The decision handed down Friday means both members of a couple must be listed on birth certificates, The Des Moines (Iowa) Register reported. The court also said when a married lesbian gives birth, her wife should not have to adopt the child to become a legal parent.
The court ruled 6-0 in favor of a lesbian couple in Des Moines, upholding a lower court decision.
The justices dismissed arguments Iowa has an interest in keeping complete and accurate birth records since the state does not require biological fathers to be identified when heterosexual couples use anonymous sperm donors.
"We are very happy with the result," said Heather Gartner, the biological mother of a daughter conceived with a sperm donor. "It now helps everyone else in that same position."
Gartner and her wife, Melissa, sued the state in 2011.
The state Supreme Court legalized gay marriage in Iowa in 2009.
Chuck Hurley, general counsel for Family Leader, a conservative group, has been leading an effort to change the court by campaigning against justices who supported gay marriage.
"I don't know what you can say other than it flies in the face of Biology 101," Hurley said. "It's a bizarre decision based on the bizarre philosophy."