Due or born in September: when was the baby conceived?
A baby due in September was most likely conceived between 9 December and 7 January.
For a baby born in September at full term, from 37 to 42 weeks, conception was most likely between 25 November and 28 January.
Most likely conception date
Enter a date to see when conception most likely happened.
Not medical advice. Every pregnancy is different: ask your midwife or doctor about yours.
Conception date for each day in September
| Due date or birthday | Conception, for a due date | Conception, for a birth at 37 to 42 weeks |
|---|---|---|
| 1 September | 9 December | 25 November to 30 December |
| 2 September | 10 December | 26 November to 31 December |
| 3 September | 11 December | 27 November to 1 January |
| 4 September | 12 December | 28 November to 2 January |
| 5 September | 13 December | 29 November to 3 January |
| 6 September | 14 December | 30 November to 4 January |
| 7 September | 15 December | 1 December to 5 January |
| 8 September | 16 December | 2 December to 6 January |
| 9 September | 17 December | 3 December to 7 January |
| 10 September | 18 December | 4 December to 8 January |
| 11 September | 19 December | 5 December to 9 January |
| 12 September | 20 December | 6 December to 10 January |
| 13 September | 21 December | 7 December to 11 January |
| 14 September | 22 December | 8 December to 12 January |
| 15 September | 23 December | 9 December to 13 January |
| 16 September | 24 December | 10 December to 14 January |
| 17 September | 25 December | 11 December to 15 January |
| 18 September | 26 December | 12 December to 16 January |
| 19 September | 27 December | 13 December to 17 January |
| 20 September | 28 December | 14 December to 18 January |
| 21 September | 29 December | 15 December to 19 January |
| 22 September | 30 December | 16 December to 20 January |
| 23 September | 31 December | 17 December to 21 January |
| 24 September | 1 January | 18 December to 22 January |
| 25 September | 2 January | 19 December to 23 January |
| 26 September | 3 January | 20 December to 24 January |
| 27 September | 4 January | 21 December to 25 January |
| 28 September | 5 January | 22 December to 26 January |
| 29 September | 6 January | 23 December to 27 January |
| 30 September | 7 January | 24 December to 28 January |
In a leap year, the date moves by one day when 29 February falls between conception and the due date or birth.
Frequently asked questions
If our baby is due in September, when did we conceive?
A baby due in September was most likely conceived between 9 December and 7 January. That is 38 weeks (266 days) before the due date. The table on this page gives the date for each due date in the month.
Born in September: when was the baby conceived?
For a baby born in September at full term, from 37 to 42 weeks, conception was most likely between 25 November and 28 January. For a birth at exactly 40 weeks, it is the same date as for a due date that day.
Can a conception date settle a paternity question?
No. This is the textbook estimate. It cannot know your cycle, when you actually ovulated or how the pregnancy was dated, and it is not precise enough to tell apart two dates a few days apart.