gynecology and obstetrics
Physiology of Pregnancy
Introduction
The earliest sign of pregnancy and the reason most pregnant women initially see a physician is missing a menstrual period. For sexually active women who are of reproductive age and have regular periods, a period that is≥1 week late is presumptive evidence of pregnancy. Pregnancy is considered to last 266 days from the time of conception 280 days from the first day of the last menstrual period if periods occur regularly every 28 days Delivery date is estimated based on the last menstrual period. Delivery up to 2 weeks earlier or later than the estimated date is normal. Delivery before 37 weeks gestation is considered Preterm Labor ; delivery after 42 weeks gestation is considered 