Preliminary Findings of mRNA Covid-19 Vaccine Safety in Pregnant Persons

N Engl J Med. 2021 Jun 17;384(24):2273-2282. doi: 10.1056/NEJMoa2104983. Epub 2021 Apr 21.

Abstract

Background: Many pregnant persons in the United States are receiving messenger RNA (mRNA) coronavirus disease 2019 (Covid-19) vaccines, but data are limited on their safety in pregnancy.

Methods: From December 14, 2020, to February 28, 2021, we used data from the "v-safe after vaccination health checker" surveillance system, the v-safe pregnancy registry, and the Vaccine Adverse Event Reporting System (VAERS) to characterize the initial safety of mRNA Covid-19 vaccines in pregnant persons.

Results: A total of 35,691 v-safe participants 16 to 54 years of age identified as pregnant. Injection-site pain was reported more frequently among pregnant persons than among nonpregnant women, whereas headache, myalgia, chills, and fever were reported less frequently. Among 3958 participants enrolled in the v-safe pregnancy registry, 827 had a completed pregnancy, of which 115 (13.9%) resulted in a pregnancy loss and 712 (86.1%) resulted in a live birth (mostly among participants with vaccination in the third trimester). Adverse neonatal outcomes included preterm birth (in 9.4%) and small size for gestational age (in 3.2%); no neonatal deaths were reported. Although not directly comparable, calculated proportions of adverse pregnancy and neonatal outcomes in persons vaccinated against Covid-19 who had a completed pregnancy were similar to incidences reported in studies involving pregnant women that were conducted before the Covid-19 pandemic. Among 221 pregnancy-related adverse events reported to the VAERS, the most frequently reported event was spontaneous abortion (46 cases).

Conclusions: Preliminary findings did not show obvious safety signals among pregnant persons who received mRNA Covid-19 vaccines. However, more longitudinal follow-up, including follow-up of large numbers of women vaccinated earlier in pregnancy, is necessary to inform maternal, pregnancy, and infant outcomes.

MeSH terms

  • Abortion, Spontaneous / epidemiology
  • Adolescent
  • Adult
  • Adverse Drug Reaction Reporting Systems
  • COVID-19 Vaccines / adverse effects*
  • COVID-19 Vaccines / immunology
  • Female
  • Humans
  • Infant, Newborn
  • Infant, Small for Gestational Age
  • Middle Aged
  • Pregnancy*
  • Premature Birth / epidemiology
  • Public Health Surveillance / methods
  • Registries
  • United States / epidemiology
  • Vaccines, Synthetic / adverse effects
  • Young Adult
  • mRNA Vaccines

Substances

  • COVID-19 Vaccines
  • Vaccines, Synthetic