In a cohort study, the risk of MCMs was similar on second-trimester ultrasound scans among 80 pregnant women who tested positive for SARS-CoV-2 in the first trimester (3.8%) and in 460 pregnant women who tested negative (3.5%) (Crovetto et al., 2021). In a large surveillance study that considered maternal SARS-CoV-2 infections at any time during pregnancy, 0.6% of prenatally exposed liveborns had an MCM, a low birth prevalence that likely reflects underascertainment (Woodworth et al., 2020). Although there is no prior evidence to support that coronaviruses impact fetal development, SARS-CoV-2 infections are new to humans and, therefore, lack of evidence is not evidence of safety.Įvaluation of teratogenicity is challenged by the need for a sufficient number of exposed pregnancies, attention to the timing of both infection and enrollment during pregnancy, and an appropriately selected reference group.
Other maternal infections associated with MCMs include cytomegalovirus, herpes simplex and varicella-zoster virus, toxoplasmosis gondii, and Zika virus (Centers for Disease C, Prevention, 2005 Marquez et al., 2011 Maldonado & Read, 2017 Oliveira Melo et al., 2016 Butler, 2016 Zhang et al., 2015 Stagno & Whitley, 1985). For example, vertical transmission of influenza virus is believed to be rare, but maternal influenza infection during pregnancy has been associated with an increased risk of neural tube defects in the infant, possibly related to maternal hyperthermia (Luteijn et al., 2014). Moreover, MCMs may occur even in the absence of transplacental transmission. Cases of vertical transmission of SARS-CoV-2 have been described in pregnant women with confirmed COVID-19, including after first-trimester maternal infection however, this appears to be rare (Chen et al., 2020 Breslin et al., 2020 Fan et al., 2021 Dong et al., 2020 Zeng et al., 2020 Shende et al., 2021 Valdespino-Vazquez et al., 2021). Transplacental transmission of SARS-CoV-2 and possible induction of MCMs are serious concerns for pregnant women with COVID-19. Although results are compatible with no major teratogenic effects associated with maternal SARS-CoV-2 infection, RR estimates were imprecise and larger studies are warranted.
No specific pattern of malformations was observed. The RR was 2.5 (95%CI 0.23–27) among those enrolled before prenatal screening, and 2.2 (95%CI 0.89–5.3) in the overall study population including those enrolled post-pregnancy. Restriction to participants with complete follow-up reduced the sample size to 92 exposed and 292 unexposed reference pregnancies. Of 10,235 controls with a negative test during pregnancy, 4,172 enrolled during pregnancy. Of 17,163 participants enrolled between June 2020 and July 2021, 1727 had a SARS-CoV-2 infection during the first trimester, of whom 1,675 enrolled during pregnancy. Generalized linear models were used to estimate relative risks (RR) and 95% confidence intervals (CI). Sensitivity analyses were restricted to participants who enrolled before the availability of informative prenatal screening tests and extended to those enrolled after end of pregnancy. The analysis of MCMs includes women with either a positive SARS-CoV-2 PCR test or a clinical diagnosis of COVID-19 during the first trimester (exposed group) or a negative SARS-CoV-2 test (reference) that enrolled while pregnant. Self-administered questionnaires collected data on SARS-CoV-2 infection, pregnancy outcomes (including detailed questions on MCMs), and potential confounders. Adult women were eligible to enroll if they had a SARS-CoV-2 test, regardless of the results, or clinically confirmed COVID-19 during pregnancy. The International Registry of Coronavirus Exposure in Pregnancy (IRCEP) was designed to estimate the relative risk of adverse perinatal outcomes among women with Coronavirus Disease 2019 (COVID-19) at specific times during gestation. There is limited information about the effects of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection during the first trimester of pregnancy on the risk of major congenital malformations (MCMs).
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