U/S or LMP due date?

MrserinJ · January 2013

Hi Everyone,

I had my N/T scan today which went well. I'm wondering if u/a or LMP is more accurate for due date? My LMP puts me at 11w4d and the u/s tech said I was 12w2d and gave me a due date a week earlier. I was charting and using OPK's and got my BFP at 10dpo si not sure how it could be that off? I know it doesn't really make a difference but wondering which one is more accurate? Thanks!

pgermain11 · January 2013

I'm in the same boat though not quite such a difference in time. According to my LMP I'm 11 weeks today, but I know when I triggered and probably ovulated so there is a 3-4 day window of difference. My u/s today showed the baby measuring at 11 weeks 3 days so for my sake I'm going based on that date with my due date being July 28. My doc is going by the July 31st LMP date.

Whatevs. It's all ambiguous. The baby will come when he/she is ready.

fabk · January 2013

I was told by my dr that U/S is most accurate. They changed my date up by a week after my second u/s.

KikiCohen · January 2013

I would personally go by the u/s. That's only a difference of a few days anyway, so I wouldn't worry too much.

MrserinJ · January 2013

Thanks ladies! I guess I'll go by July 22 then, instead of the 29th!

thismplsgirl · January 2013

I'm going by ultrasound date instead of LMP but I wanted to go by the later date since baby will come whenever it comes.

sarbieb · January 2013

I measured 5 days ahead at my 12 wk u/s and the tech said I go by LMP bc the u/s could be off and it gets more and more inaccurate the further along you are. Who knows!

valstulas · January 2013

In the first trimester, ultrasound can diagnose your EDD by plus or minus 3 to 5 days. After the first trimester, it is only accurate to 2 weeks. If you had an earlier dating ultrasound, the EDD you got from that US is more likely to be the accurate one.

Tammyhull82 · January 2013

Lucky my lmp and my u/s are the same this time. It's always different with my last two preg.

meltoine · January 2013

I always suggest people go by their latest date, no matter where it comes from, to push induction talk off as long as possible. In the end, your due date really doesn't matter and the baby will come when s/he is ready. But doctors tend to get induction happy 10 minutes after your due date is passed, even though it means nothing.

valstulas · January 2013

Well, yes and no. I think it depends on your providers. However, the longer you go past your EDD, the more likely your baby will start to experience distress. It is important to have an accurate EDD so that your OB can monitor your baby a little more carefully, starting at 41 weeks routinely, or earlier if indicated. Going well over your EDD, especially without monitoring, can be dangerous.

PackLady82 · January 2013

For me, LMP is a joke, so, I go with the u/s...but if you've been charting and timed your sex to conceive, I'd almost trust that more! At this stage, there is a little variance in baby size, an earlier u/s might be more reliable.

MrserinJ · January 2013

valstulas:
Well, yes and no. I think it depends on your providers. However, the longer you go past your EDD, the more likely your baby will start to experience distress. It is important to have an accurate EDD so that your OB can monitor your baby a little more carefully, starting at 41 weeks routinely, or earlier if indicated. Going well over your EDD, especially without monitoring, can be dangerous.

This is very true! My doctor is very antiintervention, if possible. He has delivered my other 2 sons. My first, my water broke and 20 hours later, I had no contractions. He knew a vaginally birth was important to me so eventually started Pitocin and allowed me to labor for another 20 hours while monitoring me closely. With my second, I was 1.5 weeks over due and he said we wouldn't discuss induction until at least days over. I guess it really depends on your doctor or provider.

pepomntpat · January 2013

I think the u/s tends to be more accurate. But, when I had my first u/s around 7 weeks I was a week behind my O date. The second u/s I was 4 days behind my O date and at the NT scan I was spot on. So, I guess LMP it is this time around. My doctor also wouldn't change the EDD unless the u/s was more than a week off.

PrimRoseMama · January 2013

fabk:
I was told by my dr that U/S is most accurate. They changed my date up by a week after my second u/s.

Yep. Go by gestational age measurements from the ultrasound! LMP is a guess they use in the beginning. U/S tend to be more accurate.

Lisa73101 · January 2013

PrimRoseMama:
fabk:
I was told by my dr that U/S is most accurate. They changed my date up by a week after my second u/s.
Yep. Go by gestational age measurements from the ultrasound! LMP is a guess they use in the beginning. U/S tend to be more accurate.

The early dating U/S is pretty accurate and as you progress further along, those U/Ss are not as accurate. I would use your LMP especially since you were charting and if that matched up closer to your dating U/S. With my first two pregnancies, we used the dating U/S since my cycles were not regular at the time. By the NT and 20 week U/S they measured differently, but we always stuck with the first date and those were pretty accurate. This time I was charting and began testing at 10DPO so I'm pretty certain when I O'ed. I measured 2 days ahead at the dating U/S and then 6 days ahead at the NT scan. We are keeping my original due date based on my LMP though. Like PP said, I think that it's better to go with the latest date to avoid induction talks, if possible.

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