Why doctors are so bad at predicting pregnancy due dates

https://www.vox.com/2018/6/9/17435322/pregnancy-due-date-test-premature-birth Only 4 percent of women give birth on their estimated delivery date. That’s because of the natural variation in how long it takes a baby to grow and because of our limited ability to predict due dates. Medicine, it turns out, is surprisingly bad at measuring the precise age of a fetus or how …