Only a politician could come up with 14 as a trimester.
9 months X 4 is 36 weeks. Divided by three is 12.
12, 14, 15...tomato, tomato, let’s call the whole thing off!
😉
I’m sure that you are aware that nearly all months are more than 28 days. Seven of them by almost half a week. Over time the extra 2.5 average days adds up to additional weeks. 9 months comes to about 39 weeks, and the 9 month mark is a little short of the actual 40 week or so average gestation periods for humans.