There’s a lot of stigma and confusion around the use of substances in pregnancy. In perhaps the most provocative part of Expecting Better, Oster argues that caffeine and alcohol, in moderation, show no evidence of being harmful to the child.
Caffeine During Pregnancy
The concern with caffeine is that it can increase the risk of miscarriage and limit blood flow to the placenta.
The evidence is mixed – some studies find a 25% miscarriage rate for >200mg caffeine a day (about 1-2 cups of coffee), and a 13% miscarriage rate for less caffeine consumption. High rates of caffeine (>5 cups of coffee a day) more consistently led to a 50-100% increase in the risk of a miscarriage.
Other studies find no relationship in miscarriage or baby health. Tea and cola are less consistently linked with miscarriage than coffee, which is odd since they all have caffeine as the active ingredient. Furthermore, decaf coffee may be as strongly linked to miscarriage as regular coffee.
Oster argues that caffeine pregnancy studies have a big confound with nausea. Nausea is apparently a good sign about the health of the pregnancy and indicates a lower risk of miscarriage. However, you’re less likely to drink coffee when nauseated. So women who drink caffeine may simply be less nauseous and become more likely to have miscarriages.
Oster believes it’s completely safe to have up to 2 cups of coffee a day, and probably OK to have 3-4 cups. Beyond that, the evidence is mixed and may be confounded with nausea.
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- Why much parenting advice you hear is confusing or nonsense
- The most reliable way to conceive successfully
- How much alcohol research shows you can drink safely while pregnant (it's more than zero)
- The best foods to eat, and what foods you really should avoid