1874. Comparison of the Risk of Birth Defects in Live Births From Pregnant Women Infected and Not Infected by Zika Virus in Guadeloupe, 2016–2017

Abstract Background In the French Territories in the Americas (FTA), the risk of birth defects possibly associated with Zika virus (ZIKV) infection was estimated at 7% among fetuses/infants in a cohort of 546 women who developed a symptomatic RT-PCR confirmed ZIKV infection during pregnancy (NEJM 2018;378:985–94). There was no concomitant prospective cohort of pregnant women without ZIKV infection to use as a control group. Methods In Guadeloupe, one of the 3 FTAs that participated in the FTA cohort study, pregnant women were recruited at the time of delivery and tested for ZIKV infection. Women who had a confirmed negative IgG serology test for ZIKV at delivery and no other positive ZIKV test during pregnancy were considered to be ZIKV noninfected. Information on the course of the pregnancy was collected retrospectively and outcomes of live born infants of ZIKV noninfected women were analyzed, using the same definition criteria as those used for the FTA cohort study. Pregnancy outcomes were compared with those of the 241 ZIKV-exposed live born infants in Guadeloupe, extracted from the FTA cohort. Results Of the 490 live born infants without in-utero exposure to ZIKV, 42 infants (8.6%) had neurological abnormalities that were described as “potentially linked to ZIKV infection”; all but one of these were microcephaly without any other brain or clinical abnormalities. The proportion of such abnormalities was not statistically different from that observed in the 241 live born infants with ZIKV exposure (6.6%, P = 0.36). When re-considering the combined 8 fetuses and 241 infants of women with confirmed ZIKV infection in Guadeloupe from the FTA cohort, only two (0.8%) live born infants and three (1.2%) medically aborted fetuses had birth defects that could still be linked to ZIKV infection. Conclusion Isolated anthropometric and other mild neurological abnormalities had the same prevalence among live born infants with and without in utero ZIKV exposure. The high prevalence of isolated microcephaly among ZIKV noninfected women in our study population suggests that the sensitive definition for microcephaly, using a −2 SD cut-off with international growth curves, may lead to an overestimate of the rate of neurological complications of ZIKV infection during pregnancy. Disclosures All Authors: No reported Disclosures.