El Salvador appears to have taken the most dramatic step so far, though the recommendation this week is not official policy. In a region that is largely Roman Catholic, the request has raised concern from the church, and many Salvadorans question the rationale for upending the national birthrate in order to counter the suspected effects of a virus.

Civil groups have also questioned the practicality of the recommendation, noting that in El Salvador pregnancies are often unplanned. Others say it is a testament to the lack of a coherent strategy from the government, and point to the difficulty of combating something as prevalent and evasive as the mosquito.

Salvadoran officials defended the measure in an interview.

“If we don’t make any recommendations to the population, we could have a high incidence of microcephaly,” said Eduardo Antonio Espinoza Fiallos, the vice minister of health. “Of those children, 99 percent will survive, but with limitations in their mental faculties.”

For most people, the effects of the Zika virus are mild. Symptoms are flulike and can last up to a week, with victims sometimes unaware that they have contracted the virus. Zika has no known cure.