About 1 in 20 women give birth on their estimated due date, according to ACOG’s patient guidance. That is about 5%. It is a general statistic, not a prediction of when an individual baby will arrive.
A due date marks an estimated 40 weeks of pregnancy. It helps the maternity team track gestational age and plan care; giving birth on another day does not by itself mean the date was calculated incorrectly. Use our pregnancy due date calculator as a calendar estimate and follow the date and care plan recorded by your clinician.
What the percentage does—and does not—tell you
Five percent means approximately five out of 100 in the population described. It does not mean each remaining day has the same chance of birth, or that the other 95 births are late. Some occur before the due date and some after it. A scheduled delivery date and an estimated due date are also different things.
A useful due-date statistic needs a clearly defined group: all births or spontaneous labour, singleton or multiple pregnancies, first or later births, and how gestational age was established. Mixing those groups can produce misleading percentages. This page does not assign personal odds to the week before or after your date.
How the estimate is established
A calendar calculation starts from the first day of the last menstrual period. Uncertain period dates or a cycle that differs from the calculator’s assumptions can change the estimate. The NHS due-date guidance explains that a dating scan can estimate gestational age more accurately. Tell your maternity team if your dates are uncertain or your pregnancy followed fertility treatment.
Do not keep changing your recorded due date to match later size measurements or a different online calculator. Ask the clinician who established it to explain any discrepancy. See our guide to how a due date is calculated for the calendar arithmetic.
Full term has a specific meaning
The phrase “full term” does not cover every pregnancy from 37 through 42 weeks. ACOG and SMFM use these categories:
| Category | Gestational age |
|---|---|
| Early term | 37 weeks 0 days through 38 weeks 6 days |
| Full term | 39 weeks 0 days through 40 weeks 6 days |
| Late term | 41 weeks 0 days through 41 weeks 6 days |
| Postterm | 42 weeks 0 days onward |
These labels describe gestational age. They are not a timetable for deciding whether to wait, arrange induction, or change an appointment.
A worked calendar example
Suppose the maternity record gives 14 November 2026 as the estimated due date. That day is 40 weeks 0 days. Seven days earlier, 7 November, is 39 weeks 0 days. Seven days later, 21 November, is 41 weeks 0 days. The subtraction tells you gestational age; it does not give the probability of birth on any of those dates.
When planning leave, transport or family support, separate the estimated date from your appointments and any planned delivery. Write down:
- The due date recorded by your maternity team and how it was established.
- Your next appointment and the plan if pregnancy continues beyond that date.
- The maternity contact number and the instructions you have been given about when to call.
Questions to take to your maternity appointment
- Was my date established using my period, a dating scan, or fertility-treatment information?
- Does the date in my record match the one I am using for planning?
- What is my individual follow-up plan if I reach or pass the due date?
For clinical decisions, including monitoring or induction, use your maternity team’s advice. This is an educational explanation of dates and population statistics, not a medical assessment or a clinician-reviewed care plan. ACOG’s guidance on pregnancy past the due date explains why an individual plan matters.
Correction, 1 October 2026: Removed unsupported birth-window percentages and replaced an overly broad definition of full term with the published gestational-age categories.
Related: Counting pregnancy weeks · Editorial policy · Report an error