COVID-19 significantly raises risk of severe complications in pregnant women

By Hugo Francisco de SouzaReviewed by Susha Cheriyedath, M.Sc.Dec 10 2023

In a recent study published in the journal Open Forum Infectious Diseases, researchers investigated COVID-19's impact on severe maternal morbidity (SMM), potentially lethal complications that occur during the time of childbirth. They used declassified data from over 93,600 deliveries between March 2020 and July 2021 and found that risks, particularly those of adult respiratory distress syndrome and acute renal failure, were between 1.66 and 2.22 times higher in mothers with severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2) infections during pregnancy compared to those without. In tandem with previous research identifying the severe demerits of a mother's SARS‑CoV‑2 infection on her newborn, these results highlight the critical need for prompt diagnosis and adequate treatment of the condition in prospective mothers.

Study: Risk of severe maternal morbidity associated with SARS-CoV-2 infection during pregnancy. Image Credit: SUKJAI PHOTO / Shutterstock

What makes pregnancies special?

Pregnancies are the only means by which a sexually reproducing species can persist from generation to generation. In the context of human epidemiology, however, pregnancies present an immunologically extremely vulnerable period for a prospective mother. During their pregnancy, women are at a significantly heightened risk of contracting severe illnesses, many of which can result in potentially life-threatening outcomes for them and their infants.

Recent research has suggested that pregnant women experience a greater susceptibility to  SARS‑CoV‑2, the pathogen responsible for the ongoing coronavirus disease 2019 (COVID-19) pandemic. Observational evidence presents a two- to three-fold higher risk of pregnant women contracting severe SARS‑CoV‑2 infections (needing ICU admissions and ventilation) compared to their non-pregnant counterparts.

Previous studies have investigated the impacts of SARS‑CoV‑2 infections on pregnancy outcomes. However, most of these studies have focused on the pregnancy and delivery aspects, with severe maternal morbidity (SMM) remaining understudied and poorly understood. The limited knowledge on the associations between COVID-19 and SMMs involves small, non-generalizable sample cohorts and has, thus, presented confounding results. Despite lacking a universally accepted definition, SMM generally refers to health-impacting and life-threatening events that occur during hospitalization for childbirth.

Understanding the influence of COVID-19 on SMMs is imperative, both from the medical and socioeconomic lens – if left untreated, SMMs generally result in maternal or fetal mortality; even when treated, SMMs require specialized care, which significantly increases the already high financial burden associated with routine deliveries.

About the study

In the present study, researchers used a retrospective cohort methodology to understand the frequency of COVID-19-associated SMMs across the United States (US) using declassified insurance data from the OptumLabs Data Warehouse (OLDW). All deliveries between 11 March 2020 and 1 July 2021 were included in the study, provided they were enrolled in pharmacy coverage (this insurance policy has complete medical data availability) and were enrolled in a commercial insurance plan for the 294 days preceding delivery.

Data collection comprised physician, laboratory, and facility (hospital/clinic) claims records for 294 days before and 30 days after delivery. The US Centers for Disease Control and Prevention (CDC) uses 21 criteria for SMM definition, which were adopted without alteration for this study. Additionally, gestational age at delivery was estimated from ICD-10-CM code Z3A. COVID-19 diagnostic data was obtained from the facility or physician report, with non-clinically confirmed COVID-19 cases excluded from the final cohort.

Maternal demographic and socioeconomic characteristics, including age, education, race/ethnicity, region of residence, and insurance status, were used for statistical corrections. Analyses consisted of Chi-squared tests and Poisson regressions to evaluate factors associated with SARS-CoV-2 risk and direct SMM-COVID-19 associations, respectively.

Study findings

The final study dataset comprised 93,624 deliveries between March 2020 and July 2021, 4.8% of which (4,428) were found to have a report of maternal SARS‑CoV‑2 infection during the pregnancy. Of these, 27.0% (1,211) had SARS‑CoV‑2 infections during the seven days preceding delivery, 13.5% during the month preceding delivery, and the remaining earlier during the gestation period.

Statistical analyses revealed that younger mothers were more likely to contract COVID-19 during pregnancy than their older counterparts (15-24 years versus older than 24 years). Sociodemographic correlations revealed that ethnic minorities and financially underprivileged mothers were similarly at higher risk of contracting the disease than their more affluent, White neighbors.

Of the 93,624-strong dataset, 1,983 deliveries were found to meet the US CDC's definition of SMM. Of these, 631 SMMs were related to blood transfusions, either via the transfusion of contaminated blood or via the transfusion process itself (for example, host rejection of donor blood).

Alarmingly, SMM risk was severely impacted by SARS‑CoV‑2 infection, with an up to 2.2-fold increase in SMM probability for mothers with COVID-19 infections during the week preceding delivery. Sepsis and renal failure were the worst impacted, showing a 3-4-fold increase in incidence irrespective of the time of COVID-19 infection.

"The greatest burden of SARS-CoV-2 infection in terms of impact on SMM was observed among those with at least one pre-existing medical condition. Among those with a pre-existing medical condition, the risk of SMM was nearly three times higher following SARS-CoV-2  infection compared to no infection (aRR 2.97; 95% CI 2.64 to 3.29), and among those infected, SARS-CoV2 contributed to 66% of SMM cases"

Finally, study findings suggest that SARS‑CoV‑2 infection accounts for 60% of all non-Hispanic Black SMMs and 57% of all Hispanic SSMs. Researchers estimate that between 2-3% of all SMMs may have been prevented by the early detection and treatment of COVID-19 and by policy aimed at preventing the transmission of the virus to pregnant women.