When does third trimester start?

Question

I looked it up but I’m finding two different answers... I’m 27 weeks preg and just curious on if I’m still in second trimester until 28 weeks or has third trimester already begin? Here are 2 pics I found online, with one saying third trimester starts at 27 weeks and the other day 28 weeks. What do you consider third trimester?

Answer

It’s because pregnancy is considered to be 40 weeks and 40 cannot be divided by three in whole weeks. So every trimester is 13 weeks and the ‘leftover week’ is added in either trimester. 
When you take 27 weeks as the start of the third trimester, the first and second trimester are 13 weeks and the third trimester is 14 weeks. If you take 28 weeks as the start of the third trimester, either the first or second trimester counted 14 weeks and the other and the third trimester are 13 weeks.

Answer

Pregnancy is 40 weeks. Divided by 3, each trimester is 13.333333 weeks long. So 3rd trimester starts at 26.6666667 weeks

Answer

End of 26 weeks beginning of 27

Answer

I’m 26 weeks pregnant I’m going by the first picture 😂😂helps me move the pregnancy along

Answer

I say 27 or 28 weeks

When does third trimester start?

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