Pregnancy typically lasts about 40 weeks, which is roughly 10 months when counted from the first day of the woman's last menstrual period. This counting includes about two weeks before actual conception occurs, so although pregnancy is often said to last nine months, medically it is considered 40 weeks or 280 days long. Full-term pregnancy is generally between 39 weeks and 40 weeks and 6 days, and labor is usually induced if the pregnancy extends beyond 41 to 42 weeks. The pregnancy period is divided into three trimesters, each lasting around 13 to 14 weeks.
