To determine the date of conception, use an online ovulation calculator found on WebMD or BabyMed. Alternatively, women can identify the last menstrual period that they have had and add 40 weeks to determine due date, which would make it possible to determine the day of fertilization by calculating 266 days before the due date.
This date is the most likely date of fertilization. For women who know what their ovulating schedule is, it can be much easier to determine the day that they got pregnant. Review the period of ovulation that occurred during the woman's last period, and this is most likely the time that the baby was fertilized, reports BabyMed.
Another opportunity to determine the day of the baby's fertilization is to see when the baby's heart beat is visible on the ultrasound machine. This feat usually occurs at 6 weeks, which means that a woman who can hear the heartbeat of her baby needs only count back 6 weeks to find the exact date, reports BabyMed.
Ovulation is the period of time that happens "around day 14 of a menstrual cycle," writes WebMD, and it typically lasts for 5 to 7 days. Before ovulation begins, most women experience vaginal secretions. The ovulation period will vary from individual to individual, however, but most ovulation cycles follow these rules.