Microcephaly Prevalence in Infants Born to Zika Virus-Infected Women: A Systematic Review and Meta-Analysis

Abstract

Zika virus is an emergent flavivirus transmitted by Aedes genus mosquitoes that recently reached the Americas and was soon implicated in an increase of microcephaly incidence. The objective of the present study is to systematically review the published data and perform a meta-analysis to estimate the prevalence of microcephaly in babies born to Zika virus-infected women during pregnancy. We searched PubMed and Cochrane databases, included cohort studies, and excluded case reports and case series publications. We extracted sample sizes and the number of microcephaly cases from eight studies, which permitted a calculation of prevalence rates that are pooled in a random-effects model meta-analysis. We estimated the prevalence of microcephaly of 2.3% (95% CI = 1.0-5.3%) among all pregnancies. Limitations include mixed samples of women infected at different pregnancy times, since it is known that infection at the first trimester is associated with higher risk to congenital anomalies. The estimates are deceptively low, given the devastating impact the infection causes over children and their families. We hope our study contributes to public health knowledge to fight Zika virus epidemics to protect mothers and their newborns.

Keywords: arbovirus; congenital Zika virus syndrome; emergent diseases; flavivirus; microcephaly.

Figure 1

Flowchart of studies selected for review and inclusion on meta-analysis modeling.

Figure 2

Forest plot of the prevalence of the outcomes in the meta-analysis models 1 (top), which deals with the Zika virus-associated microcephaly prevalence among all pregnancies observed by the studies, and 2 (bottom), which deals with the Zika virus-associated microcephaly prevalence among live births only for the same studies. The plot displays pooled sample size (2914 pregnancies, model 1, or 2648 live births, model 2), individual prevalence estimates by each study, pooled prevalence estimate (fixed and random effects models), corresponding 95% confidence intervals, study weighting (fixed and random effects models), and heterogeneity measures.