I always see these charts pop up on here in people's questions that show weeks pregnant and it…

I always see these charts pop up on here in people's questions that show weeks pregnant and it supposedly shows how many months pregnant you are and what trimester you're in. And it never fails someone has to correct someone else about it.... I'm a nursing student, so I by no means know everything, but this is how we learned it in clinicals: There's 40 weeks in pregnancy. That's actually 10 months, not 9. Each month has about 4 weeks in it. So count in multiples of 4 and that's how many months pregnant you are. I'm 21 weeks pregnant, so that means I've completed 5 months of pregnancy and I'm in the first week of my 6th month. Trimesters are different... There's 40 weeks, but to make it simpler, 39 weeks divided by 3 trimesters is 13 weeks in each trimester. 1-13 weeks is the 1st trimester. 14-26 is the second, and 27-39 (40) is the third.