Antenatal fetal growth from the nineteenth week. Ultrasonic study of 12 head and chest dimensions.

Fetal head, chest, and heart cross-sections obtained by ultrasonic diagnostic techniques were used for several measurements: circumference, area, and two diameters, i.e., 3,388 different measurements from 767 healthy fetuses in normal pregnancies. The mean growth for 12 fetal sizes between the nineteenth and the forty-third weeks after the LMP was computed by determining the best adjusted polynomial according to Tchebitcheff. Compared with similar measurements made previously by others on premature neonates, the sizes of healthy fetuses of the same gestational age are larger, but almost identical after the thirty-sixth week. Growth standards based on the sizes of premature neonates may be influenced by the factors responsible for premature birth.