U/S for due dates

[Banana731]

My sister found out that she was pregnant. She believes that she conceived between the 15th and 29th of July, but she does not have regular menstrual cycles, and has no way of using that as an indicator.

What is the upper limit for u/s to be accurate in determining a due date? It's important that she get an accurate one, because she's crazy and wants to schedule a c/s. I'm working on convincing her that it's not a good idea, but her 1st dd was overdue and had some serious problems as a result(she had the same problem with the EDD last time.) I think a solid due date would help put her at ease.

TIA

[MsBlack]

The earlier the u/s, the more accurate it can be in determining gestational age. I wouldn't say it gets more accurate in determining 'due date', since that can vary on average by about 4 weeks from woman to woman. But before 13 weeks gestation or so, u/s can be accurate on gestational age with a 5 day variance. The later the u/s, the less accurate the measure of gestational age--after mid pregnancy, the margin for u/s error goes up to about 2weeks in either direction.

Does she know that a woman is 3times more likely to die as a result of csec than vaginal birth? Does she know that the rate of complications for babies is also much higher for csec babies? Perhaps if she did, she would be less urgent about scheduling her surgery...

[SublimeBirthGirl]

I think 18 weeks and beyond is when it become smore of a crapshoot. Also, different babies take different lengths of time to grow. I was SURE of conception with both babies and both came beyond 40 weeks (my 1st 11 days, my 2nd 6 days). Show her this c-section fact sheet:

http://www.motherfriendly.org/Downlo...fact-sheet.pdf

[Banana731]

Thanks guys, like I said, I 'm working on her. She was told here placenta had begun breaking down with her first(after the c/s), and I know that she's worried about that. I am trying to help understand that every pregnancy is different, but she's just one of those people. I have the rest of her pregnancy to work on her though, so I'm hopeful!

[applejuice]

U/S scans are accurate as far as size and due dates are concerned up to the twentieth week.

After that point, heredity takes over as far as size, weight, and bone density and you have to look to your ancestors for verification.