Maternal Risk Factors
Pregnant women are usually considered a high-risk group for viral infections, such as SARS-CoV-2. The pregnancy induces physiological immunosuppression in women, making the mother more vulnerable to severe infections. The anatomical changes in mothers such as an increase in the transverse diameter of the thoracic cage and an elevated level of the diaphragm decreases maternal tolerance to hypoxia. The changes in lung volume and physiological vasodilation can lead to mucosal edema and increased secretions in the upper respiratory tract. In addition, alterations in cell-mediated immunity contribute to the increased susceptibility of pregnant women to be infected by intracellular respiratory pathogens like COVID-19 and cause severe pneumonia14, 18-20.
This immunosuppressive alteration in pregnancy may result due to the attenuation in cell-mediated immunity by Th1 cells due to the physiological shift to a Th2 dominant environment, which contributes to overall infectious morbidity by increasing maternal susceptibility to intracellular pathogens like viruses. However Dashraath et al postulated that changes in the hormonal levels during pregnancy which influence immunological activity against viral pathogens, in addition to physiological shift to a predominant Th2 response, may favor the expression of anti-inflammatory cytokines (IL-4 and IL-10) and other unknown immune adaptations which may serve as the predominant immune response to SARS-CoV-2, thereby resulting in a lesser severity of COVID- 19 infection as compared to the non-pregnant cohort.21-23.
Changes in the cardiovascular and respiratory systems, including increased heart rate, stroke volume, oxygen consumption, and decreased lung capacity, as well as the development of immunologic adaptations that allow a mother to tolerate an antigenically distinctive fetus, increases the risk for pregnant women to develop severe respiratory disease. It is significant that these co-morbid maternal conditions, which included preeclampsia, pregnancy-induced hypertension, uterine scarring, gestational diabetes, and uterine atony, does not appear to be significant risk factors for intrauterine transmission of SARS-CoV-2 to the fetus 17.