Could my due date be wrong?

[SanDiegoSunshine]

Throwing this out there for some advice….

I’m 29+2 with first baby. Fell pregnant extremely quickly and it came as a bit of a shock. I’d been on the pill for around 6 months but the pill has never agreed with me tbh. It used to mess with my emotions and I was all over the place. Tried a few diff ones but it’s always been the same. Anyway, discussed with my partner and as we wanted to TTC anyway I stopped taking it. I went cold turkey and waited ages for withdrawal bleed which happened on 8th April. Found out I was pregnant on 12th May.

For all purposes 8/4/21 has always been my considered ‘date of last period’ however a withdrawal bleed isn’t really a period and there was no way of really knowing when I was ovulating as my body was yet to fall back into a natural pattern.

Was given a DD of 10th January but I just ‘feel’ I’m further along. My bump is small so was sent for a growth scan which actually showed the opposite, baby big and over 90th centile at 3lbs already, head is down. Gestational diabetes was negative so ruled out being bigger for that reason. My partner and I aren’t big at all and history of big babies in the family.

I know growth scans have a reputation for being wrong many times however could I actually be due sooner than I’ve been led to believe?

• no history! Sorry typo

Was your due date not based on measurements at 12 week scan?

Scans are only estimated though and usually wrong.

They estimated my son to be 11lb he was 8lb. I wouldn't imagine your dates are wrong if they are only by a few weeks or so or else it would of been obvious at the 12 week scan.

The dating scan you have at around 12 weeks is very accurate as far as I know

The measurements tey take at the 12 week scan are what determines your due date. If you think that its wrong, discuss it with your midwife.

So you think you are due earlier?

Your due date would have been adjusted at your 12-week scan, which is the most accurate way to date a pregnancy. Most accurate however doesn't mean 100% correct to the day. Few things in nature are that precise. Also the duration of a pregnancy can vary from woman to woman, and pregnancy to pregnancy. Some babies are ready at 38 weeks, others wait until 42 weeks, and this is all within normal variation.

My due date was brought forward at 12 weeks but only by 3 days.

I just figured that if growth scans are notoriously wrong could that scan also have dated it wrong?

But a 12 week scan isn't a true 'growth scan'. Its a viability and dating scan. 3 days is a very small difference too.

Dating scans are generally very accurate. Growth scans have a area of error in terms of the baby’s weight but they average out at being correct (although you will only usually hear about the babies where the scans were wrong).

I had DD with no periods so they had to go by scan.

I had a private scan that gave me x date.
NHS dated her as being due x - 1 week date.

She actually came out on x date and one week overdue by NHS records.

My understanding is that the 12-week dating scan is pretty accurate because they are based on very specific measurements of different parts of the embryo. Whereas growth scans later in pregnancy are notoriously wrong because they try to estimate the baby's weight, which is a much less exact science.