Using Statistics to Predict a Baby’s Due Date Beats Traditional Method

“Most doctors don’t even give the most accurate prediction of the due date. They still often calculate the due date based on the quasi-mystical formula of Franz Naegele, who believed in 1812 that ‘pregnancy lasted ten lunar months from the last menstrual period.’ It wasn’t until the 1980s that Robert Mittendorf and his coauthors crunched numbers on thousands of births to let the numbers produce a formula for the twentieth century. Turns out that pregnancy for the average woman is eight days longer than the Naegele rule, but it’s possible to make even more refined predictions. First-time mothers deliver about five days later than mothers who have already given birth. Whites tend to deliver later than nonwhites. The age of the mother, her weight, and her nutrition all help predict her due date. Physicians using the crude Naegele rule cruelly set up first-time mothers for disappointment.” (p. 209)