Impact of variants of SARS-CoV-2 on obstetrical and neonatal outcomes.

Background: SARS-CoV-2 can lead to several types of complications during pregnancy. Variant surges are associated with different severities of disease. Few studies have compared the clinical consequences of specific variants on obstetrical and neonatal outcomes. Our goal was to evaluate and compare disease severity in pregnant women and obstetrical or neonatal complications between variants of SARS-CoV-2 that have circulated in France over a two-year period (2020-2022).

Method: This retrospective cohort study included all pregnant women with a confirmed SARS-CoV-2 infection (positive naso-pharyngeal RT-PCR test) from March 12, 2020 to January 31, 2022, in three tertiary maternal referral obstetric units in the Paris metropolitan area, France. We collected clinical and laboratory data for mothers and newborns from patients' medical records. Variant identification was either available following sequencing or extrapolated from epidemiological data.

Results: There were 234/501 (47%) Wild Type (WT), 127/501 (25%) Alpha, 98/501 (20%) Delta, and 42/501 (8%) Omicron. No significative difference was found regarding two composite adverse outcomes. There were significantly more hospitalizations for severe pneumopathy in Delta variant than WT, Alpha and Omicron respectively (63% vs 26%, 35% and 6%, p<0.001), more frequent oxygen administration (23% vs 12%, 10% and 5%, p = 0,001) and more symptomatic patients at the time of testing with Delta and WT (75% and 71%) versus Alpha and Omicron variants (55% and 66% respectively, p<0.01). Stillbirth tended to be associated with variants (p = 0.06): WT 1/231 (<1%) vs 4/126 (3%), 3/94 (3%), and 1/35 (3%) in Alpha, Delta and Omicron cases respectively. No other difference was found.

Conclusion: Although the Delta variant was associated with more severe disease in pregnant women, we found no difference regarding neonatal and obstetrical outcomes. Neonatal and obstetrical specific severity may be due to mechanisms other than maternal ventilatory and general infection.