Pregnancy typically lasts about 40 weeks, which is approximately 280 days from the first day of the woman's last menstrual period. This 40-week period is considered the full term of pregnancy

. Key points about pregnancy duration:

• The 40 weeks are counted starting from the first day of the last menstrual period, not from conception, which usually occurs about two weeks later

• Pregnancy is divided into three trimesters:
  • First trimester: conception to 12 weeks
  • Second trimester: 13 to 27 weeks
  • Third trimester: 28 to 40 weeks

• Babies born before 37 weeks are considered preterm or premature, while those born between 37 and 42 weeks are considered full term

• Labor usually begins within a week before or after the 40-week mark, but some pregnancies can go up to 42 weeks before labor starts

In summary, a normal pregnancy lasts around 40 weeks from the last menstrual period, with full term considered between 37 and 42 weeks.