BABYFORECAST · GOOD TO KNOW
How accurate is your due date?
Your due date is a guide, not a reserved birthday. A chart can help explain the wait—but your baby has not accepted the calendar invitation.
What does the due date tell me?
Your estimated due date helps your care team place the pregnancy on a timeline. An ultrasound can contribute to dating. In Babyforecast, use the due date discussed with your care team.
What does the percentage in the free calculator mean?
If labour has not started at the beginning of the day, the calculator estimates the share starting that day. The comparison group includes only labours that eventually started on their own. Inductions and caesareans before labour are absent. The figure therefore offers statistical context within that group, rather than your personal probability.
The two additional figures show the share of the entire comparison group starting on that day or by the end of that day. Daily figures are calculated from published weekly shares.
What can I do already?
Free daily figures start at 37+0 weeks, 21 days before your due date. Before then, you can put your due date in context, choose a one-time reminder for EDD−21, or collect practical help through a baby wish list. A reminder does not start a newsletter subscription.
Does Pro use different figures?
Pro shows an outlook for up to seven days from 37+0 weeks. From 39+0 to 41+6 weeks, a separate study-informed model can use personal details when its prerequisites are confirmed: age, early BMI, previous spontaneous labour onset and conception method; a previous vaginal birth can contribute when earlier onset timings are unknown. The assumed model baseline without personal factors is for comparison only and is not the NICE distribution. Where no personal estimate is available, the historical NICE reference remains explicitly nonpersonal.
The combination of these effects is not clinically validated; greater accuracy has not been established. The separate calculator works only in this browser tab. For saved results and optional emails, explicitly enable the model in your Pro profile. Your account and email then use the same calculation for the same details and day.
Labour onset is not the birthday
The reference describes spontaneous labour onset, not the birth date or a separately predicted rupture of membranes. Induction and caesarean are not predicted.
When is a percentage not helpful?
A low number does not rule out labour or a problem. If your baby moves less than usual, you have bleeding, suspect your waters have broken, or have other concerns, contact your care team or maternity unit promptly—immediately for those warning signs. Do not wait for a different calculator result.