Expecting Better: Why the Conventional Pregnancy Wisdom Is Wrong--and What You Really Need to Know

Oster tackles one of the most emotionally charged aspects of early pregnancy: loss. She begins by confronting the widespread statistic that pregnancy loss occurs in 15—20% of pregnancies, clarifying that this figure typically applies to recognized pregnancies—those confirmed by a test. When very early losses are included (such as those only detected by sensitive pregnancy tests), the rate can be significantly higher. Oster stresses that while pregnancy loss is common, it is not always discussed openly, leaving many who experience it unprepared and isolated.

Oster evaluates the most frequently cited risk factors, including caffeine, alcohol, exercise, and stress. She dissects each one using available studies. For caffeine, she finds that only very high levels, over 200-300 mg per day, is associated with increased risk; even then, however, the data is inconsistent and often confounded by nausea (since people with nausea tend to reduce caffeine intake and also have lower risk of losing a pregnancy). Of alcohol, she notes that, according to available data, heavy drinking clearly raises the risk, but moderate drinking (a few drinks per week) does not show strong evidence of harm. This is not an endorsement to drink, but does stray from ‘better safe than sorry’ principle on which most official guidance is based.