Due Date March 17: When Did You Conceive?
Wondering when your March 17 baby was conceived? Using the standard 266-day rule, the answer is most likely June 24 of the previous year, give or take a few days.
Key dates for a March 17 due date
| Most likely conception date | June 24 |
|---|---|
| Likely conception window | June 21 – June 27 |
| Days when sex could have led to pregnancy | June 19 – June 25 |
| Estimated first day of last period | June 10 |
| Positive home test likely from | July 8 (around the missed period) |
| Second trimester begins (14 weeks) | September 16 |
| Third trimester begins (28 weeks) | December 23 |
| Full term begins (39 weeks) | March 10 |
How the conception date is calculated
Due dates are normally counted as 280 days (40 weeks) from the first day of the last menstrual period. In a typical 28-day cycle, ovulation and conception happen about two weeks after that period starts, so conception sits roughly 266 days before the due date. Subtracting 266 days from March 17 gives June 24.
Sperm can survive in the reproductive tract for up to five days, while an egg lives for about 12 to 24 hours after ovulation. That means sex several days before ovulation can still lead to pregnancy.
How certain is this date?
Remember that a due date is only the midpoint of a range. Ovulation timing varies from cycle to cycle, so the true conception day can sit a few days away from the estimate.
If your cycles are usually longer than 28 days, conception probably happened a little later than June 24; with shorter cycles, a little earlier. A cycle that is 32 days long, for example, shifts the likely date about four days later.
Check your own dates
Enter your exact due date in the conception date calculator to see these results with weekdays and the correct year, or start from your last period with the last-period conception calculator.
Conception Date Calculator: Find the most likely conception date from your due date.
Open the calculatorThis article is general information, not medical advice. Talk to a doctor or midwife about your own pregnancy or fertility.