Implantation bleeding and due date?

Question

I went off the pill in July and waited until Dec to start trying for pregnancy. I had sex on Dec 18th and on Dec 31st I got a very light bleed (1-2 days). I had sex again in Jan. (10 and 12 days from my bleed in Dec) since I was trying. I got a positive result for a pregnancy test at the end of Jan. I’m trying to figure out how to tell if December’s bleed was an implantation bleed or a normal period. Would the implantation in the lining of the uterus throw off an ultrasound at 6 weeks to push my due date back 3-4 weeks?

Answer

Last Updated: July 22, 2013
Congratulations on your pregnancy! Also on the wisdom of waiting the several months to achieve a pregnancy after taking birth control pills. The most common and the most often used method of dating pregnancy is the gestational age, which is measured from the first day of the last menstrual period. In this way pregnancy is 40 weeks in duration instead of of the actual 38 weeks.

The other way of measuring the date is the fetal age measured from the estimated time of conception. Measuring this way it will be 38 weeks.

The third, and now becoming the standard of practice, is early ultra sound done in the first trimester of pregnancy. This dating is done by measurement of the crown-rump length of the fetus. This is thought to be accurate within plus or minus 3 days. In your case this may not have been done and your pregnancy is measured from the Dec. 31 bleed, which may have been an implantation bleed. Implantation bleeding or mucus usually occurs seven to nine days after conception. Unless measurement is done the ultrasound dates from the last menstrual period. You could ask to have this measurement done by your MD.

After the birth of your baby we encourage all mothers to breastfeed and use a natural method of fertility awareness which is better for mother and baby.

Good luck to you.

Theresa Mitchell

Answered By:

Theresa Mitchell, RN
Theresa Mitchell, RN, taught the Creighton Model FertilityCare System in the Oakland region.

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