Pregnancy is traditionally measured in weeks rather than months because it provides a more precise way to track fetal development and medical milestones. A full-term pregnancy lasts about 40 weeks, starting from the first day of the last menstrual period (LMP). While many people ask, “How many months am I?” doctors and midwives rely on weeks since months vary in length and don’t align perfectly with the stages of pregnancy. For example, saying someone is “six months pregnant” could mean anywhere from 23 to 27 weeks, depending on how one calculates it. This is why healthcare providers use weeks and trimesters to monitor pregnancy progress accurately.
When thinking about pregnancy in months, it’s helpful to remember that 40 weeks doesn’t divide evenly into nine months—which is why this method can be confusing. The first trimester covers weeks 1 to 13, the second trimester is from 14 to 27 weeks, and the third trimester lasts from 28 to 40 weeks (or until birth). While it’s common to hear someone say they’re “three months along,” medical professionals would say “12 weeks,” which is much more precise. By focusing on weeks, we can better track fetal growth, developmental milestones, and important tests or screenings that happen at specific times. So, next time you’re wondering how far along you are, think in terms of weeks rather than months—it’s how pregnancy is truly measured!
