According to analysis from data journalism website FiveThirtyEight, birth rates are lower than expected on the 13th of any month, and especially low when it falls on a Friday.
FiveThirtyEight ran data from the National Center for Health Statistics and the Social Security Administration from 1994 through 2014, comparing birth rates from the 6th and 20th of every month to birth rates on the 13th of every month. They excluded months in which a major holiday fell on those dates.
What they found was lower-than-expected birth rates on the 13th, no matter what day it fell on, and especially low birth rates on Friday the 13th.
"Many births are scheduled… And, given the choice, lots of parents would rather not take their chance with a date that delivers a double whammy of superstitious bad luck, tying together longstanding fears about Fridays and the number 13," Carl Bialik of FiveThirtyEight wrote.