OPINION OF THE COURT
Memorandum.
The order of the Appellate Division should be affirmed, without costs.
In 2000, Dawn Ward, an unmarried registered nurse, contacted Downey Side Families for Youth with hopes of adopting a special needs child. She was presented with Jeffrey, born prematurely at 27 weeks. Although Jeffrey tested positive for cocaine and syphilis at birth, Ms. Ward was informed that his mother had not habitually used drugs and alcohol during her pregnancy, and that Jeffrey was a “quiet, gentle and pleasant child.”
Jeffrey was placed with Ms. Ward on May 3, 2001, and she subsequently began receiving a $1,000 monthly subsidy to assist with his support {see NJ Admin Code § 10:121-1.3 [“Payments for the care and maintenance of a special needs child (adoption subsidy)”]). At the time of placement, he was three years old, weighed 25 pounds, drank from a bottle, was nonverbal, and *1009had been diagnosed with mild cerebral palsy and asthma. Ms. Ward enrolled Jeffrey in an early intervention program and he underwent surgeries to improve his swallowing and breathing capabilities. He began to put on weight and develop his verbal skills. On June 20, 2002, the adoption was finalized.
His emotional and mental development, however, continued to be delayed. In 2001 and 2002, Jeffrey exhibited increasingly aggressive behavior. He began eating sand and grass, biting, licking and spitting at adults, and exhibiting bouts of uncontrolled yelling. By October 2002, Jeffrey’s behavior had deteriorated even further. He regressed in toileting, dressing and eating. His behavior at daycare now included head-banging, hitting and kicking other children and throwing chairs and objects. In February 2003, he was diagnosed with pervasive developmental disorder. Jeffrey’s play therapist advised Ms. Ward that Jeffrey had significant neurological issues resulting from exposure to drugs and alcohol in utero. Another psychiatrist diagnosed him with attachment disorder, obsessive-compulsive disorder and autism.
Jeffrey’s behavior did not improve. He injured both himself and Ms. Ward during the summer of 2003, and had frequent bouts of uncontrollable behavior. In August 2003, Jeffrey was admitted to Heely House at Parsons, a private residential treatment facility, for psychological evaluations. The results were inconclusive. Ms. Ward was advised that Jeffrey would be discharged on September 2, 2003.
On September 2, 2003, Ms. Ward went to the Greene County Department of Social Services (GCDSS) and asked for a temporary relinquishment of parental rights. When GCDSS refused to accept a temporary relinquishment, Ms. Ward decided that returning Jeffrey to her home would pose too great a risk to his and her safety, and permanently surrendered her parental rights before a Greene County Family Court judge. She subsequently relinquished the monthly subsidy she had been receiving from the State of New Jersey.
In June 2004, she received a petition seeking child support for Jeffrey. A Greene County support magistrate found Ms. Ward liable for child support as the adoptive parent of Jeffrey from the date of surrender, September 2, 2003. Family Court, affirming the findings of fact and final order of support, charged Ms. Ward with “$133.54 weekly child support for Jeffrey commencing February 4, 2005 and $10,015.50 arrears from September 2, 2003 through January 28, 2005 to be paid in $10 weekly increments.” The Appellate Division affirmed.
*1010Ms. Ward contends that she should be exempt from the child support obligation as the single “parent” of a “child born out of wedlock” and that in the alternative GCDSS should be equitably estopped from enforcing the support order. We disagree.
An adoptive parent assumes all of the liabilities of a biological parent (see Betz v Horr, 276 NY 83, 89 [1937]). Upon voluntary surrender, a parent retains the obligation to provide financial support for a child until he or she is adopted or turns 21 (see Family Ct Act § 413). Although the Social Services Law carves out a limited exception from this support requirement for children born out of wedlock to unwed mothers (see Social Services Law § 398 [6] [f]; 18 NYCRR 422.4), this exception does not apply to Ms. Ward. As Jeffrey was not “begotten and born” to her, she does not qualify as the “mother of a child born” out of lawful matrimony (see Family Ct Act § 512). Like the Appellate Division, we acknowledge the apparent harsh result in this highly unusual case, but cannot conclude that the doctrine of estoppel is applicable against the State.