It's possible that the sperm hung out in your fallopian tube for a few days until your egg came along, at which point it fertilized the egg and your baby was conceived.
So without knowing the day of conception, how does anyone determine a due date? The method typically used by healthcare providers is simply to count from the first day of your last period.
In fact, when a woman who has very regular, "textbook" 28 day cycles presents for prenatal care, this often turns out to be the correct EDC more often than not.
Other information used to calculate the gestational age, or the number of weeks and days from the first day of the last menstrual period (LMP), includes the size of the uterus on pelvic bimanual examination.
However, it is extremely common to encounter patients who have irregular or infrequent menstrual cycles, or have fibroid tumors that cause their uterus to feel enlarged on pelvic exam, or who conceive shortly after a pregnancy ends (without ever actually having had a period after the last pregnancy), or who got pregnant while taking birth control pills, and these situations often render the above methods useless and misleading when trying to figure out a reliable EDC.
This is where our wonderful ultrasound machines can make a crucial difference.
The results you receive from this tool are for informational purposes only and should not be the basis of your medical decision making.
Consult your physician to determine the medical implications of any tests you take.Creating an NHS Choices account will also allow you to write and save your birth plan online.Human gestation is the same for everyone: It takes about 38 weeks from the day of conception to the day you deliver.Determining the Date of Conception Because the human egg is capable of fertilization for only 12 to 24 hours after ovulation the date of ovulation may be taken as being the date of conception. However, ultrasound determination of the date of ovulation has the same imprecision as does the ultrasound estimate of the gestational age and, therefore, a precise date of conception cannot usually be determined as with in vitro fertilization. With today's modern equipment, we can obtain very reliable images and measurements of even very early pregnancies, sometimes even seeing a heartbeat as early as 5-6 weeks!