Covid-19 associated with an increase in stillbirths.

A new study shows the Delta variant has made things worse.

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A higher rate of stillbirths is associated with Covid-19 during pregnancy, a large new study has found. The risk of stillbirth among women who had Covid-19 during pregnancy was nearly double that of those who did not have Covid-19 while pregnant. The study covered outcomes from March through September of 2021. During the Delta-variant era, the risk was higher, with approximately four-times more stillbirths born to mothers who had Covid-19 during pregnancy than to those who remained Covid-19-free. In purely numeric terms, around 1 in 160 pregnancies ended with a stillbirth among Covid-19-free mothers (which matches usual rates from decades of existing data), compared to around 1 in 40 among mothers who had acquired Covid-19 while pregnant. The results of the new study published in the Centers for Disease Control and Prevention’s Morbidity and Mortality Weekly Report, summarizing data from over 1.27 million deliveries in the United States.

We already knew that Covid-19 is particularly dangerous to unvaccinated pregnant women, increasing maternal mortality by more than 20-fold. But one of the marvels of evolution is that recently infected pregnant women have been found to pass along Covid-19 antibodies to their fetuses, but not the virus itself. (The umbilical cord and placenta routinely function in this way, meaning that in general infants are likely to be born with protection from a recent illness that the mother had, without ever having to be infected with the illness itself). Because of this, until now, the complications of Covid-19 that fetuses and infants have experienced have been less frequent and less dire than those endured by their mothers. However, known birth complications related to maternal Covid-19 illness appear to include higher rates of pre-maturity (which comes with its own risks) and more frequent episodes of “fetal distress” around the time of delivery. There had been mounting though relatively thinner evidence that stillbirths might be associated with Covid-19 during pregnancy. The design and size of this latest study now makes the connection essentially irrefutable.

While we do not know what percent of the women included in the new study who had stillbirths were vaccinated, vaccination rates among pregnant women have been woefully low, landing between 30-35% at last check, with minority populations trailing far behind. While breakthrough Covid-19 among pregnant patients is of course possible, I have seen no data suggesting that the same risks that unvaccinated pregnant women face continue to apply to vaccinated ones. (However, in a future Inside Medicine I will discuss why and when pregnant women should receive boosters).

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Why have vaccination rates among pregnant women been so low? It’s likely a combination of knowledge-related hesitancy (i.e. women have important questions that they need answered) and outright misinformation and disinformation. In one study, 36% of pregnant women cited questions about safety and effectiveness of the Covid-19 vaccines as a reason for their hesitancy. While such questions were certainly understandable early in the vaccine rollout—especially since pregnant women were not specifically included in the clinical trials—we now can answer most of the questions pregnant women need answered with troves of data we have collected since. Meanwhile, misinformation and disinformation remain a problem. Despite strong statements from the American College of Obstetricians and the Society for Maternal-Fetal medicine (including the threat of disciplinary actions against physicians who spread of false information), many in the general public continue to believe the cynical anti-vaccine hoax that Covid-19 vaccines somehow cause infertility. Not only is that patently untrue, in a sense, the opposite is true. Covid-19 kills some pregnant women and is associated with higher stillbirth rates. What could be more detrimental to fertility than the death of a mom or an infant?

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The case for vaccines in pregnancy is closed. Any woman who is pregnant, or who might soon be, is placing themselves and their fetuses at grave risk by not receiving a Covid-19 vaccine. But the one upside of women of childbearing intent who have waited and not yet been vaccinated, is that they can safely receive three doses during their 9-month pregnancies if they are vaccinated early enough. Receiving the initial two doses of Pfizer or Moderna in the 1st trimester is safe and provides protection to both the mother and the fetus. Then, a booster during the 3rd trimester may add some benefit to the mother (although again, I have not yet seen evidence that breakthrough infection to pregnant women is remotely as dangerous as unvaccinated infection). The result of receiving all three vaccines during pregnancy is high rates of protection to both mothers and also fetuses; eventual infants will have the added protection for several months after birth by virtue of booster-derived antibodies.

Clearly my goal in writing this is to inform my readers and therefore to increase the chances that someone seeing this who is pregnant (or who might soon become pregnant) will close this browser (after helping me share it online) and do a quick-and-easy search for a place to get their Covid-19 vaccine. I hope it helps.

I’ll address Covid-19 boosters for already-vaccinated women who might become pregnant in a newsletter in the near future.

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