Accuracy Of U S

8 Replies
Angiconda - June 4

Hey ladies I am wondering if anyone can tell me if and u/s done at 20 weeks is more accurated then 1 done earlier. I am currently 28 weeks by at my 20 week u/s the baby measured a week and a half bigger and by the u/s my EDD would by Aug 24 but my doctor said he would not change it from Sepy 1st. I am wondering which is more accurate (even though I know he will come when he is ready)


Been There - June 4

Probably the earlier one. I have had an u/s every month. My baby keeps having growth spurts. At first he was right on target, then, at 16 weeks, he starting measuring a week ahead in growth. My last one was at 30 weeks and he's measuring 2-3 weeks ahead in growth. So, there is no need to change the due date because it's possible your baby is just a little bigger than expected. That's all.


AngelSummers - June 4

After having my second u/s my baby measured two weeks bigger and my doct. changed my due date.....but he said after my first u/s he thought I was a little farther than it said.


mommie2be - June 4

Usually your ultrasound is more accurate, but doctors like to stick with the EDD from the date of your last period. Mine measured 5 days difference (Aug 6 instead of the 11) and they're currently sticking with Aug 11. I think Drs get concerned when it's an incredible date difference (like two weeks).


Betul - June 4

From what I have heard, if you have an u/s at an early stage (6-10 weeks) it is more accurate for dating than an u/s at a later date. Later babies have growth spurts from week to week and no two babies are the same in measurements.


Jenn2 - June 4

I recently read on a website that if you have an ultrasound before 20 may even have been by 14 weeks or so....that its prediction of due date is usually right within 3 to 5 days. If the Ultrasound is done after 20 weeks it can be a difference of 7 to 10 days from what it estimates.


Roary - June 4

mommie2be: I recently went to my 34 week 5 day ultrasound and most of the baby's measurements were 37 weeks 5 days????... I haven't yet seen my doctor about the ultrasound results. Is this just a normal variation or less common?


mommie2be - June 5

Roary: I think that's normal variation. Especially, like Betul said, in later stages the growth spurts are more frequent and vary mother to mother. Since it's a 3 week difference, your doctor may ask for detailed eating habits (food diary) or any unusual occurences you may've recently experienced during your pregnancy- trying to determine if they need to reevaluate your due date. I'm experiencing that right now too.. I'm measuring 2 weeks ahead and they're having me do a food diary.


Roary - June 5

Mommie2be- thanks for the responds. I am really really not sure about my dates as it is--I didn't get an ultrasound until I was 20+ weeks pregnant and I don't know when my last period was. Hopefully I wont have to keep a food diary--it would bring back too many bad memories and habits. The other thing was that the baby's head was in th 75-80th percentile for a full term infant already. We will just have wait and see I suppose. Thanks again and goodluck to you.



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