And periods are two weeks late sometimes! People's periods aren't always regular or predictable. As someone who was tracking pretty obsessively for a number of years trying to conceive, even a very consistent cycle can fluctuate 10 days without medical concern.

Not to mention that many people who get abortions are in their 40s and already have children. Perimenopause can start making your period VERY wonky, even if it was regular for most of your life. I switched from an IUD to birth control pills at about 45 just to make my period more regular!