Among pregnant women in the United States with completed pregnancies and laboratory evidence of possible recent Zika infection, 6% of fetuses or infants had evidence of Zika-associated birth defects, according to a study published in JAMA.

Margaret A. Honein, PhD, from the CDC, and colleagues analyzed the US Zika Pregnancy Registry (USZPR) and the proportion of fetuses or infants with birth defects potentially associated with maternal Zika virus infection and evaluated whether the proportion with birth defects differs based on the presence of maternal symptoms of Zika virus infection or by trimester of possible infection. A total of 442 pregnant women (median age, 28 years; range, 15-50 years) were included in the study, which was conducted between January 15 and September 22, 2016.

To meet inclusion for the USZPR, either the mother, the placenta, or the fetus or infant must have had laboratory evidence of possible Zika virus infections. Maternal samples included urine, serum, and amniotic fluid; fetal or infant samples included urine, serum, cerebrospinal fluid, umbilical cord, or any fetal tissue; and placental samples were assessed separately.

Continue Reading

The gestational timing of Zika virus infection for symptomatic pregnant women was based on maternal report of date of symptom onset; for asymptomatic pregnant women, timing was based on the trimester of exposure (travel to an area of active Zika virus transmission or sexual exposure). Pregnant women with exposure in the periconceptional period and first trimester were classified as having first-trimester exposure; those with multiple trimesters of exposure including the periconceptional period were classified by their trimester of exposure.

Birth defects potentially associated with Zika virus infection during pregnancy included brain abnormalities with or without microcephaly, neural tube defects and other early brain malformations, eye abnormalities, and other consequences of central nervous system dysfunction including arthrogryposis, clubfoot, congenital hip dysplasia, and congenital deafness.

Among the pregnancies assessed in the study, birth defects potentially related to Zika virus were identified in 26 (6%) fetuses or infants. Birth defects were reported for 16 of 271 women (6%) pregnant asymptomatic women and 10 of 167 (6%) of symptomatic women. Infants with microcephaly (18/442) represent 4% of completed pregnancies. Birth defects were reported in 9 of 85 (11%) completed pregnancies with maternal symptoms or exposure exclusively in the first trimester (or periconceptional period), with no reports (0%) of birth defects among fetuses or infants with prenatal exposure to Zika virus infection only in the second or third trimesters.

“These findings support the importance of screening pregnant women for Zika virus expose,” said the researchers. “Also, pregnant women should avoid travel to areas with active Zika virus transmission and consistently and correctly use condoms to prevent sexual transmission throughout pregnancy if their partner has recently traveled to an area of active Zika virus transmission.” 

Related Articles


Honein MA, Dawson AL, Petersen EE, et al. Birth defects among fetuses and infants of US women with evidence of possible Zika virus infection during pregnancy. JAMA. 2016. doi:10.1001/jama.2016.19006

This article originally appeared on Clinical Advisor