How many pregnancy months are there – nine or ten? A typical pregnancy lasts approximately 38-42 weeks and is divided into three, three-month long trimesters. Sounds like nine pregnancy months, right?

Others insist that pregnancies are considered full term at 40 weeks and generally, women count four weeks as a month while they are pregnant. Therefore, many people consider pregnancy to actually last ten months. Another way to look at it is from the lunar calendar. Prenatal development is often measured in lunar months. Each lunar month consists of 28 days, organized into four weeks of seven days each. That means, using a lunar calendar, there are ten pregnancy months.

Certified nurse midwife Nancy Sullivan explains it this way: “The average pregnancy has 280 days, 40 weeks, or 9 months plus 1 week, counted from the first day of the last menstrual period. In other words, we start counting about two weeks before the baby is actually conceived.”