how many weeks is 9 months pregnant?

How Many Weeks, Months and Trimesters in a Pregnancy?
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by
Colleen de Bellefonds
Medically Reviewed by James Greenberg, M.D. on May 17, 2022
Stocksy
pregnant woman calculating due date on tablet
You can hardly wait until your due date — but when is it again? Find out exactly how many weeks and months into pregnancy you are.
In This Article

How many weeks are in a pregnancy?
How many weeks are in a trimester?
How many trimesters are in a pregnancy?
Is pregnancy nine or 10 months long?
How many weeks is a full-term pregnancy?
Pregnancy months to weeks chart
How do I know what week I am currently in my pregnancy?

Your pregnancy countdown can get jumbled pretty quickly. Are you 13 weeks pregnant or in week 14? First trimester or your second? Three months pregnant or four?

Fortunately, the answers are (relatively) simple once you know what to count. Here’s what you need to know about how many weeks, months and trimesters there are in a pregnancy — and where you fit in.
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How many weeks are in a pregnancy?

There are 40 weeks (or 280 days) in a pregnancy. Your due date is calculated starting from the first day of your last menstrual period (even though most pregnancies are not conceived until two weeks later). Keep in mind that only about 30 percent of pregnancies will reach precisely week 40.
How many weeks are in a trimester?

There are 13 or 14 weeks per trimester. (Just divide 40 by three and you’ll see why the breakdown isn’t exact.)
How many trimesters are in a pregnancy?

There are three trimesters in a pregnancy: the first trimester, which lasts from weeks 1 to 13, the second trimester, which lasts from week 14 to week 27, and the third trimester, which lasts from week 28 to week 40 (and up).
Is pregnancy nine or 10 months long?

Your 40 weeks of pregnancy are counted as nine months. But wait … there are four weeks in a month, which would make 40 weeks 10 months. Right? Not exactly.

Four weeks is 28 days, but months (with the exception of February, of course) have 30 or 31 days, making each month about 4.3 weeks long.
How many weeks is a full-term pregnancy?

If you're carrying a single baby, a full-term pregnancy is between the start of 39 weeks up to the end of 40 weeks. If you're carrying twins, a full-term pregnancy is considered at least 38 weeks.