Emily Oster, PhD

2 minute read Emily Oster, PhD
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Emily Oster, PhD

Should I Avoid Swimming While Pregnant?

Q&A on infection risk

Emily Oster, PhD

2 minute read

My doctor told me that I shouldn’t swim during my first trimester due to the risk of unclean water and infection for the baby. I had never heard this before, and I can’t find anything that supports it. I am dying to get in the pool — please help!

—Kate

Bottom line: this prohibition makes no sense at all.

To take a charitable view of what your doctor might be thinking… Swimming in lakes or ponds can, in very rare cases, lead to health issues in general (not just in pregnancy). I can imagine, though I think it’s overkill, saying that pregnant people should be more careful about those settings.

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However, pools are not ponds. We have evidence from large cohort studies — for example, this one from Denmark with over 70,000 women — showing no link between birth defects and swimming. A second large study showed a similar thing. (In 2019, one paper argued that swimming pools might be associated with a slightly smaller child head circumference, but the empirical evidence in this paper is pretty unconvincing.)

On top of this body of evidence pointing to safety, there are good reasons to swim. ACOG recommends it as a top form of exercise (low impact, good aerobic workout, etc.). That large study from Denmark actually found a slightly lower risk of preterm birth among swimmers. At least one RCT from Europe showed that women who were randomized into a swimming program were less likely to have vaginal tearing during birth (no idea why the swimming would affect vaginal tearing, but that’s what showed up in the data).Swimming is great. I hope you can get back in the pool. The only caution — and you can take it from Olympic gold medalist Dana Vollmer, who was competing internationally at six months pregnant — is you’ll need a bigger suit.

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