Few women have competed in the Olympics while pregnant, but the suspicion that the Zika virus in mothers is causing birth defects is central to calculations by athletes and others planning travel to Brazil in August for the summer games.
Chief among their concerns is whether Zika, unlike similar mosquito-borne viruses, can be transmitted sexually, or remain latent in the body - possibly presenting a risk for women who become pregnant after the Olympics have ended.
More than a dozen disease experts, in interviews with Reuters, said there is no evidence at this point of long-term risk for future pregnancies. But, given the surprises seen with the virus so far, they said people should remain cautious until studies give scientists a better picture of how the virus works. They said it would take months or even years of study for definitive answers to questions about Zika's risks.
Public health agencies have urged pregnant women to avoid travel to Zika outbreak areas but have given little guidance for couples planning to start a family.
Dr. Claire Panosian, of the University of California, Los Angeles, division of infectious diseases, said that for years she has advised couples to wait several months after traveling to exotic locales before trying to conceive because of the risk of birth defects from diseases like toxoplasmosis.
Zika should be no different, she said: "Women of child-bearing age should be very scrupulous - wait several months."
The virus, which is spreading rapidly through the Americas, has been linked to a spike in microcephaly, a rare birth defect, in Brazil. The condition is defined by unusually small heads in newborns and can cause brain damage.
Zika has not been proven to cause microcephaly, but evidence of an association led the World Health Organization to declare the outbreak a global health emergency.
The U.S. Centers for Disease Control and Prevention says pregnant women should consider skipping the 2016 Olympics because of the risk of Zika infection. For women who are considering becoming pregnant - and their male partners - the agency recommends consulting their physicians in deciding whether to go to the Games.
The U.S. Food and Drug Administration, however, has suggested a more detailed time frame. It called this week for a six-month delay in all human cell or tissue donations, including of semen and eggs, from people who have had Zika infections or traveled to an outbreak area.
Canada's national health agency on Wednesday advised women who want to get pregnant to wait at least two months after traveling to countries affected by the Zika outbreak.
Eighteen women have competed in modern Olympics while pregnant according to a group of Olympic historians who publish their statistics at Sports-Reference.com. The number includes U.S. beach volleyball gold medalist Kerri Walsh, who was not yet aware she was pregnant when competing in London in 2012.
Some current Olympic hopefuls say they might think twice about the Rio Games if Zika could threaten future pregnancies, and they are hoping for some better answers before the competition begins.
"If things stood as they are right now, I probably would not go," renowned U.S. soccer goalkeeper Hope Solo told CBS last week. "At some point I do want to start a family, and I don't want to be worried."
Solo has spoken out about feeling conflicted over her two great ambitions – winning Olympic gold and becoming a mother in the future. "It's scary, and I have a lot of reservations about going to the Olympics," she said.
DeeDee Trotter, a 33-year-old Olympic sprinter and medalist who aims to make the U.S. team again this year, said in an interview she wasn't worried "if the only danger is to women who are pregnant."
That sentiment could change if a prior Zika infection is shown to pose a risk later "when I do decide to have children," she said.
The U.S. Olympic Committee has told athletes that babies may be at risk if the mother is infected with Zika while pregnant, or if she becomes pregnant within an unknown time frame after being infected.
"We have worked to ensure that all potential Olympic and Paralympic athletes are aware of the CDC's recommendations, and we will continue to do so," USOC spokesman Mark Jones said in an emailed statement. "They are the experts."