COVID-19 seroprevalence in a group of pregnant women compared to a group of non-pregnant women

ABSTRACT

INTRODUCTION Pregnant women are an interesting population to study in the context of the current Coronavirus Disease 2019 (COVID-19);studies are still controversial in concluding if pregnancy is a protective condition or a risk factor for a more severe form of the illness particularly when the cardiorespiratory system is affected [1,2]. Some theories support the hypothesis that, since COVID-19 is an immune condition marked by reduced lymphocytes and elevated selected proinflammatory cytokines, and similar immune expression has been demonstrated in pregnancy, pregnant women might be on higher risk for a severe form of the illness [3]. Pregnancy itself can be considered an immunological paradox the woman must develop an immunological tolerance towards a semi-allogenic fetus, which has exposed pregnant women in history to an increased risk of infection, especially viral with maternal and neonatal unfavourable outcomes [4,5]. According to other authors, immunomodulatory mechanisms employed by the pregnant status may mitigate violent immune response, may soften cytokine storm, tightly associated with severely ill COVID-19 patients, and potentially reduce SARS-CoV-2 transmission [6]. We estimated the rate of positive serology for SARS-CoV-2 in a population of healthy pregnant women, compared to a population of non-pregnant women of the same age and geographic area. We also made a comparison between the two groups in terms of previous symptoms and lifestyle. METHODS This is a transversal study including 344 pregnant women, above 18 weeks of gestation, aged between 18 and 40, attending the obstetrical clinic of the 'Maggiore della Carità' Hospital-Novara. The control group consisted of 588 non-pregnant women from the same area and the same age group. Women consented to participate in the study after being informed on the nature of the research and data managing and processing;an informed consent was therefore signed. Recruitment period was from 27th April 2020 to 1st July 2020. RESULTS A total of 344 pregnant women and 588 non-pregnant women were recruited. The rate of positive serology for SARS-CoV-2 was significantly lower in the pregnant group 9/ 344 (2.6%) vs 75/588 (12.8%) in the non-pregnant group (p < .0001). The two groups were similar in terms of occupation and in the self-reported habit to leave the house during the lockdown. Furthermore, our study does not demonstrate important differences between pregnant and non-pregnant in symptomatology except that pregnant women mostly have fever and cough while symptoms for non-pregnant women were more varied. CONCLUSIONS Pregnant women are less infected than the equivalent female population. This could be either a better immunological response or due to a more prudential lifestyle. Pregnant women might have adopted a more prudential lifestyle, due to their special condition, which may have lead them to behave with more caution, concerning the responsibility of wearing all the disposable personal protective equipment, and keeping the recommended 6 feet distance from other people.