Dating for conception
Dating a pregnancy can cause confusion, because it can be done in either of two different ways.
Pregnancy can be dated from the first day of the last menstrual period or it can be dated from the day of ovulation.
No one understood that ovulation was required for conception or when ovulation occurred.
Obviously, you aren’t pregnant until conception occurs. In many other places, the new knowledge has been incorporated into a dating system that starts with conception."Ultrasound measurement of the embryo or fetus in the first trimester (up to and including 13 6/7 weeks of gestation) is the most accurate method to establish or confirm gestational age" . This free online conception calculator will determine the conception date -- including the day of the week -- based on the selected month, day, and year of your pregnancy due date. If you have a 28-day menstrual cycle — which is assumed by many healthcare providers — you most likely ovulated on day 14.If your cycle is a few days longer, you probably ovulated after day 14, and your baby may arrive a few days after your estimated due date.