You would think so, but this is not accurate. Graphs for proportional rate of preterm birth vs mother's age: https://journals.plos.org/plosone/article/figure/im

You would think so, but this is not accurate. Graphs for proportional rate of preterm birth vs mother's age: https://journals.plos.org/plosone/article/figure/image?id=10.1371/journal.pone.0191002.g002&size=large https://journals.plos.org/plosone/article/figure/image?id=10... And rate of infant mortality vs mother's age: https://cdn.theatlantic.com/static/mt/assets/hua_hsu/cohen_infantmortality.png https://cdn.theatlantic.com/static/mt/assets/hua_hsu/cohen_i... Both have a minimum in the early 30s, a decade off from these numbers. Granted, there's likely some confounding due to poverty rates vs age of pregnancy, but the data simply does not support the conclusion that 20 is the best, healthiest age for a woman to bear a child. There's still some development and biological maturation going on into the 20s.