Growth of the fetal kidney assessed by real-time ultrasound.

We present a method for measuring the size of the fetal kidney by real-time ultrasound. We examined 241 normal pregnancies and 27 pregnancies with intrauterine growth retardation by this method. The cross-sectional area of the kidney (KA) increases linearly from 20 weeks to term whereas the relative size of the kidney to the abdomen (KA/AA ratio) remains constant during this period. Growth-retarded fetuses had significantly smaller KA values than normal fetuses but their KA/AA ratios were generally in the normal range. The results showed that the growth of the fetal kidney correlates well with that of the abdomen and could be an additional parameter for the detection of intrauterine growth retardation.