This is a question from a woman on a list I am on:

"My midwife suggested I get an ultrasound to determine the thickness of my uterus near the scar because women with a thickness of greater than 3.5 mm are less likely to rupture and having a thickness of 2mm or less puts a woman at greater risk.


The statistics my midwife gave me were very clear about things like ruptures vs. slight tears, and natural birth, not including inductions, etc. They were pretty thorough statistics, for the most part, but not a lot on how valid the ultrasound would be for me."

Do you have more info about this Henci? Thanks.

I don't have anything recent on this issue, but here is the gist of the discussion taken from:

Lieberman E. Risk factors for uterine rupture during a trial of labor after cesarean. Clin Obstet Gynecol 2001;44(3):609-21.

This review is discussing a study (Rozenberg P, Goffinet F, PHillippe HG, et al. Ultrasonographic measurement of lower uterine segment to assess risk of defects of scarred uterus. Lancet 1996;347:281-4.) in which thickness of the uterine scar in late pregnancy was correlated with likelihood of scar rupture. The reviewer notes that using a cut-off of 2.5 mm or less would be a reasonable threshold in that only 8% of the study population had a scar thickness this thin and 10% of them experienced a scar rupture. However, the reviewer also notes that the overall scar rupture rate in the study population was 2.3%. That tells you that the results of this study cannot be generalized to a population that received proper care because any number of VBAC studies have reported scar rupture rates of 0.5% or less.

If you follow the link for Rozenberg to the PubMed site, you will be able to use the "related articles" function to see other, more recent research on this issue. 

-- Henci  

Thank you.

What about the accuracy of ultra sound in determining the thickness of the uterus?  How accurate can it be?
And don't women in general have thinner and thicker areas in the uterus?

Thanks.
maria.

Those are all good questions to which I don't know the answers. I expect it would be more accurate than amniotic fluid volume estimates because it's a much more straightforward measurement. The studies themselves might give information.

-- Henci