In 2021, amid the COVID‑19 pandemic, Kristin Wall became pregnant with her second child. Her physician told her that little was known about the COVID-19 vaccine’s safety and effectiveness in pregnant people. Observational data — collected from those vaccinated before they knew that they were pregnant — suggested that the vaccine was safe, so she could have it. Still, she’d have to weigh up the risks and benefits herself.
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Wall is an epidemiologist at Emory University in Atlanta, Georgia, and is therefore unusually qualified to assess health risks. But her experience is a common one — and far from unique to COVID-19. When it comes to pregnancy, people must often make important medical decisions with limited or imperfect information, says Wall. Pregnancy changes the body, including how it metabolizes and distributes medications, so a drug with a predictable effect in a non-pregnant person might work very differently in someone who is pregnant.
There is now solid evidence from the huge numbers of people vaccinated, and subsequent clinical trials, that the COVID-19 vaccines that use messenger RNA (mRNA) — as well as influenza vaccines and others that do not use live viruses — are generally safe and effective during pregnancy. Safety is also well established for certain other medications: some anti-allergy drugs, some antidepressants and some antibiotics are considered safe for use in pregnancy. Paracetamol (acetaminophen) — the main ingredient in Tylenol — is also considered safe, despite claims to the contrary by US President Donald Trump. Other drugs, however, are known to carry risks. An example is the anti-epilepsy drug sodium valproate, which can cause severe developmental disorders when taken during pregnancy.
Most people take medications during pregnancy — more than 90% in the United States according to some tallies1. Despite this, the safety and effectiveness of many drugs — including some anti-nausea treatments, some anti-inflammatories and the vast majority of medicines approved over the past decade — remain uncertain because they have never been tested in pregnant people. Fears over adverse consequences and associated policy restrictions mean that pregnant people have been largely excluded from clinical trials. That leaves public-health officials and health-care providers basing recommendations on indirect evidence, including animal studies, trials in non-pregnant people and observational studies of pregnant people taking a drug after it is already on the market.
“The gap is huge,” says Wall. She and others have designed trials that have successfully tested treatments for Ebola, HIV and some pregnancy-specific conditions in pregnant people — collecting reliable data while protecting the health of study participants and their babies. Based on that experience, they have developed tools and guidance to help other researchers to include pregnant people in studies, too. But despite these advances, logistical, regulatory and ethical barriers remain.
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There’s no evidence yet that Trump-era policies, such as the ‘Make America Healthy Again’ movement, have reduced the inclusion of pregnant people in trials, Wall says. But she adds that the broader increase in anti-pharmaceutical rhetoric might reinforce long-standing hesitancy to study medications in pregnancy — slowing efforts to close evidence gaps.
For Denise Astill, who took sodium valproate during pregnancy before clear guidance advised against its use, real progress “is about equity”. Her twin daughters were diagnosed at the age of four with a wide range of health conditions, including cognitive difficulties, hearing problems, kidney impairment, autism and attention deficit hyperactivity disorder.
Her experience led her to found the charity Foetal Anti-Convulsant Syndrome New Zealand in Auckland, which offers guidance on taking anti-seizure medications in pregnancy. Pregnant people should have the same access to evidence-based care as everyone else, she says. “Can we truly make an informed choice when our health system and research are based on men?”
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