How Does Zika Affect the Fetuses of Infected Pregnant Women?

Pedro Fernando da Costa Vasconcelos, MD, PhD, director of WHO Collaborating Center for Arbovirus and Research, Evandro Chagas Institute, explains how the Zika virus affects fetuses of infected pregnant women.

Interview Transcript (slightly modified for readability)

“The infection of Zika virus in pregnant women that results in severe malformation, [including] microcephaly and congenital central nervous system malformation in the fetus, results in severe diseases.

[Some] of the pregnant women and [their] fetus[es] will develop severe disease. Others [will] not. [The infection] will cause mild disease. And other [infections] will [not] cause problem[s] in the fetus. This depends [on] the timing of [the] pregnancy. For example, we have observed that if [the mother develops an] infection during the first trimester of pregnancy, [it] is more associated with severe disease and fetal death, [including] stillbirth and [miscarriage]. And the babies that survive after this infection will have more severe disease than fetuses that are infected in the second and third trimester of pregnancy

This [was] expected because it is the same for other congenital agents causing disease in pregnant women’s fetus, [including] rubella, cytomegalovirus virus, syphilis, and so on.

The first trimester is the embryogenesis period. [It] is the moment [that] the fetus [is] formed and [takes] the appearance of [a] human. [Infection with Zika before] the embryogenesis period [is complete], is as a consequence, more severe and dangerous, because the [fetus’] organs are not formed. So the destruction of part of the cells results in severe malformations and severe disease and severe sequelaes for these babies.”