Zika in pregnant women, follow-up on nearly 1,000 pregnancies in Brazil

Abortion rate is much higher than microcephaly rate in zika virus infections occurring in the first trimester of pregnancy

Danillo L. Espósito1, Adriana A. Ferreira1, Flávia M. Moraes1, Michelli R. Persona1, Beatriz dos Ribeiro1, Suzi V. Fábio2, Luzia Márcia R. Passos2, Ana Alice M. Castro e Silva2, Benedito A. Fonseca1
1School of Medicine of Ribeirão Preto, Ribeirão Preto, S.P., Brazil, 2Ribeirão Preto Health Department, Ribeirão Preto, S.P., Brazil
B.A.L.D. Fonseca: None.
Zika virus (ZIKV) infections in pregnant women have been associated to an increased number of severe malformations, such as, microcephaly and arthrogryposis. Much of this knowledge has been acquired through clinical studies but very few prospective studies have been done in cohorts of pregnant women, and this type of study is crucial to define ZIKV infections as the cause of congenital disease. In our prospective study, a cohort of pregnant women admitted to the study, independently of their stage of pregnancy, was followed up to the end of pregnancy. The primary goal of the study was to detect infections in these women and to compare the pregnancy outcomes of women infected or not with ZIKV. Pregnant women presenting with a zika-like disease, with duration of less than four days, were evaluated and followed by an ObGyn physician and zika diagnosis was performed by RT-PCR. STORCH syndrome was investigated in every case. From February 2016 to March 2017, 1,125 pregnant women were admitted to the study and 268 became sick during the follow-up (70, 102 and 96 on the first, second and third trimester, respectively). According to these trimesters, ZIKV-infections were detected in 42, 74, and 62 pregnant women and it was evident that the zika-related complications were only observed when infection occurred in the first and second trimester. Adverse pregnancy outcomes of ZIKV-positive mothers included 4 microcephaly, two newborns with normal cephalic perimeter but with cerebral calcifications, one arthrogryposis, and most important, 9 abortions, while outcomes of ZIKV-negative mothers included two microcephaly and two abortions. The newborn with arthrogryposis died a few hours after birth. One of the abortion cases associated to ZIKV-negative patients was from a 42-year-old patient and the other was from a patient infected with dengue-1 virus. Although the number of symptomatic pregnant women was not very large, it was clear that ZIKV infections were associated to a higher number of microcephaly and, most important, to a much higher rate of abortion, especially when the infection occurred in the first trimester of the pregnancy.