A woman who promised a sperm donor he would not have to pay child support cannot renege on the deal, the Pennsylvania Supreme Court ruled.

The 3-2 decision overturns lower court rulings under which Joel L. McKiernan had been paying up to $1,500 a month to support twin boys born in August 1994 to Ivonne V. Ferguson, his former girlfriend and co-worker.

"This court takes very seriously the best interests of the children of this commonwealth, and we recognize that to rule in favor of (McKiernan) in this case denies a source of support to two children who did not ask to be born into this situation," Justice Max Baer wrote in the majority opinion issued last week.

"Absent the parties' agreement, however, the twins would not have been born at all, or would have been born to a different and anonymous sperm donor, who neither party disputes would be safe from a support order," Baer wrote.

Ferguson and McKiernan met while working together at Pennsylvania Blue Shield in Harrisburg and had a sexual relationship that had waned before Ferguson persuaded him to donate sperm for her. Courts found that the two agreed McKiernan would not have to pay child support and would not have visitation rights, but Ferguson later changed her mind and sued. Ferguson's lawyer has disputed that the agreement existed in the first place, but courts have agreed with McKiernan on that issue.

Between the time of the donation and when Ferguson sought support in 1999, McKiernan moved to Pittsburgh, got married and had a child.

A county judge called Ferguson's actions despicable but said it was in the twins' best interests that McKiernan be required to support them. In addition to monthly payments, McKiernan was also ordered to come up with $66,000 in back support, although he was not required to do so until the appeal was resolved.

McKiernan noted that the Uniform Parentage Act, a model law adopted in some form by at least 19 states but not Pennsylvania, did not require anonymity in order to protect the donor from financial responsibility.

His lawyer, John W. Purcell Jr., said Wednesday an adverse decision would have jeopardized the entire system of sperm donation.

"That wouldn't just include Pennsylvania, because we found out in the course of this trial that many doctors order their sperm for their artificial inseminations out of state," he said.

Justice J. Michael Eakin, in a dissent, said a parent cannot bargain away a child's right to support and argued that the viability of sperm banks was not the issue.

"The children point and say, 'That is our father. He should support us,"' Eakin wrote. "What are we to reply? 'No! He made a contract to conceive you through a clinic, so your father need not support you.' I find this unreasonable at best."

Arthur Caplan, chairman of the Department of Medical Ethics at the University of Pennsylvania, said the decision runs counter to the pattern established by similar cases, where the interests of the progeny have generally been given great weight.

"It sounds like the Pennsylvania court is trying to push a little harder into the brave new world of sperm, egg and embryo donation as it's evolving," Caplan said.

Despite the ruling, donors should still be cautious about informal agreements that ostensibly insulate them against having to support children they help conceive, Caplan said.

He called it an area ripe for legislative action.

"The principle of trying to spell out what a contract might be, what's a legitimate contract ... is not one the state Legislature should ignore," he said. "They should think about this."

Elizabeth Hoffman, Ferguson's lawyer, did not immediately return a phone message seeking comment left at her Harrisburg office on Wednesday.