When is the baby due?
Your expected date of delivery and where you are in the 40 weeks, from the first day of your last period or from an early ultrasound scan.
How the due date is worked out
From the last period: the first day of the last period plus 280 days (40 weeks), known as Naegele's rule. For cycles longer or shorter than 28 days, the date moves by the difference.
From a scan: an ultrasound in the first trimester dates a pregnancy more exactly than the last period. Enter the scan date and the weeks and days it showed.
The due date is an estimate
Only about 1 in 20 babies arrive on their due date; most come within two weeks either side. The scans and tests listed are the usual ones; your doctor will plan your own.
Pregnancy by week
| Weeks | What usually happens |
|---|---|
| 1–13 | First trimester; an early (dating) scan fixes the due date most exactly |
| 11–13 | NT scan |
| 14–27 | Second trimester |
| 18–22 | Anomaly scan |
| 24–28 | Glucose test (OGTT) |
| 28–40 | Third trimester; from 37 weeks a baby counts as term, and 39 to 40 weeks is full term (ACOG) |
| 32–36 | Growth scan |
| 40 | Due date (280 days after the first day of the last period) |
Common questions
Which is more accurate, the last period or the scan?
An early scan, between about 8 and 13 weeks, is usually more accurate, especially when cycles are irregular. Doctors usually change the due date to the scan date if the two differ by more than 5 days (scan before 9 weeks) or 7 days (scan at 9 to 13 weeks), as ACOG advises.
When does each trimester start?
The first trimester runs to the end of week 13, the second to the end of week 27, and the third from week 28 until birth.
Is anything I enter saved?
No. The calculation happens on your phone and nothing is sent anywhere.
Reviewed by Dr. Herin Shah, MBBS on . For information; it does not replace a doctor's advice.
Sources
For doctors
Doccine does this for every patient in your clinic.
Doccine keeps the pregnancy record with the clinic's patients: pregnancy-safe checks on every prescription, and BP and weight watched at each antenatal visit.