The relationship between mean abdominal diameter and femur length in normal and impaired fetal growth.

The relationship of fetal mean abdominal diameter (MAD) to fetal femur length (FL) in clinically normal pregnancies and 37 cases of intrauterine growth retardation (IUGR) was studied. The normal relationship of FL to MAD is closely described by the equation: log (MAD) = 3.326 + (0.185 X FL). r = .953, P less than .001. In the growth retarded infants, 59% of the abdominal measurements fell below the lower 75% confidence limit. Of the abdominal measurements derived from infants with birthweight greater than 2 SD below the mean for gestational age, 86% fell below the lower 75% confidence limit. These data show the MAD is selectively depressed in many, but not all cases of IUGR and particularly in the more severely affected infant, but the technique is not sufficiently discriminant to be used by itself for the detection of IUGR. Detection of an anomaly of this relationship would be strong supportive evidence of IUGR independent of gestational age and possibly identifies infants growth retarded specifically due to chronic deprivation.