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Pregnancy

Talk about every stage of pregnancy, from early symptoms to preparing for birth.

Original poster

Baby measuring 2.4 weeks ahead at 12 week scan

43 replies

BabyBorn · 02/01/2022 09:50

Hi ladies,

Looking for some insight to help me understand what is going on here.

Since my mid 20’s if I was not on any hormonal contraception, I have always been able to feel the exact time when my body tries to ovulate. Back then it sometimes used to take up-to 3 days for the egg to be released which was really painful. I got pregnant at 26 and knew when I ovulated. Scans put DD2 5 days ahead of my dates. This was fine as it was only 5 days. DD2 was impressively born on the date my husband and I were expecting her, which was 5 days after the EDD the hospital issued. She was born weighing 9lb 1.

In June 2019 I came off my contraception pill as it has never agreed with me and I was getting horrible side effects. I downloaded the Clue App to help me log my cycles. I have been logging my cycles ever since.

Fast forward to now, I am expecting my 3rd baby. Went for an early scan as have had a previous ectopic rupture so wanted to check the pregnancy was in the correct place, which thankfully it was. The sonographer said I was measuring 2.2 weeks ahead of the dates I gave them. I wasn’t overly worried as I just thought that the scan at that stage of pregnancy might not be that accurate and the dates would balance out at our 12 week scan.

Went to our 12 week scan last Wednesday and sonographer has put us 2.4 weeks ahead. I told her I was only just 11 weeks on that day according to my dates. I explained that I had gone from the date I had my ovulation pain and the date was exact. We had DTD 3 days before so the sperm would have already been waiting for the egg to be released. After this scan I was given the sonographers paperwork and my pregnancy notes and given a slip to give to the midwife who I had to see after the scan that said “please take your notes to the midwives office for a growth scan to be created”. Midwife have me a growth chart that showed my DD’s birth weight and showed she was on the 94th centile for her birth weight. She then explained that this time they wanted me to do the Glucose test to check for Gestational diabetes! She was 9.1 not over 10lbs which the NHS state the minimum size is before you are offered the Glucose testing.

I totally understand the fact that all babies are different sizes and that scans are based on average sizes at that point in pregnancy and are not 100% accurate but I have never had such a big indifference with dates like this before.

I feel that my dates are correct but wondering how both scans could be so out? The scans were 3.5 weeks apart. Can anyone shed any light on this at all?

OP posts:
GinnyBee · 02/01/2022 10:11

I'm measuring a week ahead of my dates, which isn't as much as yours but I know when I ovulated, I know when we had sex, and I also tested 5 days before my expected period (dpo8) so in reality it's impossible that we would have conceived a week ahead. A day or two maybe, but not a whole week. I've had 5 scans so far in this pregnancy due to previous losses - 3 early reassurance scans with the EPU, standard 12 week scan, private gender scan at 17 weeks and standard 20 week scan on Friday. At the earlier scans he had raced ahead by a couple extra days for each scan - at 6 weeks measuring bang on, 8 weeks he was 2 days ahead, 10 weeks he was 4 days ahead, 12 weeks 5 days ahead and 17 weeks a full week ahead. At my 20 week scan he's still only 1 week ahead so seems to have settled. I think I'm just going to have a tall baby!

If your midwife doesn't seem concerned then try to relax :) And there are many reasons why you may be referred for the glucose test, it's good that they're doing it if you're concerned about this baby's fast growth even if your previous one wasn't "big enough".

Lazypuppy · 02/01/2022 10:12

I thought they always added 2 weeks on, so basically from LMP, so when you get your positive pregnancy test you are already 3/4 weeks pregnant. As everyone ovulates at different points in their cycle

Moancup · 02/01/2022 10:12

Are you dating from your (guessed) day of ovulation rather than last period?

Your first baby sounds like she was overdue and carried on gaining weight in utero.

BernadetteRostankowskiWolowitz · 02/01/2022 10:18

I get ovulation pain too, so knew the exact date I ovulated for both my pregnancies

To get the edd you can either add 38 weeks Onto ovulation day or go a fortnight earlier and take the 40 weeks.

Original poster
BabyBorn · 02/01/2022 10:19

@Lazypuppy they measured the baby to come up with these sizes. I went from my actual ovulation date and didn’t add the two weeks on top of it as there was no point as I know when it happened x

OP posts:
Original poster
BabyBorn · 02/01/2022 10:21

@Moancup it’s not guessed ovulation. It was when I ovulated.

She was not overdue. She was bang on my dates. My first DD was larger than expected too but not as big, but I didn’t know when I ovulated when I had my first 17 years ago.

OP posts:
Moancup · 02/01/2022 10:22

You do need to add the extra two weeks as otherwise you are speaking a different language to your doctors. Confused Pregnancies are measured from last period not date of conception. Any discussion about what’s normal at five week, 12 weeks etc means X weeks from last period.

WinterSpringSummerorFall · 02/01/2022 10:24

[quote BabyBorn]@Lazypuppy they measured the baby to come up with these sizes. I went from my actual ovulation date and didn’t add the two weeks on top of it as there was no point as I know when it happened x[/quote]
I think this might be the issue. When you ovulate you are already 2 weeks pregnant by how they do the dating...

OakRowan · 02/01/2022 10:24

You might know exactly when you ovulate but you can't know when you conceived. I measured a few weeks ahead at that scan, puts me at getting pregnant before I even ovulated, but I just shrugged it off. So long as you and baby are OK, due dates aren't exact are they.

Original poster
BabyBorn · 02/01/2022 10:27

@GinnyBee wow! You’ve had a lot of scans! 😆 glad they are keeping an eye on you though! I did read that scans could be as little as 5 days out upto 1.2 weeks out, so you are in that time frame which is good. I don’t understand how mine can be that far out. They went by babies measurements at the ultrasound scan. The sonographer even checked twice.

They didn’t do the glucose testing on me 20 years ago when I had my second. Really confusing but yes you are right, at least they are monitoring things x

OP posts:
GinnyBee · 02/01/2022 10:28

Ah, that explains it. Pregnancies are dated 40 weeks from first day of last period or 38 weeks from ovulation. So when you ovulate you're already 2 weeks pregnant.

Original poster
BabyBorn · 02/01/2022 10:29

@WinterSpringSummerorFall the sonographer measured the fetus that’s how she came up with the date. She even checked it twice.

OP posts:
MadeForThis · 02/01/2022 10:30

The scan is dated from the date of your last period. The midwives know you weren't pregnant then and hadn't ovulated. That's just the standard measurement.

You need to add the two weeks on. Just so you are using the same scale as them.

MabelG · 02/01/2022 10:30

Pregnancy is dated from the first day of your period, not ovulation, which will account for the two weeks. I had IVF so know the exact date and even the time the embryo was put back however they still added two weeks on.

WinterSpringSummerorFall · 02/01/2022 10:31

OP, can you acknowledge the 2 weeks difference point?

when did you ovulate?
when was your last period?
what do you think your dates are?

Mumsnet will tell you how pregnant you are.Grin

Lazypuppy · 02/01/2022 10:31

OP you say sonographer said you were 2.4 weeks ahead of your date, which is correct as they will have added on the extra 2 weeks, they are working on a 40 week pregnancy from LMP,you are doing it as 38 week pregnancy from ovulation. You'reboth speaking a different language

Original poster
BabyBorn · 02/01/2022 10:33

@Moancup I have already explained that the sonographer got these dates from the measurements of the baby at the scan which she checked twice.

If the hospitals dates were to be correct it means I was pregnant 5 days before my LMP which is impossible.

OP posts:
Lazypuppy · 02/01/2022 10:34

Thats how the dates woek OP! Every woman is classed as pregnant before she is

Lazypuppy · 02/01/2022 10:36

I ovulated 3 weeks ago, but i am classed as being 5 weeks pregnant

Totalwasteofpaper · 02/01/2022 10:36

The day you conceive is considered 2 weeks pregnant.

Have you taken the glucose test? If not you really should.

Original poster
BabyBorn · 02/01/2022 10:37

@WinterSpringSummerorFall

LMP was 1st of October
DTD 10th of October
I ovulated on the 13th of October
Implantation spotting 26th and 27th of October.

OP posts:
DarlingDarwin · 02/01/2022 10:37

It sounds like they were 5 days out OP. Like others have said, they will tell you how many weeks pregnant you are from your last period. So they take the measurement, work out how big the baby is, then bang on 2 weeks to tell you your official pregnancy weeks

Original poster
BabyBorn · 02/01/2022 10:38

@Totalwasteofpaper not taken the glucose test yet as isn’t done until week 16.

OP posts:
GinnyBee · 02/01/2022 10:39

@BabyBorn that 5 days is normal variation. If the sonographer dated you as 13 weeks gestation at the scan that means you would have conceived 11 weeks ago. That’s just how it works! 5 days difference is normal as the measurements are estimates and babies grow at different rates.

Lazypuppy · 02/01/2022 10:39

So from LMP you are around 13 weeks pregnant, which is what sonographer is telling you