QuestionThe doctors say that my due date is March 15,2007 so when would I have gotten pregnant with my child? The doctor told me about June 28, 2006 but that doesn't equal out 40 weeks so that confused me a little. This is my first child so I am just curious. Any information will be helpful. Thanks!!
Brandi
AnswerCalculating due dates is a tricky business, and of course any date you get is completely arbitrary; the baby is not going to get the memo!
The classic method of calculating due dates uses the date of your last menstrual period (LMP). This method assumes a cycle length of 28 days, with ovulation on day 14. You take your LMP, add 7 days, subtract 3 months, then add one year. To get a date of 3/15/2007, you would have started with an LMP of 6/08/2006. Because you are assuming ovulation on day 14, that would be a conception date of 6/22/2006.
Naturally, most women do not have clockwork cycles of 28 days, with ovulation on day 14. In fact, most women are not even regular at all! Women can have a range of cycle lengths, anywhere from 21 to 50 days or more. Ovulation can occur anywhere from 10 to 18 days before the next period, or on cycle days 3 to 40! So by using the classic method, doctors can come up with due dates that will obviously be quite wrong!
Now, in your case, did your doctor do an early ultrasound, during your first trimester? If so, these early ultrasounds are very good at pinpointing the age of the fetus, sometimes to the day. He may have gotten an fetal age at that time that showed you conceived on 6/28/2006. However, he is simply continuing to use your LMP to calculate your due date of 3/15/2007. No, this doesn't make sense, it's simply habit on the doctor's part. If this is what is happening in your case, you should ask the doctor to correct your due date to 3/21/2007. This will prevent him from pressuring you into an induction or c-section before your baby is ready to be born.
Apart from early, first-trimester ultrasounds, the only other way to determine an accurate date of conception is if the mother is using BBT (basal body temperature) charting when she conceives. This will allow her to see her ovulation date on the chart, pinpointing conception and allowing an accurate due date calculation. I use this method myself, as I am one of those women with 35-50-day cycles who really needs the adjusted due date.
One final possible explanation for the altered date is implantation. Implantation usually occurs around 7 days after fertilization of the egg. Perhaps your doctor has given you this possible date as a conception date.
Congratulations on your pregnancy!
