How Far Along Are You? Counting Pregnancy by Weeks, Months & Trimesters

Measuring Your Pregnancy

How Many Weeks?

Many people first report their pregnancy progress in weeks. The date and progress of your pregnancy is measured from the start date of your last menstrual period (LMP). The week of your last period before finding out you’re pregnant is technically considered the first week of pregnancy even though you aren’t actually pregnant at that time. This dating method is easier to use since it’s practically impossible to know the exact date of when sperm met egg. Even if you know when you ovulated or when sperm was introduced, it’s impossible to know when conception occurred since sperm can live in the uterus up to five days. 

Pregnancy lasts around 40 weeks, give or take. Since the body doesn’t stick to deadlines or guidelines, 40 weeks is just an estimate. Many people give birth before or after that time. First-time parents often go into labor closer to 41 weeks.

How Many Months?

The average calendar month is 4-5 weeks, but a pregnancy month is always exactly 4 weeks. If you’re 32 weeks pregnant, you would say you’re 8 months pregnant even if some of the calendar months were closer to 5 weeks long. 

Weeks into Months, Months into Trimesters

It wasn’t enough to count a pregnancy by weeks or months — we had to introduce trimesters! A trimester is a period of 3 months, and each pregnancy contains 3 trimesters. Each trimester marks a different developmental stage of your baby’s growth in utero. Often, there are a different set of symptoms attributed to each of the trimesters, too. 

Putting It All Together

We created a handy little chart to help you identify exactly where you are in your pregnancy in weeks, months, and trimesters.