COVID-19 vaccination during pregnancy was linked to a lower risk of neonatal intensive care unit (NICU) admission, stillbirth, and maternal SARS-CoV-2 infection and no additional risk of preterm birth, small for gestational age (SGA), low Apgar score, cesarean delivery, postpartum hemorrhage, or chorioamnionitis, finds a systematic review and meta-analysis published yesterday in JAMA Pediatrics.
Japanese researchers led the analysis of nine observational studies comparing the pregnancy outcomes of 81,349 women who received at least one COVID-19 vaccine dose with those of 255,346 unvaccinated peers through Apr 5, 2022. Average age was 32 to 35 years in the vaccinated group and 29.5 to 33 years in the unvaccinated group.
Among vaccinated women, 98.2% had received an mRNA vaccine (Pfizer/BioNTech, Moderna, or unstipulated), while 1.1% received a viral vector vaccine (Oxford/AstraZeneca or Johnson & Johnson), and 0.7% were undocumented.
In the six studies that reported the number of doses, 85.4% of women received two doses of an mRNA vaccine. Seven studies reported the timing of the first dose, with 5.9%, 46.3%, and 47.8% of women receiving their first dose during the first, second, and third trimester, respectively.
Maternal vaccination low worldwide
COVID-19 vaccination during pregnancy was tied to lower risk of NICU admission (odds ratio [OR], 0.88), stillbirth (OR, 0.73), and maternal SARS-CoV-2 infection (OR, 0.46) and no significant additional risk of preterm birth (OR, 0.89), SGA (OR, 0.99), low Apgar score (indicator of newborn needing medical attention; OR, 0.94), cesarean delivery (OR, 1.05), postpartum hemorrhage (OR, 0.95), or chorioamnionitis (infection of the placenta or amniotic fluid; OR, 0.95).
Four studies separately reported rates of preterm birth and SGA according to the timing of the first vaccine dose. The incidence of preterm birth and SGA was not significantly different between women vaccinated during the first trimester and their unvaccinated counterparts (ORs, 1.81 and 1.09, respectively). Vaccination during the second or third trimester relative to no vaccination, however, was tied to a lower risk of preterm birth (OR, 0.80) and SGA (OR, 0.94).
"Our data support the safety and efficacy of COVID-19 vaccination during pregnancy, facilitating the vaccination rates among pregnant individuals even if they do not get vaccinated before pregnancy," the study authors wrote.
Noting that COVID-19 infection during pregnancy is associated with adverse maternal and neonatal outcomes such as hospitalization, the need for intensive care, and death, the researchers said that clinicians should encourage pregnant women to be vaccinated against COVID-19.
But despite accumulating evidence of the safety and effectiveness of COVID-19 vaccination in pregnancy for mothers and babies, vaccination rates in this group remain low around the world. "Vaccine communication comprising education and recommendations can increase COVID-19 vaccine acceptance among pregnant individuals, as reported for tetanus-diphtheria-pertussis and influenza vaccines," the researchers wrote.
The team called for further large cohort studies with longer follow-up period to elucidate the long-term outcomes of COVID-19 vaccination during pregnancy and provide additional reassurance of its safety and efficacy in preventing poor outcomes.
