Can immunity during pregnancy influence SARS-CoV-2 infection? – A systematic review

BACKGROUND: During pregnancy, the maternal immune system must create and sustain tolerance to the allogeneic fetus while maintaining the ability to protect against microbial assaults. OBJECTIVES: Ascertain the immunological differences in immune cells of pregnant women that may influence SARS-CoV-2 infection. STUDY DESIGN: Systematic review conducted in accordance with PRISMA guidelines and registered within PROSPERO CRD42020189735. A systematic search was undertaken across ISI, PubMed, Scopus, Embase, Cochrane Library and clinical trials.gov from January 2019 up until June 2020. Eligibility criteria included COVID-19 infection, pregnancy, and availability of immune characteristics for the pregnant women. Two authors independently screened for the suitability of inclusion. MAIN OUTCOME MEASURES: Information was manually extracted from full-text articles and efforts were made to identify overlapping data. Variables extracted and analysed included the quantification of white blood cells (WBC), lymphocytes, and C-reactive protein (CRP). RESULTS: The literature search yielded 162 studies, of which 11 were considered appropriate for selection. Only four were used in this systematic review. Our research showed that pregnant women with COVID-19 only differ from other pregnant women in their lower WBC count. The proportion of reduced lymphocyte cases is similar in both groups, as is the case of C-reactive protein levels. CONCLUSIONS: In line with previous coronavirus infections, severe maternal morbidity and perinatal death with COVID-19 infection were more likely to be expected in pregnancy. Our research showed that pregnant women with COVID-19 in terms of immunity only differ from other pregnant women in their lower WBC count.