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Research Article Alert

COVID-19 mRNA Vaccine Safety in Pregnant People

 
Kelsey McLaughlin, PhD

On April 21st, 2021, The New England Journal of Medicine published a research article 'Preliminary Findings of mRNA Covid-19 Vaccine Safety in Pregnant Persons'. 

Pregnant persons & mRNA COVID-19 vaccines

 

COVID-19 is the disease caused by the recently discovered coronavirus, officially named the SARS-CoV-2 virus. There are currently 2 mRNA vaccines approved for use in Canada and the United States, produced by Pfizer Canada ULC/BioNTech SE and Moderna Therapeutics Inc.

Conscious Pregnancy has additional articles discussing COVID-19 in pregnant persons and COVID-19 vaccines & pregnancy.

 

As pregnant and breastfeeding persons were excluded from the Pfizer and Moderna COVID-19 vaccine clinical trials, there was initially little data evaluating the safety and efficacy of these COVID-19 mRNA vaccines in pregnant and breastfeeding persons.


This is especially concerning, as pregnant persons are at higher-risk of COVID-19 infection, relative to the general population. Since March 2020, scientific studies have shown that relative to non-pregnant women, pregnant persons with COVID-19 are at increased risk of not only severe respiratory and COVID-19 illness, but also higher rates of preterm delivery, Caesarean sections and delivering a low birthweight infant.

In addition, these poor pregnancy outcomes are more common in pregnant persons with severe COVID-19 infection, relative to persons with mild COVID-19 infection.

The Government of Canada, Society of Obstetricians and Gynaecologists of Canada (SOGC), American College of Obstetricians and Gynecologists (ACOG) and Centers for Disease Control (CDC) and Prevention recommend that pregnant or breastfeeding persons should be offered vaccination if they are eligible and no contraindications exist. The decision to receive the vaccine is based on person’s personal values and an understanding of the benefits and potential risks of vaccination.

Summary of the New England Journal of Medicine research article

Purpose

The safety of COVID-19 mRNA vaccines in pregnant persons was not formally assessed in clinical trials. This study reports the real world monitoring of mRNA COVID-19 vaccines in pregnant persons.

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Prenatal Yoga with Laptop

Methods

Data was collected through vaccine safety monitoring programs that have been developed in the United States. The main monitoring program was the The V-safe Surveillance System and Pregnancy Registry.

 

The V-safe Surveillance System and Pregnancy Registry is a new smartphone-based program created by the CDC for the COVID-19 vaccine program. People who received a COVID-19 vaccination during pregnancy or shortly before becoming pregnant were offered enrolment in to the system, which provided them with voluntary surveys to report side effects following vaccination​.

 

The authors of this study were interested in the safety of COVID-19 mRNA vaccines (Pfizer and Moderna) in pregnant people, looking at any potential relationships between COVID-19 vaccination and pregnancy outcomes, including pregnancy loss and neonatal outcomes. Vaccine side effects were compared between pregnant persons and non-pregnant women, all 16 to 54 years of age.

 

No statistical analysis was performed in this study; the authors chose to simply present the data and discuss any potential trends.

Results

 

Safety of COVID-19 mRNA vaccination in pregnant persons:

  • Number of pregnant persons: 35,691, most were pregnant at the time of COVID-19 vaccination

  • Majority of population: 25 – 34 years of age, non-Hispanic White

  • Common side effects following vaccination: injection-site pain, fatigue, headache and muscle pain

  • Side effects more frequent after the second dose of COVID-19 mRNA vaccination

 

Pregnancy and neonatal outcomes in pregnant persons following mRNA COVID-19 vaccination (table below):

  • Number of pregnant persons: 3,958

  • Majority of population: 25 – 44 years of age, non-Hispanic White, health care personnel, not diagnosed with COVID-19 during pregnancy

  • Timing of first dose of mRNA COVID-19 vaccine:

    • 2% prior to pregnancy

    • 29% in the first trimester

    • 43% in the second trimester

    • 26% in the third trimester

  • Pregnancy outcomes in 827 pregnant persons:

    • 86% had a live birth

    • 13% had a spontaneous abortion

    • 1% had induced abortion or ectopic pregnancy

    • 0.1% had a stillbirth

  • The most common adverse neonatal outcomes reported in the 724 live births:

    • 9% had a preterm birth

    • 3% were small for gestational age (3%)

    • 2% had major congenital anomalies - in pregnancies complicated by congenital anomalies, none of the pregnant persons had received COVID-19 vaccination prior to pregnancy or in the first trimester

    • No neonatal deaths were reported

  • In pregnancies complicated by congenital anomalies, none of the pregnant persons had received COVID-19 vaccination prior to pregnancy or in the first trimester

  • The frequency in pregnancy and neonatal outcomes following COVID-19 mRNA vaccination were similar to the frequency of these outcomes in pregnant persons prior to the COVID-19 pandemic - this table shows pregnancy and neonatal outcomes in pregnant persons before the COVID-19 pandemic (published incidence) and in pregnant persons who took the mRNA COVID-19 vaccine (v-safe pregnancy registry):

 

 

What do the results of this New England Journal of Medicine research article mean?

  • Pregnant people are choosing to receive COVID-19 mRNA vaccination in all trimesters of pregnancy

  • Side effects following COVID-19 mRNA vaccination are similar between pregnant persons and non-pregnant women

  • The rates of pregnancy complications after vaccination are similar to rates seen prior to the COVID-19 pandemic, suggesting that the COVID-19 mRNA vaccines do not increase the risk of pregnancy complications

  • The majority of pregnant persons who participated in these surveillance programs were white health care personnel that are not representative of the whole population of pregnant people; therefore, these results should be viewed as a directional guide of the potential for adverse outcomes following COVID-19 mRNA vaccination in pregnant people

  • Further enrolment in these surveillance programs and more detailed studies will capture a more diverse representative population and provide further evidence.

Summary

This New England Journal of Medicine research article provides data from COVID-19 vaccine surveillance systems following COVID-19 mRNA vaccination in pregnant persons. Preliminary findings did not suggest any obvious safety issues relating to pregnancy associated with COVID-19 mRNA vaccination.

 

Disclaimer

Every woman and every pregnancy is unique. Pregnant women should speak to their healthcare provider to ensure maternal and fetal safety. This article is meant to provide readers with current information and opinions. All medical and treatment decisions should be discussed with your healthcare provider.

This article was written by Dr. Kelsey McLaughlin and edited by Dr. Melanie Audette.

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