Ultrasonography and fetal growth: key perinatal factors.

To assess whether children can be predetermined prenatally to be either normally or abnormally grown and what the relationships are between intrauterine growth retardation and postnatal growth, we undertook a longitudinal study of fetal growth measuring fetuses ultrasonically. We measured 257 fetuses antenatally for femur length, biparietal diameter, head circumference (by formula calculation), abdominothoracic diameter, and body weight (by formula calculation). We chose femur length because it can be measured fairly accurately from 15 weeks' gestation to term and would represent linear growth. We noted that there is a peak length velocity before 15 weeks' gestation. In 61 fetuses, we found that by measuring the femur length within 1 week before birth, plotting that femur length against the total length measured when the baby is newly born, and multiplying the femur length by 7.0538, we derived a good estimate of total body length, with a small SD of +/- 0.0493. Thus we indicate that multiplying femur length by 7 during the second half of gestation gives a good indication and prediction of total fetal and neonatal length. Further, assessment of postnatal growth by examination of the prenatal length distance data from 15 weeks to term for femur length, and assessment of the body length of these subjects as infants from birth to 2 postnatal years, showed that the velocity curves of both phases steadily decelerate until 2 years. Also, predictive curves for fetal weight were constructed by use of Hadlock's formula for estimating fetal weight from fetal femur length and head and body measurements. It appeared that adding one biparietal diameter to the abdominothoracic diameter measurement and femur length is a better prognosticator for small-for-gestational-age infants than any measurement alone.