Abstract
Evidence for the real impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection on preterm birth is unclear, as available series report composite pregnancy outcomes and/or do not stratify patients according to disease severity. The purpose of the research was to determine the real impact of asymptomatic/mild SARS-CoV-2 infection on preterm birth not due to maternal respiratory failure. This case-control study involved women admitted to Sant Anna Hospital, Turin, for delivery between 20 September 2020 and 9 January 2021. The cumulative incidence of Coronavirus disease-19 was compared between preterm birth (case group, n = 102) and full-term delivery (control group, n = 127). Only women with spontaneous or medically-indicated preterm birth because of placental vascular malperfusion (pregnancy-related hypertension and its complications) were included. Current or past SARS-CoV-2 infection was determined by nasopharyngeal swab testing and detection of IgM/IgG antibodies in blood samples. A significant difference in the cumulative incidence of Coronavirus disease-19 between the case (21/102, 20.5%) and the control group (32/127, 25.1%) (P= 0.50) was not observed, although the case group was burdened by a higher prevalence of three known risk factors (body mass index > 24.9, asthma, chronic hypertension) for severe Coronavirus disease-19. Logistic regression analysis showed that asymptomatic/mild SARS-CoV-2 infection was not an independent predictor of spontaneous and medically-indicated preterm birth due to pregnancy-related hypertension and its complications (0.77; 95% confidence interval, 0.41-1.43). Pregnant patients without comorbidities need to be reassured that asymptomatic/mild SARS-CoV-2 infection does not increase the risk of preterm delivery. Preterm birth and severe Coronavirus disease-19 share common risk factors (i.e., body mass index > 24.9, asthma, chronic hypertension), which may explain the high rate of indicated preterm birth due to maternal conditions reported in the literature.
Highlights
In December 2019, a novel coronavirus, termed Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), was identified in Wuhan, China
We found that the preterm birth group was burdened by a higher prevalence of three known risk factors (i.e. body mass index (BMI) > 24.9, asthma, chronic hypertension) for severe COVID-19 [26], which are risk factors for preterm birth [27]
Data analysis of risk factors known to be related to severe COVID-19, in preterm and full term pregnant women, suggests that severe COVID-19 and preterm birth share some common risk factors
Summary
In December 2019, a novel coronavirus, termed Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), was identified in Wuhan, China. The clinical presentation of infection with SARS-CoV-2 was referred to as Coronavirus disease 19 (COVID-19) and officially declared a pandemic by the World Health Organization on 11 March 2020 [1]. The WHO identified pregnant women as a vulnerable group based on preliminary reports of increased risk of stillbirth, preterm birth, and fetal growth restriction (FGR) and from accumulated knowledge of previous respiratory virus outbreaks, including the Severe acute respiratory syndrome coronavirus (SARS-CoV) and the Middle East respiratory syndrome (MERS) [2]. SARS-CoV-2 infection during pregnancy is usually asymptomatic or mild [3,4,5,6] but can lead to serious illness in a small proportion of pregnant women. COVID-19 in pregnant women has been associated with poor perinatal outcomes [9], including preterm birth and preeclampsia and low birth weight [10, 11]
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