Pelvic floor muscle biometry and pelvic organ mobility in East Asian and Caucasian nulliparae

ABSTRACT Objective To compare the differences in levator ani muscle biometry and hiatal dimensions between pregnant nulliparous Caucasian and East Asian women. Methods Offline analysis of three/four‐dimensional ultrasound volume data obtained from two groups of pregnant nulliparous women, Caucasian and East Asian, was performed. Volume acquisition was performed in the late third trimester using the same method in both groups, in the context of two prospective observational studies with identical entry criteria. Pelvic organ descent and levator hiatal dimensions were assessed using the volumes acquired on Valsalva maneuver, and pubovisceral muscle thickness was measured from the volumes obtained on pelvic floor muscle contraction ( PFMC ). Results Datasets of 200 East Asian and 168 Caucasian women were analyzed. Compared with Caucasian women, East Asian women had a significantly lower body mass index. All indices of pelvic organ descent were significantly higher in the Caucasian group than in the East Asian group. The difference, expressed as a percentage, in levator hiatal area on both Valsalva maneuver and PFMC was markedly greater in Caucasian (32% vs 19%; P < 0.001) than in East Asian (24% vs 20%; P = 0.01) women. After controlling for potential confounders using multivariate regression analysis, racial origin remained the only significant factor associated with differences in pelvic organ descent and hiatal dimensions. The thickness and area of pubovisceral muscle were significantly higher in the East Asian group. Conclusions Pregnant women of East Asian racial origin have a thicker pubovisceral muscle, smaller hiatus and less mobility of pelvic organs than do pregnant Caucasian women. Copyright © 2014 ISUOG. Published by John Wiley & Sons Ltd.