COVID-19 vaccination does not increase the risk of pregnancy complications
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Women vaccinated against COVID-19 during pregnancy have no increased risk of pregnancy complications. These are the findings of a new international study of almost 160,000 births, conducted by researchers at the Norwegian Institute of Public Health (FHI) and the Karolinska Institute in Sweden.
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Pregnant women have a greater risk of becoming seriously ill with COVID-19, and COVID-19 during pregnancy can increase the risk of complications. It is therefore recommended that pregnant women are vaccinated against SARS-CoV-2.
Whilst smaller studies from other countries, and follow-up of vaccinated pregnant women, have not shown any risk associated with vaccination during pregnancy, larger studies comparing the risk of complications according to vaccination status among women pregnant during the same time are lacking. Pregnant women are also not included in clinical trials of vaccines before they have been approved. When introducing a new vaccine, it is therefore important to monitor pregnancy complications after vaccination.
In a large Nordic study published in the journal JAMA, data from health registries in Norway and Sweden were used to study whether vaccination against SARS-CoV-2 during pregnancy was associated with a risk of pregnancy complications.
The study included 157,521 births in Sweden and Norway between May 2021 and January 2022. Of these births, 18 percent were to mothers vaccinated against SARS-CoV-2 during pregnancy, mainly in the second and third trimesters, with one of the two available mRNA vaccines. The researchers looked at the risk of various pregnancy complications according to vaccination status.
The study found that women vaccinated against SARS-CoV-2 during pregnancy did not have an increased risk of the pregnancy complications examined, including preterm birth, stillbirth, reduced fetal growth, low general condition 5 minutes after birth and transfer to neonatal ward.
“These are reassuring results that support the current recommendation for pregnant women to get vaccinated against SARS-CoV-2,” says Maria C. Magnus, who is shared first author of the study and senior researcher at the Center for Fertility and Health.
The study was funded by Nordforsk and the Research Council Norway.
No difference according to timing or type of vaccination
There was no difference between the woman being vaccinated with Pfizer-BioNTech or Moderna's mRNA vaccine. There were also no differences between the woman who had been vaccinated in the second or third trimester of pregnancy.
The researchers could not study the risk of unfortunate pregnancy outcomes after vaccination in the first trimester, as this has not been recommended until recently, and few of these women have given birth yet. The research group has previously shown that there was no increased risk of miscarriage in women who were vaccinated in the first trimester.
“More information on the safety of vaccination of pregnant women against SARS-CoV-2 is still desirable, especially in the first trimester. It is also important to study whether COVID-19 infection in pregnancy or vaccination can affect the child's later health,” says Magnus.
Vaccination can protect the newborn from infection
Several studies suggest that the antibodies produced by the COVID-19 vaccine can be transmitted from mother to child during pregnancy. Therefore, children of mothers who were vaccinated during pregnancy may have a lower risk of infection in the first months of life, says Magnus.
None of the SARS-CoV-2 vaccines have yet been approved for children under five years of age. If vaccination of pregnant women can protect the newborn child from infection, this will strengthen the recommendation to vaccinate pregnant women.
Further research within an established Nordic collaboration
“Because recommendations change and new vaccines can be developed, we will continue to follow up on the safety of vaccination in pregnant women, and possible health consequences for mother and child,” says Magnus.
The researchers plan to continue the established research collaboration between the Nordic countries to follow up children of mothers who were vaccinated during pregnancy. The research group has previously published studies on the risk of infection in pregnant women and shown that pregnant women in Norway have an increased risk of being admitted to hospital if they have COVID-19.