The average human pregnancy lasts approximately 9 months, or more precisely, 280 days from the first day of the last menstrual period (LMP). This is commonly divided into three trimesters of roughly 3 months each. However, pregnancies are often measured in weeks rather than months, with a full-term pregnancy considered to be 37-40 weeks from conception. The variation in counting stems from the fact that conception typically occurs about 2 weeks after the LMP, so gestational age (measured from LMP) is about 2 weeks ahead of fetal age (measured from conception). Due to natural variation, most pregnancies last between 38-42 weeks before delivery, which is why doctors generally consider babies born between 37-42 weeks to be at term. Pregnancies that extend beyond 42 weeks are classified as post-term and may require medical intervention. The exact duration can vary based on individual factors, including the mother's health, whether it's a first pregnancy, and other circumstances. Knowing the expected due date helps healthcare providers monitor fetal development and plan for delivery appropriately.