Which would you say is more reliable -- LMP, or ultrasound -- for a due date?

Question

Not that I'm banking on anything happening precisely on schedule...

But: five days (yeah, big deal, but) discrepancy between the date the LMP (which is accurate to within a day) says, and what a 10-week ultrasound says.

Your experiences?

(Got it from a GP I don't really like to rely on anyway; do not see obstetrician for another week and a bit.)

Re. "It's nothing that you should get hung up about" -- indeed. I promise not to be one of those people who comes on here saying "I'm almost 38 weeks -- how can I induce?"

Answer 1

LMP. Ultrasounds can be affected by so many different factors, it's hard to say it's extremely reliable. LMP is a set-in-stone date and calculation.

Answer 2

LMP is really more accurate almost all the time, compared to ultrasound, which can be significantly off and cannot be relied upon to date a pregnancy outside of the first trimester at all -- and you're very nearly there.

But if the difference is 5 days, that's fairly immaterial. Remember that it's an _estimated_ due date, not a deadline upon which your pregnancy can, will or even *should* end. It's a reference point, nothing more. It's nothing that you should get hung up about.

Answer 3

LMP is maximum precise once you've a common 28 day cycle. i'd continually bypass with the estimate that would want to provide the later due date so as that there is a lot less rigidity to set off. you've a midwife, so as that likely is very no longer a huge challenge. First babies have a tendency to take longer, my midwife instructed me that there is a few information to point that first pregnancies very last in the route of 40 2 weeks than 40 weeks that are envisioned. That wasn't genuine for me - both one in all my babies precisely 2 days after their due date. do not get stuck up in the date, only pay interest on your body--you'll favor to for labor.

Answer 4

After 13 weeks an ultrasound can be up to 2 weeks off..usually short of what you really are. So if your periods were regular the LMP would be your best bet..but if your like me my periods wernt regular and my cycles were only 21-24 days each month which throws my due date up a week from my LMP due date. Then When i went for my 20 week U.S they said that my baby only measured that of 19 weeks..but then he said with my irregular period and the measurements of my belly i was actually 21 weeks...so you never really know until the baby gets here. But good luck!!

Answer 5

If you usually have a 28-day cycle, I'd say go by your LMP. Or if you have a longer cycle, count when you should have had your period and then count back 14 days (or use the date of conception if you know it). I did this with my daughter and was only a day or so off from the ultrasound -- but she came 9 days earlier than that, so who knows!

Sorry I'm not more help!

Answer 6

if you are pretty accurate about your period I would say LMP, I didn't get an ultrasound until I was 19 weeks, and I was just guessing on my LMP and I was right on the money, my doctor tried to guess by looking at my stomach and he was wrong. Ultrasounds are not 100 percent accurate.

Answer 7

I'd say ultrasound only because although you know the date of your lmp you don't know if you fell pregnant 5 day's after or 3 weeks after. You'd only be guessing. The ultrasound is set up to measure the babies developing schedule which would be more accurate to the day as to how far your pregnancy is.

Answer 8

LMP. ultra sounds determines the age by the size, what if you were having a small or big baby? they told me my bubs would be around 9 pounds, she was a healthy 7 pound baby, fair enough, i also went 1 week overdue, but that was closer than the ultrasound guess, the ultrasound said i was due 22nd dec, my lmp was 26th dec, i had her 2nd jan, so really, who knows?

Answer 9

My doc said LMP, unless the discrepency is several weeks, or your cyle is very irregular.