Early intrauterine Zika infection linked to birth defects among infants in the US French Territories

1. A prospective cohort including pregnant women in the US French Territories with PCR-confirmed Zika virus (ZIKV) infection found a 7% overall risk of neurologic and ocular defects among subsequent offspring.

2. A higher proportion of neurologic and ocular abnormalities were noted among infants whose mothers were infected during their first trimester.

Evidence Rating Level: 2 (Good)  

Study Rundown: Zika virus (ZIKV) infection during pregnancy has been associated with congenital birth defects among affected infants. As the degree of risk associated with this infection is not well understood, this study sought to better describe outcomes in ZIKV-infected cohort of pregnant women. ZIKV confirmed participants were followed until the end of pregnancy for any signs of neurologic or ocular abnormalities associated with ZIKV. Roughly 7% of pregnancies resulted in neurologic and ocular abnormalities that could be attributed to ZIKV. Abnormalities were found at an increased rate among infants whose mothers were infected during their first trimester compared to mothers later in pregnancy.

Strengths of this analysis included the use of a large homogenous cohort, with laboratory-confirmed exposures of interest. Limitations of this analysis included the short-follow up period that was used to assess birth outcomes; future studies may benefit from longitudinal monitoring of infants with ZIKA-associated congenital birth defects to fully characterize the impact of infection.

Click to read the study, published in NEJM

Relevant Reading: Birth Defects Among Fetuses and Infants of US Women With Evidence of Possible Zika Virus Infection During Pregnancy

In-Depth [prospective cohort study]: This prospective cohort study recruited 546 pregnant women with PCR-confirmed ZIKV over an 8-month period during 2016. Of these women, 185 (33.9%) were infected during their first trimester, 249 (45.6%) were infected during their second trimester and 112 (20.5%) were infected during their third trimester. The primary endpoint of this study was the assessment of pregnancy outcomes, split into the following categories: live-born infant with birth defects, live-born infant without birth defects, miscarriage, termination of pregnancy, or stillbirth.  Infants were evaluated shortly after birth for any presence of microcephaly, neural tube defects, ocular abnormalities, or other CNS defects. Among the total cohort, 527 pregnancies (95.0%) resulted in live births and 28 (5.0%) were still-births. There were 39 fetuses and infants (7.0%; 95% confidence interval [CI], 5.0% to 9.5%) who had observed neurologic or ocular abnormalities that could be attributed to ZIKV infection; of these, 28 were live-born, 10 were miscarried or terminated for medical reasons, and 1 was still-born. Microcephaly cases were observed among 32 fetuses and infants (5.8%) in the whole cohort. Neurologic and ocular abnormalities were more often noted among infants whose mothers were infected during their first trimester as compared to mothers who were infected during their second or third trimesters (12.7% vs 3.6% vs 5.3%, respectively; p = 0.0001). A similar phenomenon was noted among infants with documented microcephaly (3.7% first trimester; 0.8% second trimester; 0.0% third trimester; p = 0.002).

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