SONOGRAPHIC ASSESSMENT OF BIRTH-WEIGHT AMONG BREECH PRESENTATIONS

The objective of this study was to determine whether there was a diffe rence in the accuracy of sonographically determined birth weight estim ate in fetuses presenting by the breech as compared to the vertex.. Pr ospectively, 104 consecutive singleton fetuses presented by the breech presentation were identified who also had a sonographic estimate of b irth weight within 72 h of delivery. The control group (n = 104) consi sted of fetuses presenting by the vertex of women who had the followin g hospital number and who were of similar demographic characteristics; the birth weight estimate in the control group had to be within 100 g of that of the women with the breech fetus. Tire estimate of the birt h weight was derived for both groups using seven published models. Pre diction limits were calculated for an estimated vs. actual birth weigh t for parturients with breech presentation. Among the study group, the mean standardized absolute error was similar for the seven models (ra nge 120 +/- 104 to 138 +/- 118 g/kg; p = 0.08). For six of the models, the mean standardized absolute error was significantly higher for fet uses in the breech presentation than for fetuses in vertex presentatio n (range 80 +/- 63 to 112 +/- 95 g/kg; p = 0.02 to < 0.0001). Predicti on limit calculations indicate that 99% of the time the actual birth w eight was between 1500 and 3999 g if the estimate of birth weight was 2400-2900 g. We conclude that, for fetuses in a breech presentation, t he error with most models is significantly higher than for a singleton in the vertex position.