A woman who agreed to have a child with her lesbian partner, but split up with the mother before the baby's birth, cannot be forced to pay child support, the state's highest court ruled Wednesday.

The split ruling by the Supreme Judicial Court — which legalized gay marriage in a landmark ruling last year — comes in the case of a Hampshire County lesbian couple, identified in court documents as "T.F." and "B.L.," who lived together from 1996 to 2000.

B.L. at first resisted T.F.'s wishes to have a child, but later changed her mind.

The couple broke up after T.F. got pregnant by artificial insemination. After the baby was born, T.F. sued her former partner for child support. A Probate and Family Court judge turned to the state Appeals Court, which in turned passed the case the case up to the Supreme Judicial Court.

Associate Justice Judith A. Cowin wrote that the informal agreement between the two women to have a child together did not constitute an enforceable contract, and B.L. can't be forced to pay child support.

Three justices — including Chief Justice Margaret Marshall (search), who wrote the ruling legalizing same-sex marriage (search ) in Massachusetts — disagreed with the majority conclusion, saying that the implied contract between the woman is enforceable.

"The child may have been abandoned by the defendant, but he should not be abandoned by the court," Justice John M. Greaney (search ) wrote in the dissent.