Posted by: Kirst | 2006/11/08

19 wks preg but baby is 18wks GA how??

Hi there, I'm confused about my baby's gestational age, according to my LMP, I'm 19 weeks pregnant on Thursday but the ultrasound I had on Mon. 6 Nov said my baby is measuring 18wks gestational, how the hell can that be? Should my baby not be somewhere round 17 weeks? Does this mean I'm gonna have a huge baby that nappies won't even fit on?

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Our expert says:
Expert ImageGynaeDoc

If you are 19 weeks on Thursday then you were 18 weeks and 4 days on November 6th. The ultrasound is only accurate to within 3-4 days.

Best wishes

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Our users say:
Posted by: Purple | 2006/11/09

A pregnancy is dated from the first day of your last period.

For the first few days of your pregnancy, you are having a period and not actually pregnant. After 14 days plus minus, you ovulate and conception occurs - this is around 2 weeks pregnant.
You miss your period at 4 weeks pregnant. Most people do a pregnancy test a week after they miss their period, so discover they're pregnant at about 5 weeks give or take a few days.

You are pregnant for between 38 and 42 weeks in a full term pregnancy.

Reply to Purple
Posted by: Merraai | 2006/11/09

The dates and rates they give are all just estimates, My baby was all the time 2 weeks ahead of her time on the scans and she was normal (no giant born) so do not worry . If however you are still concerned ask your Dr to explain what is going on.

Reply to Merraai
Posted by: Jessie | 2006/11/08

And no Kirst, it doesn't mean you'll have an enormous baby, it just meant that you maybe ovulated earlier, which is what happened with me :)

Reply to Jessie
Posted by: Jessie | 2006/11/08

Hi Kirst

I think what could be confusing you (as it is me) is that some practitioners work out your pregnancy from your last period, whereas you only concieved a week or 2 later (my case it's a week later), so I'm actually 8 weeks pregnant, but my baby is only 7 weeks.

I don't know if that helps?

Reply to Jessie
Posted by: Purple | 2006/11/08

The only accurate date is the date from working out from your last period and your 5 week dating scan.

All other scans estimate a gestational age depending on the size of the baby. Babies obviously differ in size (as people of all ages do). Also, if the gynae is off in his measurement of that leg bone by less than 1mm, that size estimation is incorrect and so will the estimated gestational age.

My gynae told me not to set any store by the estimated due date or gestational age given on the scan.
My scans consistently told me I was a three weeksahead in my pregnancy. My gynae estimated a birth size of 4kg or more. I had a 3.4kg baby at full term (according to the date of my last period)

Reply to Purple
Posted by: ... | 2006/11/08

No it sounds as if your baby is smaller than the 19 wks that you are calculating your pregnancy at. Maybe you conceived later?

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