The average time of gestation (medical-speak for pregnancy) is 266 days or 38 weeks or 9.5 months.
But isn’t pregnancy 40 weeks or nine months long?
Sort of, but not really. Actual pregnancy-- where you’re living life as a human pod, lasts about 38 weeks from conception to birth. Two weeks are added to the pregnancy timeline by calculating back from the first day of your last menstrual period.
The first part of your due date calculation reflects the time span in which your body prepares for and engages in ovulation, after which conception occurs -- some two weeks after the first day of your last menstrual period.
This means you're given a full 40 weeks of pregnancy rather than the 38 weeks of gestation you actually physically experience (266 days from implantation to birth).
For the majority of women who’re not actively playing the baby-making game, their pregnant state is only realized some 4-8 weeks into the game when their period fails to show as expected.
So, even though you’re literally carrying a child for 38 weeks it’s likely you’re only aware of this fact for some 32 of those weeks -- which is more like 8 months of pregnancy that you're aware of before labor and birth.
Research indicates that approximately 90% of women carry their baby to term (37 weeks) before giving birth. The remaining 10% go into premature labor for a variety of reasons such as gestational diabetes, placental complications, hormonal imbalances, and a variety of other rarer conditions.