NEW YORK — Federal health officials on Friday issued first-time guidance for couples planning a pregnancy if either partner may have been exposed to Zika, the tropical disease linked to birth defects.

The disease is mainly spread through mosquito bites, but authorities have come to realize that it also can be transmitted sexually. That Centers for Disease Control and Prevention had previously said that when a woman is pregnant, a couple should abstain from sex or use condoms during the entire pregnancy if the man may have been infected with Zika.

Now the CDC says a couple who are trying to conceive should use condoms every time or abstain for six months if the man had confirmed illness or Zika symptoms and was in an outbreak area.

If the male partner was in a Zika outbreak area but didn’t get sick, they should abstain or use condoms for eight weeks, the new guidance says.

If the woman has Zika or Zika symptoms, they should wait at least eight weeks after the symptoms before trying to conceive, the CDC said.

The guidelines come from taking the current understanding of how long Zika persists in blood or semen, and then tripling the time for safe measure, said the CDC’s Dr. Denise Jamieson.

Some countries where Zika has spread have suggested that all their women postpone pregnancies. El Salvador, for example, has suggested that women not become pregnant until 2018.

In another report issued Friday, CDC officials said tens of thousands of IUDs and other forms of birth control are badly needed in Puerto Rico to help prevent unintended pregnancies during an outbreak of Zika there. An estimated 138,000 young Puerto Rican women do not want to get pregnant but are not using effective birth control. Often the reason is they can’t afford it.