Does due date change at 20 week scan?

[groundskeeper]

My due date based on my LMP exactly matched by due date from my dating scan at 13+6 weeks. My maternity pay is calculated using the pay I receive from 18-25 weeks so I have been booking some extra work to align with those dates to boost my maternity pay. My anomaly scan is next week on 19+6. I’m wondering how likely it is that the date will change at that scan? My understanding is first trimester ultrasound is much more accurate for due date? I’m in the U.K. if that changes anything.

 

[eline]

@groundskeeper It’s unlikely the due date will change but it’s also very unlikely you’ll give birth on your actual due date. I think something like 30% of women do and that’s it.

 

[groundskeeper]

@eline Thanks, I am not concerned about giving birth on my actual due date as I know that’s an estimate, more wanted to know if the date might change still as my maternity pay will be calculated based on my earnings between weeks 18-25 of my pregnancy so if the due date changes at my 20 week scan, they’ll use that date to calculate what weeks 18-25 would actually be and it might affect the amount of maternity pay I get based on the income I’ve received in those weeks, even though I’ve been going off current dates

 

[vido]

@groundskeeper I was measuring more than a week ahead at the anatomy scan, and they didn't change the due date. Babies vary in size at this stage. The dating is only accurate for the early ultrasounds.

 

[eline]

@groundskeeper I believe baby has to measure 6 days or more ahead/behind for them to change your due date. So, more than likely, the date you’re using for leave should be fine

 

[shantom]

@groundskeeper I was due May 4, at my 20 week scan they changed it to May 10, I gave birth on April 29. Your date might change and it also might not really mean anything

 

[shak4969]

@groundskeeper Mine changed to a week earlier. That being said, I had been measuring a week ahead for most of my pregnancy so they said they’d shift it up if I was still measuring ahead by the anatomy scan. I’m now waiting for baby to come, past my due date lol

 

[fhaoipteh]

@groundskeeper In the UK, too! In my experience, your job/payroll/HR will most likely go off of the due date on the MATB1 form to calculate your qualifying week so that theoretically could mean that your date could be changed before you receive the actual MATB1? However, I don’t have direct experience with this so OP, this might be worth posting in r/PregnancyUK as someone will likely have experience with dates being changed before or after receiving their MATB1 that can help!

 

[groundskeeper]

@fhaoipteh Thank you

 

[noracharlesfan]

@groundskeeper Mine changed at my 12 week scan because I was actually 11 weeks at the time.

 

[decrypted]

@groundskeeper https://evidencebasedbirth.com/evidence-on-due-dates/

Whether they change your due date or not is going to partially depend on practice and partially depend on how different baby is measuring at 20 weeks vs your dating scan.

 

[terrystrickl]

@groundskeeper When I get ultrasounds it has a few due dates listed on it. Due date based on self reporting (lmp usually but for me, Ivf transfer), due date based on initial clinic scan, due date based on ultrasound that day. They’re all kind of different. Like my due date based on my Ivf transfer is 2/25 but my 28 week ultrasound growth had him at 2/15. I don’t think they’ve “changed” my due date. Just seems like he is measuring ahead.

 

[christopher333]

@groundskeeper As some have indicated it seems it varies by practice but in my own experience (US) my baby is measuring a week behind 31st percentile and my doctors said they wouldn't think to change my due date unless she starts measuring 2 weeks behind or under the 10th percentile.

 

[nataliya]

@groundskeeper I think this will really depend on your doctor. I measured more than a week ahead at mine and the date was not changed. My office doesn’t change them without significant compelling evidence the original was wrong.

 

[groundskeeper]

I just wanted to clarify I am an FTM. And that in the U.K. after the 20 week scan you get issued with a MATB1 form to give to your employer with the EDD for them to use to work out your maternity pay. Therefore wasn‘t sure if they change the dates at 20 week scan or more often than not use the dating scan date.

 

[kidkaos2]

@groundskeeper I don’t think they’ll change your due date at that point

 

[katrina2017]

@groundskeeper No. Dating scan earlier in pregnancy is most accurate.