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Lmp and ultrasound dates not matching – what to expect general message board, forums, what to expect

LMP and Ultrasound dates not matching

Ok, so this is my first post ever and I hope I am posting in the right place. To give a little background this is my third pregnancy. My first was an oops, the second is with my now husband (different father from my first) and we had trouble conceiving him due to low sperm morphology. With this one we had been trying about 10 months only and were pleasantly surprised to find out we were expecting again so soon. I am still nursing and I know my cycles have not been perfect since they have returned after my last. Because of this I have been charting and using OPK’s to determine and confirm ovulation. So the cycle in which we got pregnant according to my OPK’s and chart I should have ovulated on CD 16. I had some slight brown spotting around the day I should have started my period (11dpo) and then on 13dpo is when I got my BFP. Also, around 8dpo I had what felt like ovulation pains again but I had already ovulated and figured it was possible implantation pains? OK, so fast forward to this past week. I went in to have an early U/S figuring I was around 6w2d or so according to my LMP but also knowing I could date a bit off of that due to my later ovulation. Well when they did the U/S all we saw was the gestational sac, no yolk sac or fetal pole. The doctor who read my scans dated me based on the size of the gestational sac at 4w4d. I am concerned something is wrong and baby has stopped developing. No one else seems concerned at all and keeps telling me I have my dates wrong and that its just too early to see anything and that I must have ovulated later than I thought. I asked the doctor about my chart and he said he didn’t care about that stuff and that I ovulated late (kind of frustrating). He also said that based on when I had possible implantation spotting around the time of my expected period that my dates line up with the scan. This would only make sense if they were not including the two weeks prior to ovulation. I go in another three weeks for my first OB appt. and I thought I would be around 9w or so then but now it seems I will be closer to 7.5. they said I can have another U/S at that time to check on things. They say everything looks great right now but I just feel like something is not right. How can my dates be THAT off when I was so diligent about tracking everything? Would late implantation throw things off that much? Could I have potentially ovulated at the 8 days past what I thought was ovulation? Should I just prepare for the worst or is there hope that everything is totally OK? I am just so confused. with my first two pregnancies my LMP and U/S always matched up very closely. Please let me know what you think, good or bad. I just wish I could figure this out! Thank you so much in advance!

To be 100% honest with you, I think it really could go either way. I have had 2 really early miscarriages, and they are very common. As you say, it is possible that you are experiencing an early miscarriage where you are still registering HCG levels but the pregnancy is not developing with a yolk sac and fetal pole (a blighted ovum). I think it’s also possible you ovulated later than you thought you did, especially since your cycles aren’t totally regular, like you said. I know how frustrating it is to have to wait these 3 weeks. If you really want, you can try to monitor yourself with home pregnancy tests, but you may drive yourself crazy trying to analyze lines and such. When I had my earliest miscarriage, the line eventually faded away to a negative test over a period of a week or two.

I hope it’s all good news for you and best of luck!

Thank you for being honest with me!! I guess I wouldn’t be concerned if I had not been so diligent at tracking my ovulation and had no clue when I had ovulated. I guess in my mind I am already preparing for the worst 🙁 it just stinks not knowing if/when we will get pregnant again. I do keep taking pregnancy tests and from when I first found out they kept getting darker and darker. I took another one yesterday and it was darker than the control line but I also know that sometimes your body won’t recognize the loss for a while and will continue to try and support the pregnancy. My sister had a miscarriage and she said her tests were still dark positive for a while even after she had miscarried.

Maybe you really did ovulate later and then implant later than you thought. Later ovulation/implantation can make a difference and I’ve seen it happen plenty of times (I’m a nurse). With my last pregnancy I went to the doctor thinking I was 8w2d and when the tech did my ultrasound it showed me to be approximately 6w2d about two weeks off. All we saw was a sac, I was told to wait another two weeks and have a repeat ultrasound. Two weeks later there was his little heart flickering, he’s now almost two. I would take it one day at a time and go with what your doctors are saying until proven otherwise. I’m sure it must be frustrating, hang in there.

That is so encouraging to hear! Thank you so much for replying! I feel like a crazy person. With having struggled with infertility issues I have come to know my body so well and maybe it is just throwing me for a loop this time 🙂 three weeks is going to be a long time to wait before I have another ultrasound but hopefully it will give the little bean some time to grow and make him/herself visible for the next scan.

Thank god my doctor wasnt stupid. Mine also didnt count the two weeks between lmp and ovulation. My due date was 40 weeks from the day i ovulated. And i got induced a week late and she was small. So it would have been a nicu stay if she was born two weeks earlier.

I don’t think it means a doctor is “stupid” because he/she calculates your due date as 40 weeks from LMP. That is standard practice and works out for most babies. It is less accurate if your period is not regular, in which case early ultrasound dating can be more reliable.

Yes it is stupid. NO ONE is pregnant for two weeks out of every month. im glad some are moving away from it.

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