The relation between fetal abdominal circumference and menstrual cycle age was determined by cross-sectional analysis of 400 fetuses (15-41 weeks) examined with a linear-array real-time ultrasound scanner using specifically defined methodology. Mathematical modeling of the data demonstrated that the liner quadratic function was an optimal model (r2 = 97.9%). Predicted abdominal circumference values at specific points in gestation based on this model were comparable to the data reported by other investigators using static-image equipment. Predicted menstrual age values associated with a given abdominal circumference measurement were calculated and are presented in tabular form. The variability (+/- 2 SD) in predicting menstrual age from abdominal circumference measurements is broader than that observed with the fetal biparietal diameter; nonetheless, this measurement can be useful as an adjunct in predicting menstrual age in cases in which the biparietal diameter is technically inadequate or impossible to obtain due to unusual positioning.
Abdomen Female