Association of ABO and Rh blood groups with obstetric outcomes in SARS-CoV-2 infected pregnancies: A prospective study with a multivariate analysis

Objective: To evaluate the influence of ABO and Rh blood groups on morbidity among SARS-CoV-2 infected pregnancies.

Design: Prospective observational study.

Setting: 78 centers of the Spanish Obstetric Emergency Group.

Population: Pregnant women with SARS-CoV-2 tested with polymerase-chain-reaction between 26-February and 5-November 2020. A cohort of 1278 SARS-CoV-2(+) pregnant women was analyzed and a concurrent comparison group of 1453 SARS-COV-2(-) patients was established.

Methods: Data were collected from medical charts. SARS-COV-2(+) was compared with SARS-COV-2(-) for differences in distribution of blood groups. We performed multivariate analysis, controlling for maternal age and ethnicity, to evaluate association of ABO and Rh blood groups with maternal and perinatal outcomes in SARS-CoV-2(+) patients with adjusted odds ratios (aOR) and 95% confidence intervals (CI).

Main outcomes measures: Medical morbidity: Symptomatic COVID-19 and medical complications. Obstetric outcomes: caesarean delivery, preterm deliveries, preterm premature rupture of membranes (PPROM), hemorrhagic events, pre-eclampsia, maternal and neonatal mortality, stillbirth.

Results: Differences were noted between blood types and Rh for age and ethnicity comparing SARS-CoV-2(+) and SARS-CoV-2(-) groups (p < 0.05). Among the SARS-CoV-2(+) cohort, the odds of symptomatic COVID-19 and obstetric hemorrhagic event were higher in Rh+ vs Rh- mothers (aOR 1.48, 95% CI 1.02-2.14, p = 0.037, and aOR 8.72, 95% CI 1.20-63.57, p = 0.033, respectively), and PPROM were higher among blood type A vs non-A mothers (aOR 2.06, 95% CI 1.01-4.18, p = 0.046).

Conclusions: In SARS-CoV-2(+) pregnant women, Rh- status was associated with a lower risk of symptomatic COVID-19, while Rh+ and blood group A were associated with obstetric hemorrhage and PPROM, respectively.