Final answer:
A woman is typically pregnant for about 40 weeks, which is divided into three trimesters of approximately 13 weeks each, with labor generally starting around the 40-week mark.
Step-by-step explanation:
The average duration of a pregnancy is 40 weeks, beginning from the first day of the last menstrual period (LMP) and concluding at childbirth. This period is customarily divided into three trimesters, each spanning approximately 13 weeks. The first trimester includes the initial 12 weeks when some women may experience morning sickness.
The second trimester spans from weeks 13 to 28, during which many women feel increased energy and start to feel the fetus's movements around week 20. Finally, the third trimester extends from weeks 29 to birth at around 40 weeks, wherein rapid uterine growth and physical changes are experienced by the pregnant person. Labor typically begins around the 40-week mark and is described through stages, with the birth of the baby as the focal event.