QuestionI'm sure this is a strange question. I was using ovulation test to get pregnant. I stopped my birth control and used the OPK's for 2 months. They were positive exactly 2 weeks after my LMP. My cycles were exactly 28 days, but I never got pregnant. on the 3rd month the OPK showed my LH a day early. 2 weeks later (about 3 days before my period was due) I tested positive for being pregnant. I thought I had it all figured out, however, at 17 weeks, my doctor did an ultra sound and siad I was actually 18 weeks pregnant. How can that be? I read somewhere that pregnancy could affect an OPK, but could an OPK show positive for LH surge if I was already a few days pregnant? Or is my docotor wrong by saying I'm 18 weeks when I'm sure I'm only 17 weeks?
AnswerDear Brianna,
I'm wondering if you happened to have had an earlier ultrasound? The reason is that ultrasounds done before 12 weeks are typically the most accurate for dating a pregnancy. Now, ultrasounds done up to 20 weeks are still pretty accurate for dating, but accuracy is definitely increased the earlier they are done. This is because as the pregnancy progresses into the 2nd trimester, each individual fetus may grow/develop at different rates dependent upon a number of factors (mother's health and diet, etc,...). So, if you did actually have an earlier ultrasound that confirmed your calculations, I would personally stick with that original date - or at least keep it in the back of my mind when delivery time gets closer. :-)
OPK's detect LH (luteinizing hormone) which is the hormone associated with ovulation. Pregnancy tests detect hCG, the hormone associated with pregnancy. LH and hCG are, at a molecular level, nearly identical except hCG has a little beta subunit. An OPK tests only for the part of the molecule that LH and hCG have in common. So an OPK will turn positive when it detects either of the "identical twins" - ovulation or pregnancy hormone. The reverse is not true, however, because an HPT tests for the part of the molecule that is unique to hCG. So - when you got a positive reading on the OPK, it may have been picking up hCG and this would make your due date earlier than you probably anticipated. However, please know that there does tend to be quite a few false positives on OPKs.
SO, here's the thing... you got pregnant!!! :-) And less than 5% of babies are actually born on their due date. Babies come when they are good and ready. So you will need to be prepared to go to the hospital a few weeks ahead of time anyway.
I hope this information has helped you and answered your question. I wish you well.
Brenda
