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Clinical Context

Pregnant women do not seem to be more susceptible to SARS-CoV-2 infection than non-pregnant women, but they are at higher risk of severe COVID-19 disease. COVID-19 is known to increase the risk for complications during pregnancy, including a 2-fold increase in the risk for admission to intensive care units and a 70% increase in the risk for maternal death compared with nonpregnant women with symptomatic COVID-19; however, the rate of COVID-19 vaccination during pregnancy remains low, in part because of concerns regarding the safety of the vaccine in pregnancy. Lipkind and colleagues investigated whether the COVID-19 vaccine might promote higher risks for preterm or small-for-gestational-age (SGA) births, and their findings were documented in the January 7 issue of Morbidity and Mortality Weekly Report.

Researchers used the US Vaccine Safety Datalink to address their study question. This database contains information on approximately 3% of the US population. Only 21.8% of women received at least 1 dose of a COVID-19 vaccine during pregnancy, with nearly all vaccinations occurring in the second and third trimesters; however, the vaccine was not associated with risk for either preterm or SGA infants at delivery, regardless of the number of vaccine doses.

Can the vaccine be protective against the incidence and complications of COVID-19 during pregnancy? The current study by Stock and colleagues addresses this issue.

Study Synopsis and Perspective

Two new studies show how COVID-19 threatens the health of pregnant people and their newborn infants.

A study conducted in Scotland showed that unvaccinated pregnant people who got COVID-19 were much more likely to have a stillborn infant or one that dies in the first 28 days. The study also found that pregnant women infected with SARS-CoV-2, the virus that causes COVID-19, died and needed hospitalization at a much higher rate than vaccinated women who got pregnant.

The University of Edinburgh and Public Health Scotland studied national data in nearly 88,000 women between December 2020 and October 2021, according to the study published in Nature Medicine.^[2]

Overall, 77.4% of SARS-CoV-2 infections, 90.9% of COVID-19--related hospitalizations, and 98% of critical care cases occurred in the unvaccinated people, as did all newborn deaths.

The study said 2364 babies were born to women infected with SARS-CoV-2, with 2353 live births; 11 babies were stillborn and 8 live-born babies died within 28 days. Of the live births, 241 were premature.

The problems were more likely if infection occurred 28 days or fewer before the delivery date, the researchers said.

The authors said the low vaccination rate among pregnant people was a problem. Only 32% of people giving birth in October 2021 were fully vaccinated whereas 77% of the Scottish female population aged 18 to 44 years were fully vaccinated.

"Vaccine hesitancy in pregnancy thus requires addressing, especially in light of new recommendations for booster vaccination administration 3 months after the initial vaccination course to help protect against new variants such as Omicron," the authors wrote. "Addressing low vaccine uptake rates in pregnant women is imperative to protect the health of women and babies in the ongoing pandemic."

Vaccinated women who were pregnant had complication rates that were about the same for all pregnant women, the study shows.

The second study, published in Lancet,^[3] found that women who got COVID-19 while pregnant in 5 Western US states were more likely to have premature births, low birth weights, and stillbirths, even when the COVID-19 cases are mild.

The Institute for Systems Biology researchers in Seattle studied data for women who gave birth in Alaska, California, Montana, Oregon, or Washington from March 5, 2020, to July 4, 2021. About 18,000 of them were tested for COVID-19, with 882 testing positive. Of the positive tests, 85 occurred in the first trimester, 226 in the second trimester, and 571 in the third semester. None of the pregnant women had been vaccinated at the time they were infected.

Most of the birth problems occurred with first- and second-trimester infections, the study noted, and problems occurred even if the pregnant person did not have respiratory complications, a major COVID-19 symptom.

“Pregnant people are at an increased risk of adverse outcomes following SARS-CoV-2 infection, even when maternal COVID-19 is less severe, and they may benefit from increased monitoring following infection,” Jennifer Hadlock, MD, an author of the paper, said in a news release.^[4]

The study also pointed out continuing inequities in health care, with most of the positive cases occurring among young, non-White people with Medicaid and high body mass indices.

Study Strengths

• The researchers used population data with high data completeness.
• The data describe changes in vaccine uptake over time, with the most contemporary data available included.

Study Limitations

• The data presented are descriptive and have not adjusted for the potential confounding influence of demographics, obstetric or medical conditions.
• The researchers were unable to differentiate between hospital and critical care admissions due to SARS-CoV-2 infection from admissions for obstetric care with coincidental SARS-CoV-2 infection.
• Due to source data latency, the most recent 3 months’ pregnancy data may be less complete. This may be a result of some under-ascertainment of the most recent pregnancies and end of pregnancy outcomes.

Clinical Implications

• A previous study by Lipkind and colleagues found that the COVID-19 vaccine during pregnancy was not significantly associated with the risks for preterm or SGA births.
• In the current study by Stock and colleagues, the COVID-19 vaccine was effective in preventing incident SARS-CoV-2 infection and severe COVID-19 among pregnant women. SARS-CoV-2 infection during pregnancy was associated with higher rates of preterm birth and death in the extended perinatal period.
• Implications for the healthcare team: Healthcare providers should be aware of vaccine hesitancy in this population and continue to provide evidence-based education on the COVID-19 vaccine during pregnancy especially for younger and more deprived populations.

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