Pregnancy Due Date

Tracking a developing pregnancy requires establishing a reliable chronological benchmark to schedule prenatal screenings, ultrasound appointments, and developmental milestones. Because the precise moment of conception is rarely known with certainty, obstetric medicine conventionally dates gestational progress from the first day of the last menstrual period. By entering the date of your last period and your typical cycle duration, you receive a standardized baseline for your obstetric calendar and pregnancy timeline.

The resulting estimate presents your projected estimated date of delivery along with your current gestational age expressed in completed weeks and days. Healthcare providers utilize these chronological markers to evaluate fetal growth rates and plan diagnostic testing throughout each trimester. It is important to remember that human gestation naturally varies, with only a small percentage of infants arriving on their exact due date, making ultrasound biometric confirmation essential for definitive clinical dating during early medical evaluations.

The calculation starts with the first day of your last menstrual period and adds 280 days, reflecting the standard 40-week human gestational cycle under Naegele's rule. It then adjusts the date by adding or subtracting the difference between your reported cycle length and a standard 28-day menstrual cycle. The resulting date identifies your estimated due date, while elapsed days from that baseline define current gestational age.