Growth velocity of the biparietal diameter, abdominal transverse diameter and femur length in the fetal period.

In this study, fetal growth rates of the biparietal diameter (BPD), abdominal transverse diameter (ATD) and femur length were established from 4333 ultrasound examinations. The age of the fetuses ranged from 7 to 40 gestational weeks. The growth rates were computed by periods of 3 weeks, and the velocity curves were plotted with their 95% confidence interval. Results displayed multiphasic patterns of growth velocity for these variables, with a common peak of velocity at about 16 weeks. Between 16 and 28 weeks, growth velocity of femur length decreased, while the ATD and the BPD grew at the same constant rate. From 28 to 37 weeks, only the ATD maintained a high rate of growth. After 37 weeks, all growth rates decreased abruptly. In all cases, no sex differences in growth velocity were found.