BACKGROUND AND PURPOSE:

• The clinical trials for mRNA-based COVID-19 vaccines did not include any pregnant women, so safety data in this group was initially limited
  • However, many pregnant women in the general population have since received these vaccines, providing a cohort in which to assess safety data
• Shimabukuro et al. (NEJM, 2021) reported preliminary findings regarding mRNA COVID-19 vaccine safety in pregnant persons from three U.S. vaccine safety monitoring systems

METHODS:

• Setting
  • United States
  • Data from December 14, 2020, to February 28, 2021
• Data sources
  • The “V-safe after vaccination health checker” surveillance system
  • The V-safe pregnancy registry | Telephone-based survey collects detailed information
  • The Vaccine Adverse Event Reporting System (VAERS)
• Primary outcomes
  • Non–pregnancy-specific adverse events
  • Pregnancy- and neonatal-specific adverse events

Note: Pregnancy and neonatal outcomes were derived from patients who enrolled in the registry

RESULTS:

• 35,691 v-safe participants self-identified as pregnant
  • Majority of the participants were
    • Between 25 to 34 years of age | Non-Hispanic White (approximately 75%)
• 3958 participants were enrolled in the registry

Vaccine-related side effects (V-safe)

• Injection-site pain was reported more frequently among pregnant women than among nonpregnant women
• The following were reported less frequently among pregnant women
  • Headache
  • Myalgia
  • Chills
  • Fever

Pregnancy Outcomes

• 827 participants completed pregnancy
  • Live birth: 86.1%
  • Spontaneous abortion: 12.6%
  • Stillbirth (0.1%)
  • Other outcomes (induced abortion and ectopic pregnancy): 1.2% 

Neonatal Outcomes

• Preterm birth: 9.4%
• Small for gestational age: 3.2%
• There were no neonatal deaths

Adverse Events (VAERS)

• 221 reports
  • Nonpregnant related: 70.1%
  • Pregnancy related: 29.9%
• Most frequently reported pregnancy-related adverse events
  • Spontaneous abortion (37 first trimester, 2 second trimester, 7 unknown or not reported)
  • No congenital anomalies (EUA reporting requirement)

CONCLUSION:

• While not directly comparable, the proportions of adverse outcomes in vaccinated women were similar to those reported in studies involving pregnant women before the pandemic
• Further longitudinal study is important, especially in women vaccinated in the first trimester
• The authors conclude that

Early data from the v-safe surveillance system, the v-safe pregnancy registry, and the VAERS do not indicate any obvious safety signals with respect to pregnancy or neonatal outcomes associated with Covid-19 vaccination in the third trimester of pregnancy

Learn More – Primary Sources:

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

Related ObG Topics:

Safety and Efficacy Data of BNT162b2 COVID-19 Vaccine

The Moderna Vaccine: Study Results Presented to ACIP CDC Committee

Vaccines in Pregnant and Lactating Women: Is Immune Response Similar to that of Non-Pregnant Patients?

COVID-19 mRNA Vaccine Effectiveness in the Real World Including in Those Partially Immunized