberty and the Control of Conception, Pregnancy, and Childbirth, supra, 69 Va.L.Rev. 405, 436; see also Shalev, Birth Power: The Case *110for Surrogacy, supra, at p. 141 [arguing for enforcing the parties’ legal expectations].)
Surrogacy critics, on the other hand, consider the unique female role in human reproduction as the determinative factor in questions of legal parentage. They reason that although males and females both contribute genetic material for the child, the act of gestating the fetus falls only on the female. (See Radin, Market-Inalienability, supra, 100 Harv.L.Rev. 1849, 1932, fn. 285 [pointing out the “asymmetrical” interests of males and females in human reproduction].) Accordingly, in their view, a woman who, as the result of gestational surrogacy, is not genetically related to the child she bears is like any other woman who gives birth to a child. In either situation the woman giving birth is the child’s mother. (See Capron & Radin, Choosing Family Law Over Contract Law as a Paradigm for Surrogate Motherhood, in Surrogate Motherhood, supra, at pp. 64-65.) Under this approach, the laws governing adoption should govern the parental rights to a child bom of gestational surrogacy. Upon the birth of the child, the gestational mother can decide whether or not to relinquish her parental rights in favor of the genetic mother. (Ibid.)
V. Model Legislation
The debate over whom the law should recognize as the legal mother of a child born of a gestational surrogacy arrangement prompted the National Conference of Commissioners on Uniform State Laws to propose the Uniform Status of Children of Assisted Conception Act. (9B West’s U. Laws Ann. (1992 Supp.) Uniform Status of Children of Assisted Conception Act (1988 Act) pp. 122-137 [hereafter also USCACA].) This model legislation addresses many of the concerns discussed above.
The commissioners gave careful consideration to the competing interests of the various participants in assisted conception arrangements, and sought to accommodate those interests in the model legislation. Their overriding concern, however, was the well-being of children born of gestational surrogacy and other types of assisted conception. As the foreword to the model legislation notes, the extraordinary circumstances of these children’s births deprive them of parentage in the traditional sense. (9B West’s U. Laws Ann. (1992 Supp.) USCACA, supra, at p. 123.) Thus, the intent of the proposed legislation was to define with precision the legal status of these children as well as to codify the rights of the other participants in a surrogacy arrangement. The commissioners proposed alternative versions of the USCACA: one that would disallow gestational surrogacy and another that would permit it only under court supervision.
*111In its key components, the proposed legislation provides that “a woman who gives birth to a child is the child’s mother” (USCACA, § 2) unless a court has approved a surrogacy agreement before conception (USCACA, § 5, 6). In the absence of such court approval, any surrogacy agreement would be void. (USCACA, § 5, subd. (b).) If, however, the arrangement for gestational surrogacy has court approval, “the intended parents are the parents of the child.” (USCACA, § 8, subd. (a)(1).)
To obtain court approval, the parties to the surrogacy arrangement must file a petition. (USCACA, § 6, subd. (a).) The model legislation provides for the court to appoint a guardian ad litem for the intended child and legal counsel for the surrogate mother. {Ibid.) Before approving a surrogacy arrangement, the trial court must conduct a hearing and enter detailed findings, including the following: medical evidence shows the intended mother’s inability to bear a child or that for her to do so poses an unreasonable risk to the unborn child or to the physical or mental health of the intended mother; all parties to the surrogacy agreement (including the surrogate’s husband if she has one) meet the standards of fitness of adoptive parents; the agreement was voluntary and all parties understand its terms; the surrogate mother has undergone at least one successful pregnancy and medical evidence shows that another pregnancy will not endanger her physical or mental health or pose an unreasonable risk to the unborn child; and all parties have received professional mental health counseling pertaining to the effect of the surrogacy arrangement. (USCACA, § 6, subd. (b).) These provisions serve to minimize the potential for overreaching and to ensure that all parties to a surrogacy arrangement understand their respective roles and obligations.
The USCACA offers predictability in delineating the parentage of children born of gestational surrogacy arrangements. Under the model legislation, if enacted, there would never be a question as to who has the legal responsibility for a child born of a gestational surrogacy arrangement: If the couple who initiated the surrogacy had complied with the provisions of the legislation, they would be the child’s legal parents. If they had not, the rights and responsibilities of parenthood would go to the woman who gave birth to the child and her spouse.
Because California Legislature has not enacted the Uniform Status of Children of Assisted Conception Act, its provisions were not followed in this case.
*112VI. The Uniform Parentage Act
The only California statute defining parental rights is the Uniform Parentage Act (hereafter also UPA). (See Civ. Code, § 7000 et seq.).2 The Legislature enacted the UPA to abolish the concept of illegitimacy and to replace it with the concept of parentage. (Adoption of Kelsey S. (1992) 1 Cal.4th 816, 828 [4 Cal.Rptr.2d 615, 823 P.2d 1216].) The UPA was never intended by the Legislature to govern the issues arising from new reproductive technologies such as gestational surrogacy. Nevertheless, the UPA is on its face broadly applicable, and it is in any event the only statutory guidance this court has in resolving this case.
The provisions of the UPA “extend[] equally to every child and to every parent, regardless of the marital status of the parents.” (§ 7002.) The parent-child relationship defined by the UPA accords a child’s parents both rights and obligations. (§ 7001.) A primary focus of the UPA is the determination of paternity and enforcement of financial responsibility. (§§ 7006 [actions to determine paternity], 7012 [specifying financial support obligations].)
When a child is bom by gestational surrogacy, as happened here, the two women who played biological roles in creating the child will both have statutory claims under the UPA to being the child’s natural mother. The UPA permits a woman to establish that she is “the natural mother” of a child by “proof of. . . having given birth to the child . . . .” (§ 7003, subd. (1).) Thus, a gestational mother qualifies as a “natural mother” under the statute. (Ibid.) Alternatively, the UPA allows a woman to prove she is a mother in the same manner as a man may prove he is a father. (§§ 7003, subd. (1), 7015 [permitting actions to establish a mother and child relationship using parts of the UPA “applicable to the father and child relationship”].) A man may demonstrate he is a child’s natural father through genetic marker evidence derived from blood testing. (§ 7004, subd. (a); Evid. Code, §§ 621, 892, 895.) Accordingly, a genetic mother may also demonstrate she is a child’s natural mother through such genetic evidence. Here, both Anna, the gestational mother, and Crispina, the genetic mother, have offered proof acceptable under the UPA to qualify as the child’s natural mother.
By its use of the phrase “the natural mother,” however, the UPA contemplates that a child will have only one natural mother. (§ 7003, subd. (1), italics added.) But the UPA provides no standards for determining who that natural mother should be when, as here, two different women can offer biological proof of being the natural mother of the same child under its *113provisions. Thus, the UPA by its terms cannot resolve the conflict in this case.
VII. Analysis of the Majority’s “Intent” Test
Faced with the failure of current statutory law to adequately address the issue of who is a child’s natural mother when two women qualify under the UPA, the majority breaks the “tie” by resort to a criterion not found in the UPA—the “intent” of the genetic mother to be the child’s mother.
This case presents a difficult issue. The majority’s resolution of that issue deserves serious consideration. Ultimately, however, I cannot agree that “intent” is the appropriate test for resolving this case.
The majority offers four arguments in support of its conclusion to rely on the intent of the genetic mother as the exclusive determinant for deciding who is the natural mother of a child born of gestational surrogacy. Careful examination, however, demonstrates that none of the arguments mandates the majority’s conclusion.
The first argument that the majority uses in support of its conclusion that the intent of the genetic mother to bear a child should be dispositive of the question of motherhood is “but-for” causation. Specifically, the majority relies on a commentator who writes that in a gestational surrogacy arrangement, “ ‘the child would not have been born but for the efforts of the intended parents.” (Maj. opn., ante, at p. 94, quoting Hill, What Does It Mean to Be a “Parent”? The Claims of Biology as the Basis for Parental Rights (1991) 66 N.Y.U. L.Rev. 353, 415, original italics omitted, italics added.)
The majority’s resort to “but-for” causation is curious. The concept of “but-for” causation is a “test used in determining tort liability . . . .” (Black’s Law Dict. (6th ed. 1990) p. 200.) In California, the test for causation is whether the conduct was a “substantial factor” in bringing about the event. (Mitchell v. Gonzales (1991) 54 Cal.3d 1041, 1049, 1054, 1056 [1 Cal.Rptr.2d 913] [disapproving “but-for” jury instruction in tort cases].) Neither test for causation assists the majority, as I shall discuss.
The proposition that a woman who gives birth to a child after carrying it for nine months is a “substantial factor” in the child’s birth cannot reasonably be debated. Nor can it reasonably be questioned that “but for” the gestational mother, there would not be a child. Thus, the majority’s reliance on principles of causation is misplaced. Neither the “but for” nor the “substantial factor” test of causation provides any basis for preferring the *114genetic mother’s intent as the determinative factor in gestational surrogacy cases: Both the genetic and the gestational mothers are indispensable to the birth of a child in a gestational surrogacy arrangement.
Behind the majority’s reliance on “but-for” causation as justification for its intent test is a second, closely related argument. The majority draws its second rationale from a student note: “ ‘The mental concept of the child is a controlling factor of its creation, and the originators of that concept merit full credit as conceivers.’ ” (Maj. opn., ante, at p. 94, quoting Note, Redefining Mother: A Legal Matrix for New Reproductive Technologies (1986) 96 Yale L.J. 187, 196.)
The “originators of the concept” rationale seems comfortingly familiar. The reason it seems familiar, however, is that it is a rationale that is frequently advanced as justifying the law’s protection of intellectual property. As stated by one author, “an idea belongs to its creator because the idea is a manifestation of the creator’s personality or self.” (Hughes, The Philosophy of Intellectual Property (1988) 77 Geo. L.J. 287, 330.) Thus, it may be argued, just as a song or invention is protected as the property of the “originator of the concept,” so too a child should be regarded as belonging to the originator of the concept of the child, the genetic mother.
The problem with this argument, of course, is that children are not property. Unlike songs or inventions, rights in children cannot be sold for consideration, or made freely available to the general public. Our most fundamental notions of personhood tell us it is inappropriate to treat children as property. Although the law may justly recognize that the originator of a concept has certain property rights in that concept, the originator of the concept of a child can have no such rights, because children cannot be owned as property. Accordingly, I cannot endorse the majority’s “originators of the concept” or intellectual property rationale for employing intent to break the “tie” between the genetic mother and the gestational mother of the child.
Next, the majority offers as its third rationale the notion that bargained-for expectations support its conclusion regarding the dispositive significance of the genetic mother’s intent. Specifically, the majority states that “ ‘intentions that are voluntarily chosen, deliberate, express and bargained-for ought presumptively to determine legal parenthood.’ ” (Maj. opn., ante, at p. 94, quoting Schultz, Reproductive Technology, supra, 1990 Wis. L.Rev. at p. 323.)
It is commonplace that, in real or personal property transactions governed by contracts, “intentions that are voluntarily chosen, deliberate, express and *115bargained-for” ought presumptively to be enforced and, when one party seeks to escape performance, the court may order specific performance. (See, e.g., § 3384 et seq.; 11 Witkin, Summary of Cal. Law (9th ed. 1990) Equity, § 21, p. 698.) But the courts will not compel performance of all contract obligations. For instance, even when a party to a contract for personal services (such as employment) has wilfully breached the contract, the courts will not order specific enforcement of an obligation to perform that personal service. (§ 3390; see 11 Witkin, Summary of Cal. Law, supra, Equity, § 59, p. 736.) The unsuitability of applying the notion that, because contract intentions are “voluntarily chosen, deliberate, express and bargained-for,” their performance ought to be compelled by the courts is even more clear when the concept of specific performance is used to determine the course of the life of a child. Just as children are not the intellectual property of their parents, neither are they the personal property of anyone, and their delivery cannot be ordered as a contract remedy on the same terms that a court would, for example, order a breaching party to deliver a truckload of nuts and bolts.
Thus, three of the majority’s four arguments in support of its exclusive reliance on the intent of the genetic mother as determinative in gestational surrogacy cases cannot withstand analysis. And, as I shall discuss shortly, the majority’s fourth rationale has merit, but does not support the majority’s conclusion. But before turning to the majority’s fourth rationale, I shall discuss two additional considerations, not noted by the majority, that in my view also weigh against utilizing the intent of the genetic mother as the sole determinant of the result in this case and others like it.
First, in making the intent of the genetic mother who wants to have a child the dispositive factor, the majority renders a certain result preordained and inflexible in every such case: as between an intending genetic mother and a gestational mother, the genetic mother will, under the majority’s analysis, always prevail. The majority recognizes no meaningful contribution by a woman who agrees to carry a fetus to term for the genetic mother beyond that of mere employment to perform a specified biological function.
The majority’s approach entirely devalues the substantial claims of motherhood by a gestational mother such as Anna. True, a woman who enters into a surrogacy arrangement intending to raise the child has by her intent manifested an assumption of parental responsibility in addition to her biological contribution of providing the genetic material. (See Adoption of Kelsey S., supra, 1 Cal.4th at pp. 838, 849.) But the gestational mother’s biological contribution of carrying a child for nine months and giving birth is likewise an assumption of parental responsibility. (See Dolgin, Just a Gene: *116Judicial Assumptions About Parenthood (1993) 40 UCLA L.Rev. 637, 659.) A pregnant woman’s commitment to the unborn child she carries is not just physical; it is psychological and emotional as well. The United States Supreme Court made a closely related point in Lehr v. Robertson (1983) 463 U.S. 248 [77 L.Ed.2d 614, 103 S.Ct. 2985], explaining that a father’s assertion of parental rights depended on his having assumed responsibility for the child after its birth, whereas a mother’s “parental relationship is clear” because she “carries and bears the child.” (Id. at p. 260, fn. 16 [77 L.Ed.2d at p. 626], quoting Caban v. Mohammed (1979) 441 U.S. 380, 397 [60 L.Ed.2d 297, 310, 99 S.Ct. 1760] (dis. opn. of Stewart, J.).)3 This court too has acknowledged that a pregnant woman and her unborn child comprise a “unique physical unit” and that the welfare of each is “intertwined and inseparable.” (Burgess v. Superior Court (1992) 2 Cal.4th 1064, 1080 [9 Cal.Rptr.2d 615, 831 P.2d 1197].) Indeed, a fetus would never develop into a living child absent its nurturing by the pregnant woman. (See Tribe, American Constitutional Law (2d ed. 1988) at p. 1357, citing Law, Rethinking Sex and the Constitution (1984) 132 U.Pa.L.Rev. 955, 1023.) A pregnant woman intending to bring a child into the world is more than a mere container or breeding animal; she is a conscious agent of creation no less than the genetic mother, and her humanity is implicated on a deep level. Her role should not be devalued.
To summarize, the woman who carried the fetus to term and brought a child into the world has, like the genetic mother, a substantial claim to be the natural mother of the child. The gestational mother has made an indispensable and unique biological contribution, and has also gone beyond biology in an intangible respect that, though difficult to label, cannot be denied. Accordingly, I cannot agree with the majority’s devaluation of the role of the gestational mother.
I find the majority’s reliance on “intent” unsatisfactory for yet another reason. By making intent determinative of parental rights to a child born of *117a gestational surrogacy arrangement, the majority would permit enforcement of a gestational surrogacy agreement without requiring any of the protections that would be afforded by the Uniform Status of Children of Assisted Conception Act. Under that act, the granting of parental rights to a couple that initiates a gestational surrogacy arrangement would be conditioned upon compliance with the legislation’s other provisions. They include court oversight of the gestational surrogacy arrangement before conception, legal counsel for the woman who agrees to gestate the child, a showing of need for the surrogacy, medical and mental health evaluations, and a requirement that all parties meet the standards of fitness of adoptive parents. (USCACA, §§ 5, 6.)
In my view, protective requirements such as those set forth in the USCACA are necessary to minimize any possibility in gestational surrogacy arrangements for overreaching or abuse by a party with economic advantage. As the New Jersey Supreme Court recognized, it will be a rare instance when a low income infertile couple can employ an upper income surrogate. (Matter of Baby M., supra, 537 A.2d 1227, 1249.) The model act’s carefully drafted provisions would assure that the surrogacy arrangement is a matter of medical necessity on the part of the intending parents, and not merely the product of a desire to avoid the inconveniences of pregnancy, together with the financial ability to do so. Also, by requiring both pre-conception psychological counseling for all parties and judicial approval, the model act would assure that parties enter into a surrogacy arrangement only if they are legally and psychologically capable of doing so and fully understand all the risks involved, and that the surrogacy arrangement would not be substantially detrimental to the interests of any individual. Moreover, by requiring judicial approval, the model act would significantly discourage the rapid expansion of commercial surrogacy brokerage and the resulting commodification of the products of pregnancy. In contrast, here the majority’s grant of parental rights to the intending mother contains no provisions for the procedural protections suggested by the commissioners who drafted the model act. The majority opinion is a sweeping endorsement of unregulated gestational surrogacy.
The majority’s final argument in support of using the intent of the genetic mother as the exclusive determinant of the outcome in gestational surrogacy cases is that preferring the intending mother serves the child’s interests, which are “ ‘[ujnlikely to run contrary to those of adults who choose to bring [the child] into being.’ ” (Maj. opn., ante, at p. 94, quoting Schultz, Reproductive Technology, supra, 1990 Wis. L.Rev. at p. 397.)
I agree with the majority that the best interests of the child is an important goal; indeed, as I shall explain, the best interests of the child, rather than the *118intent of the genetic mother, is the proper standard to apply in the absence of legislation. The problem with the majority’s rule of intent is that application of this inflexible rule will not serve the child’s best interests in every case.
I express no view on whether the best interests of the child in this case will be served by determining that the genetic mother is or is not the natural mother under California’s Uniform Parentage Act. It may be that in this case the child’s interests will be best served by recognizing Crispina as the natural mother. But this court is not just making a rule to resolve this case. Because the UPA does not adequately address the situation of gestational surrogacy, this court is of necessity making a rule that, unless new legislation is enacted, will govern all fliture cases of gestational surrogacy in California. And all future cases will not be alike. The genetic mother and her spouse may be, in most cases, considerably more affluent than the gestational mother. But “[t]he mere fact that a couple is willing to pay a good deal of money to obtain a child does not vouchsafe that they will be suitable parents . . . .” (Capron & Radin, Choosing Family Law Over Contract Law as a Paradigm for Surrogate Motherhood, in Surrogate Motherhood, supra, at pp. 65-66.) It requires little imagination to foresee cases in which the genetic mothers are, for example, unstable or substance abusers, or in which the genetic mothers’ life circumstances change dramatically during the gestational mothers’ pregnancies, while the gestational mothers, though of a less advantaged socioeconomic class, are stable, mature, capable and willing to provide a loving family environment in which the child will flourish. Under those circumstances, the majority’s rigid reliance on the intent of the genetic mother will not serve the best interests of the child.
VIII. The Best Interests of the Child
As I have discussed, in California the existing statutory law applicable to this case is the Uniform Parentage Act which was never designed to govern the new reproductive technology of gestational surrogacy. Under the UPA, both the genetic mother and the gestational mother have an equal right to be the child’s natural mother. But the UPA allows one natural mother for each child, and thus this court is required to make a choice. To break this “tie” between the genetic mother and the gestational mother, the majority uses the legal concept of intent. In so doing, the majority has articulated a rationale for using the concept of intent that is grounded in principles of tort, intellectual property and commercial contract law.
But, as I have pointed out, we are not deciding a case involving the commission of a tort, the ownership of intellectual property, or the delivery of goods under a commercial contract; we are deciding the fate of a child. In *119the absence of legislation that is designed to address the unique problems of gestational surrogacy, this court should look not to tort, property or contract law, but to family law, as the governing paradigm and source of a rule of decision.
The allocation of parental rights and responsibilities necessarily impacts the welfare of a minor child. And in issues of child welfare, the standard that courts frequently apply is the best interests of the child. (See §§ 222.20, 222.36, 224.64 [matters relating to adoption and temporary placement], 4600 [child custody], 4601 [visitation].) Indeed, it is highly significant that the UPA itself looks to a child’s best interests in deciding another question of parental rights. (§ 7017, subd. (d)(2).) This “best interests” standard serves to assure that in the judicial resolution of disputes affecting a child’s well-being, protection of the minor child is the foremost consideration. Consequently, I would apply “the best interests of the child” standard to determine who can best assume the social and legal responsibilities of motherhood for a child born of a gestational surrogacy arrangement.4
The determination of a child’s best interests does not depend on the parties’ relative economic circumstances, which in a gestational surrogacy situation will usually favor the genetic mother and her spouse. (See Matter of Baby M., supra, 537 A.2d at p. 1249.) As this court has recognized, however, superior wealth does not necessarily equate with good parenting. (See Burchard v. Garay (1986) 42 Cal.3d 531, 540 [229 Cal.Rptr. 800, 724 P.2d 486, 62 A.L.R.4th 237].)
*120Factors that are pertinent to good parenting, and thus that are in a child’s best interests, include the ability to nurture the child physically and psychologically (Cahill, The Ethics of Surrogate Motherhood: Biology, Freedom, and Moral Obligation, in Surrogate Motherhood, supra, at p. 160), and to provide ethical and intellectual guidance (see In re Marriage of Carney (1979) 24 Cal.3d 725, 739 [157 Cal.Rptr. 383, 598 P.2d 36, 3 A.L.R.4th 1028]). Also crucial to a child’s best interests is the “well recognized right” of every child ‘to stability and continuity.” (Burchard v. Garay, supra, 42 Cal.3d at p. 546 (cone. opn. of Mosk, J.).) The intent of the genetic mother to procreate a child is certainly relevant to the question of the child’s best interests; alone, however, it should not be dispositive.
Here, the child born of the gestational surrogacy arrangement between Anna Johnson and Mark and Crispina Calvert has lived continuously with Mark and Crispina since his birth in September 1990. The trial court awarded parental rights to Mark and Crispina, concluding that as a matter of law they were the child’s “genetic, biological and natural” parents.5 In reaching that conclusion, the trial court did not treat Anna’s statutory claim to be the child’s legal mother as equal to Crispina’s, nor did the trial court consider the child’s best interests in deciding between those two equal statutory claims. Accordingly, I would remand the matter to the trial court to undertake that evaluation.
Conclusion
Recent advances in medical technology have made it possible for the human female reproductive role to be divided between two women, the genetic mother and the gestational mother. Such gestational surrogacy arrangements call for sensitivity to each of the adult participants. But the paramount concern must be the well-being of the child that gestational surrogacy has made possible.
The model legislation proposed by the National Conference of Commissioners on Uniform Laws would protect such children’s well-being by precisely defining their parentage. Such precision is not possible using a “best interests of the child” standard, which requires a case-by-case evaluation after the birth of the child. But that evaluation would afford many protections similar to those set out in USCACA, such as judicial oversight, legal counsel, and an opportunity for the court to determine who best can provide for the child.
I recognize that, for couples such as Mark and Crispina, gestational surrogacy offers the only hope of raising a child who is genetically related to *121both. But the desire for a genetically related child does not diminish the substantial concerns expressed by a broad spectrum of commentators that surrogacy left unregulated poses a fundamental threat to the well-being of women and children. This threat could largely be allayed by legislation permitting gestational surrogacy, but under court supervision and with the type of procedural requirements proposed in the USCACA that serve to protect all of those affected by a gestational surrogacy arrangement, particularly the child. In my view, the Legislature should turn its attention to the complex issues posed by gestational surrogacy.
In this opinion, I do not purport to offer a perfect solution to the difficult questions posed by gestational surrogacy; perhaps there can be no perfect solution. But in the absence of legislation specifically designed to address the complex issues of gestational surrogacy and to protect against potential abuses, I cannot join the majority’s uncritical validation of gestational surrogacy.
I would reverse the judgment of the Court of Appeal, and remand the case to the trial court for a determination of disputed parentage on the basis of the best interests of the child.
The terms “surrogacy" and “surrogate” have been criticized as being inaccurate, particularly when applied to the type of arrangement involved in Baby M., in which the child a woman bears, intending to relinquish at birth, was formed from her own egg. (See Capron & Radin, Choosing Family Law Over Contract Law as a Paradigm for Surrogate Motherhood, in Surrogate Motherhood (Gostin edit. 1990) p. 72, fn. 2; Annas, Fairy Tales Surrogate Mothers Tell, in Surrogate Motherhood, supra, at p. 46 [suggesting that the phrase “surrogate mother" derives from Harlow’s monkey studies, in which the responses of newborn monkeys were tested by isolating them in cages with cloth or wire “surrogate mothers.”].)
Because “gestational surrogacy" is now widely used to describe the situation in which one woman agrees to be impregnated with an embryo formed from another woman’s fertilized egg, I use the phrase throughout this opinion and occasionally also refer to the woman who gestates the fetus as the “surrogate."
Further undesignated statutory references are to the Civil Code.
In my view, the United States Supreme Court’s decision in Lehr v. Robertson, supra, 463 U.S. 248, does not, despite the language I have just quoted, compel a conclusion that either the gestational mother or the genetic mother in a gestational surrogacy arrangement has, at the birth of the child, a fully vested and matured constitutional right to be a parent. Rather, I read the quoted language as indicating that the high court considers that a woman who conceives by traditional means and carries a fetus to term is a parent, and that a critical indicator of parenting status for a woman is gestation. Gestation is neither necessary nor sufficient to establish motherhood; it is, however, a factor the significance of which cannot be ignored, as the majority in effect does.
This reading of Lehr v. Robertson seems consistent with the plurality opinion in Michael H. v. Gerald D., supra, 491 U.S. 110, 123 [105 L.Ed.2d 91, 105-106], holding that a claim to fatherhood premised on biology plus “an established parental relationship” did not necessarily warrant constitutional protection. The court’s precedents are, however, not entirely clear as to what will establish motherhood in a gestational surrogacy case, undoubtedly because the court has never dealt with such a case.
In a footnote responding to this opinion, the majority confuses questions of custody, which I do not address, with the issue of maternal parentage, which I do address. (See maj. opn., ante, at p. 93, fn. 10.) The majority suggests that it is somehow inappropriate for a court to look to the child’s best interests when deciding a question of parentage under the UPA; this is refuted by the express terms of the UPA itself, which, as noted above, requires the court to consider the child’s best interests in deciding another question of parentage. (§ 7017, subd. (d)(2).)
The majority is also wrong when it suggests that the “best interests” approach for resolving the disputed issue of parentage, more than the majority’s “intent” approach, raises the “specter of governmental interference” in fundamentally private matters. (Maj. opn., ante, at p. 93, fn. 10.) This court’s grant of review to decide who is the natural mother of the child placed one branch of government squarely in the middle of this controversy—as did the parties’ decisions to resort to the court system in the first place. Judicial resolution of family law matters, by its nature, necessarily involves some governmental interference in what would otherwise be private concerns.
On another point, the majority writes that the gestational mother could “voluntarily contract[ ] away any rights to the child," and that this would represent a “concession” as to the child’s best interests. (Maj. opn., ante, at p. 93, fn. 10.) It is questionable whether the parentage of children is a proper subject of contract. But even assuming that a parent could contract away parental rights to a child—for instance, by selling the child into slavery—this would not logically amount to a binding “concession” that such a sale would be in the child’s best interests.
It is uncontested that Mark is the natural father of this child.