By Letitia Stein

The U.S. Centers for Disease Control and Prevention issued guidelines on Friday recommending how long men and women exposed to the Zika virus should wait before trying to conceive babies.

Zika has been linked to a spike in microcephaly, a rare birth defect, in Brazil.

Women diagnosed with Zika should wait at least eight weeks after symptoms began before trying to conceive, while men should hold off for at least six months, health officials recommended.

Both men and women who were possibly exposed to the virus should wait for at least eight weeks before attempting conception, the guidelines said.

Health officials noted the recommendations were based on limited data about Zika's persistence in blood and semen.

Zika has not been proven to cause microcephaly in babies, but there is growing evidence that suggests a link. The condition is defined by unusually small heads that can result in developmental problems.

Brazil said it has confirmed more than 900 cases of microcephaly, and considers most of them to be related to Zika infections in the mothers. Brazil is investigating nearly 4,300 additional suspected cases of microcephaly.