Dating scan - don't agree with dates

[CaleyThistle]

I had my 12 week dating scan today and they measured baby as being 13 weeks old tomorrow. That would mean ovulation occurred just after I had 4 days of diarrhoea (sorry - tmi!) and I KNOW we didn't DTD. I've noted in my diary I had EWCM that day (Tuesday) but we didn't DTD until the Saturday morning. Anyone else disagree with their ’medical’ due date?

Well the dates are not out by much, it won't really make any difference to anything.

They do vary a bit, as ovulation and date of conception are not necessarily easy to pinpoint (unless you have certain types of fertility treatment).

You can have ewcm for more than one day and you can have sex and get pregnant up to a week later (long living sperm) so there's two options it could have been?

My due date with DS2 was moved forward by 6 days after the dating scan.

It used to be that if the scan showed size to be within 7 days of your EDD from your LMP that they didn't move it.

I knew exactly when he was conceived but they still changed my due date. It just meant they were pushing me for induction earlier. I kept calm, reasoned that DS1 was 7 days late and still went off my original dates. DS2 was born at 40+4 by my dates, 40+10 by theirs and he had loads of vernix on his skin and the placenta was intact and healthy which showed my dates were probably right. A week is not a lot to move it by in the grand scheme of things, but just listen to your body and remember its ultimately your decision whether to induce or not, but take all the risk factors into consideration.

Dating scans aren't actually accurate to the day. I think they are saying that you are 12 weeks 6 days and you think you are 12 weeks 2 days.

If you look at Appendix 1 they use the 50th centile, so a CRL of 64mm to get 12+6. But if your baby is a bit bigger for gestation - the 95th centile for size or 5th for age - then you come out at 12+1. At 64mm you could be between 12+1 and 13+3 and actually 10% will fall outside those dates.

I'm amazed that there is a faith like belief in scanning dates, given the range for any given fetus size and particularly if you know your dates.

They moved both my childrens dates I know when we dtd with ds as partner was too drunk on new years eve so it was new years day so his dates were 10 days out he was a huge baby long and heavy so understandable, with this one I'm only measuring 5 days behind my thought dates so not too bad! I disagreed totally with son and my midwife told me said shhhhh they are right he was 60cm long when he was born and is still huge

Thanks all. I was just concerned the midwives take it as gospel you are due on xx date and base everything on that. I advised my midwife I didn't have a 28 day cycle for her provisional dating and was brushed off then. As commented, it's only 5 days so I'll not worry about it. (I'm actually hoping bubbs is late as I'm due to attend a 40th birthday party 4 days before her due date!) Eeek!

I've had that with the 28 day cycle thing too.

It does matter - because you might be very strongly encouraged to go for an induction at their dates 40+12 but your dates 40+8. 4 days could make all the difference to avoiding a cascade of intervention.

Thanks all. I was just concerned the midwives take it as gospel you are due on xx date and base everything on that. I advised my midwife I didn't have a 28 day cycle for her provisional dating and was brushed off then. As commented, it's only 5 days so I'll not worry about it. (I'm actually hoping bubbs is late as I'm due to attend a 40th birthday party 4 days before her due date!) Eeek!

It's annoying when you know exactly when you ovulated. I have a short cycle and ovulate early so I told a white lie on my DS and said my last period was earlier than it was so that the dates matched up (he came 3 weeks early anyway so didn't really make a difference in the end)

My estimated dates were 5 days out based on LMP but I know I ovulated on CD 9 rather than 14, so in my head I just carried on my dates. Had my scan on Monday (12+2 their dates, 13 exactly by mine).

LO and behold; 13+2. So if I had gone on lmp there could be a whole weeks difference.

I am sticking with my dates anyway, as I know a new week starts on a Monday and it's a nice day to start! So now I'm 13+2.

It's stupidly over complicated isn't it?

Completely understand. With my last pg, I had a 7 week scan which completely agreed with my dates. However, the 12-week scan, which they insist on using, brought my due date forward.

I had just turned 40 years old & they wanted to induce at 40 weeks, but by my dates I was only 39+2. I refused but agreed to be induced when MY dates said I would be 40 weeks.

Thankfully, spontaneous labour at what they said was 40+4 but what I knew was 39+6.

They moved my due date back by a week and a half at the dating scan, and lo and behold, dd was born a week and a half early (according to the new due date, so bang on mine!)
It really makes no odds though - don't worry.

Oh yes, see that it could make a difference re induction if overdue - sorry.

Thanks for all your feedback. CD1 was 22 April and I have a 34/35 day cycle. I had diarrhea from CD10 to CD14 and I know we didn't DTD until CD19.
I nearly replied that with vomiting and diarrhea there couldn't possibly be any sperm left in my system (!) but I managed to remember basic biology just in time!!

I think your dates look more sensible. While we are taught in school that sperm live for ages (don't get pregnant teenagers). The reality is slightly different. If you look at this chart showing likelihood of conception against day of intercourse, it looks likely that you are right. Also typical luteal phase length of 14 days would give you a day 20 ovulation. You might not be typical.

Dating scans are not 100% accurate. Dd was conceived perfectly as planned on our wedding anniversary. Due date would then be my birthday.

Scan date put her due date 2 weeks before my birthday and she was born by c section at 38 weeks to the medical profession (because of previous com 36 weeks to me.

(Because of previous com

Stupid dog keeps knocking my hand on this phone!

Com

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Fuckin give up!