State and national legal groups are trying to sway the Florida Supreme Court in a parental-rights case that pits two lesbian partners who used in vitro fertilization to have a child but later ended their relationship.

The Brevard County case is unprecedented in Florida because the fertilized egg of one woman was implanted in her then-partner, who gave birth. The couple began raising the child together, but a legal battle began after a breakup that included the birth mother moving to Australia with the child.

The Fifth District Court of Appeal in December ruled the woman who provided the egg should have parental rights, which led to the case going to the Supreme Court. During the past two weeks, groups such as the American Civil Liberties Union, Lambda Legal and a coalition of law school clinics and centers at four Florida universities have urged the Supreme Court to uphold the appeals court ruling.

Briefs filed in the case raise constitutional questions and grapple with a state law aimed largely at the waiver of parental rights by egg or sperm donors. A group of attorneys that specializes in such issues said there is an increased use of reproductive procedures by same-sex couples, unmarried heterosexual couples and single people.

“As a result, state courts across the country increasingly are being called upon to decide the legal parentage of children born through assisted reproduction under circumstances not specifically addressed by legislation — as this court must do in this case,” the American Academy of Assisted Reproductive Technology Attorneys said in a brief.

The ACLU and Lambda Legal, a prominent group that works on gay and lesbian civil-rights issues, argued in a brief in a case known by the women’s initials, D.M.T. v. T.M.H. , that the Supreme Court should protect the psychological relationship between the child and the woman who provided the egg. Beyond that, the groups contend that state laws dealing with egg or sperm donations violate the equal-protection rights of lesbian couples in committed relationships.

“Florida’s donor insemination statutes discriminate based on sex and sexual orientation by treating women who provide genetic material to their female partners for purpose of creating a child they intend to raise together differently from men who provide genetic material to their female partners for the same purpose,” Cristina Alonso, a shareholder at Carlton Fields in Miami, wrote for the academy.

Legislative Action

But attorneys for the birth mother said in an April brief that nothing in state law allows the designation of two same-sex people as birth parents. The document said the Fifth DCA “created a unique and unsupportable legal fiction that a child may have two mothers.”

“Florida law has long disfavored providing certain rights based on same-sex relationships,” the brief said. “There is no recognition of same-sex marriage or rights, constitutionally or statutorily.”

It is unclear when the Supreme Court might take up the case. Documents do not identify the two women or the child, who is now eight years old.

The documents, however, provide an outline of the relationship, which lasted from 1995 until 2006. The birth mother was infertile, so the couple decided to implant a fertilized egg from the other woman.

The women separated in 2006 when the child was 2 and contact ended in December 2007 when the birth mother moved, according to a brief filed by attorneys for the other woman. The birth mother was ultimately located in Queensland, Australia.

A brief filed last month by attorneys for the woman seeking parental rights said she always intended to help raise the child and that the state law dealing with egg or sperm donors should not apply to the case. The brief refers to the woman who provided the egg as the “biological” mother.

“The biological mother did not intend to give her ova away but instead intended to be, and was, a mother to the child born from her ova for several years,” the brief said.

The woman who provided the egg has received support in briefs from the ACLU, Lambda Legal, the American Academy of Assisted Reproductive Technology Attorneys, the National Association of Social Workers and law school clinics or centers that focus on children’s issues at the University of Florida, the University of Miami, Nova Southeastern University and Barry University.

But attorneys for the birth mother said in a brief that granting parental rights to the woman who provided the egg would require action by the Legislature.

“Mere genetic participation is not sufficient to create a right to contact and parenting,” the brief said.