April 05, 2022
4 min read
Source/Disclosures
Disclosures:
Magnus and Fell report no relevant financial disclosures. Please see the studies for all other authors’ relevant financial disclosures.
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There were no significant associations between COVID-19 vaccination and adverse pregnancy outcomes in a cohort of pregnant women in Sweden and Norway, findings published in JAMA showed.
In another cohort study published in JAMA, data from Canadian women showed that there were no significant associations between vaccination during pregnancy and adverse peripartum outcomes.
Two recent studies — one in Scandinavia and another in Canada — showed that COVID-19 vaccination did not increase the risk for adverse pregnancy and peripartum outcomes. The findings suggest pregnant women should get vaccinated to protect against the adverse outcomes associated with infection, researchers said. Source: Adobe Stock
These studies add to the current well of data, which provides evidence that COVID-19 vaccination during pregnancy is safe — and even beneficial — for pregnant women and their babies.
“A few studies have investigated pregnancy outcomes in vaccinated individuals and did not find evidence of adverse maternal or neonatal outcomes,” Maria C. Magnus, PhD, a researcher at the center for fertility and health at the Norwegian Institute of Public Health in Oslo, Norway, and colleagues wrote in the first study. “However, these studies were based on a limited number of participants and were mostly hospital-based, or they were conducted during periods when vaccines were prioritized to high-risk groups and given to a restricted number of individuals.”
study outcomes
Using two national registries, Magnus and colleagues retrospectively analyzed 157,521 singleton births after 22 weeks’ gestation that occurred from Jan. 1, 2021, to Jan. 12, 2022, in Sweden and until Jan. 15, 2022, in Norway. They compared the risk for preterm birth, stillbirth, being born small for gestational age, low 5-minute Apgar score and neonatal care admission among the 28,506 vaccinated participants (18%) with that observed in unvaccinated participants.
In their analyses, Magnus and colleagues also identified in which trimester doses were administered.
The researchers who conducted the second study — Deshayne B. Fell, PhD, an associate professor in the school of epidemiology and public health at the University of Ottawa in Ontario, Canada, and colleagues — sought to fill the gap in comparative epidemiological data on vaccination’s impact on spontaneous abortion, preterm birth or being born small for gestational age.
In their population-based retrospective cohort of 97,590 participants who gave birth between Dec. 14, 2020, and Sept. 30, 2021, in Ontario, Fell and colleagues assessed the risk for outcomes including postpartum hemorrhage, cesarean delivery, chorioamnionitis, NICU admission and low 5-minute Apgar score in 22,660 participants (23%) who received a vaccine during pregnancy, 44,815 participants (46%) who started a vaccination series after pregnancy and 30,115 unvaccinated participants (31%).
For both studies, researchers only included vaccinated participants who had received at least one dose of the Pfizer-BioNTech, Moderna or AstraZeneca vaccines.
Vaccination data
Vaccinated participants in Norway and Sweden received their first dose at a median gestation of 209 days and 184 days, respectively. Of those who were vaccinated, 50.4% received their dose in the third trimester, 45.6% were vaccinated in the second and 3.9% were vaccinated in the first. Among all births in the study population, 4.8% were exposed to the Moderna vaccine, 12.9% had exposure to the Pfizer-BioNTech vaccine and 0.3% were exposed to the AstraZeneca vaccine.
Among participants in the Canadian cohort, 766 (3.4%) of those who were vaccinated only received one dose, 10,954 (48.3%) received one dose during and one dose after pregnancy and 10,940 (48.3%) received two doses during pregnancy. Similar to the European cohort, most participants (63.6%) vaccinated during pregnancy received their first dose in the third trimester, with a median gestation of 213 days. Also, 79.9% of vaccinated participants received the Pfizer-BioNTech vaccine for dose one, 19.9% received the Moderna vaccine and less than 1% received the AstraZeneca vaccine.
Risk for adverse outcomes
Magnus and colleagues identified no significantly increased risk for preterm birth with vaccination (6.2 vs. 4.9 per 10,000 pregnancy days at risk; adjusted HR = 0.98; 95% CI, 0.91-1.05), nor was vaccination significantly associated with stillbirth (2.1 vs. 2.4 per 100,000 pregnancy days; aHR = 0.86; 95% CI, 0.63-1.17) or being born small for gestational age (7.8% vs. 8.5%; adjusted OR = 0.97; 95% CI, 0.9-1.04).
In their comparison of participants vaccinated during and after pregnancy, Fell and colleagues found no significantly increased risk for postpartum hemorrhage (3% vs. 3%; adjusted risk difference [aRD] = 0.28 per 100 individuals; 95% CI, 0.59 to 0.03; adjusted RR = 0.91; 95% CI, 0.82-1.02), chorioamnionitis (0.5% vs. 0.5%; aRD = 0.04 per 100 individuals; 95% CI, 0.17 to 0.09; aRR = 0.92; 95% CI, 0.7-1.21) or cesarean delivery (30.8 % vs. 32.2%; aRD = 2.73 per 100 individuals; 95% CI, 3.59 to 1.88; aRR = 0.92; 95% CI, 0.89-0.95). The findings were similar when comparing participants vaccinated during pregnancy with those who were not vaccinated at all.
Neither study found a significantly increased risk for low 5-minute Apgar score (Magnus, 1.5% vs. 1.6%; aOR = 0.97; 95% CI, 0.87-1.08; Fell, 1.8% vs. 2%; aRD = 0.31 per
100 newborns; 95% CI, 0.56 to 0.06; aRR = 0.84; 95% CI, 0.73-0.97) or admission to neonatal care (Magnus, 8.5% vs. 8.5%; aOR = 0.97; 95% CI, 0.86-1.1; Fell, 11% vs. 13.3%; aRD = 1.89 per 100 newborns ; 95% CI, 2.49 to 1.3; aRR = 0.85; 95% CI, 0.8-0.9).
Implications and recommendations
In light of their findings, both research teams emphasized that pregnant women should be vaccinated to protect against the adverse outcomes associated with infection.
“COVID-19 vaccine effectiveness has been shown to be high in pregnant people, similar to the general population,” Fell and colleagues wrote. “Because COVID-19 vaccine-derived maternal antibodies cross the placenta, vaccination during pregnancy could potentially protect newborns in the early months of life, similar to well-established benefits of influenza and pertussis vaccination during pregnancy.”
Both sets of researchers stressed that women in their studies were primarily given mRNA vaccines during the second and third trimesters — something that should be taken into consideration when interpreting their findings.
References:
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