Pregnancy due date based on ultrasound dating lots of fish dating service
If your menstruation cycle is not regular, say you only get your period every 6 or 7 weeks, then you may find this calculation more suitable.
Ultrasound uses the size of the fetus to determine the gestational age (the time elapsed since the the first day of the last menstrual period).
But in more than 90 out of 100 women who are overdue, contractions start on their own within two weeks of their due date.
The reason why the baby is overdue is usually not known.
I went today for an ultrasound and they said I'm 4 and 1/2 to 5 weeks pregnant. I think I'm 3 weeks and 2 days pregnant - that seems logical to me. Your due date is based on your last menstrual period, so that would put it about two weeks off from your conception date. You are very logical, however, 2 weeks are added to the actual date that you got pregnant.
While pregnancy is actually 9 1/2 months, doctors calculate it as 10 months because they add those two weeks in before conception. It has something to do with the weeks until you missed period from your last period.
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.