[Relationship between fetal abdominal circumference and birth weight: clinical findings in 1475 pregnancies]

To determine the reliability of the fetal abdominal circumference (FAC) measured by ultrasound as a predictor of birth weight.

FAC was measured by ultrasound within 0-7 days of delivery and the birth weight were followed in 1475 pregnant women. Statistics analysis was carried out to determine the relationship between FAC and birth weight.

Ultrasound measurement of FAC had a linear relation with birth weight, and the correlation coefficient was 0.85. Among the fetuses with FAC < 34 cm, no newborn had a weight more than 4000 g; the macrosomia rate was only 1.1% when FAC was between 34-34.9 cm. Among the fetuses with FAC between 35-35.9 cm, the average birth weight was (3691 +/- 277) g, the macrosomia rate was 14.6%; when FAC was between 36-36.9 cm, the average birth weight was (3957 +/- 256) g, the macrosomia rate was 51.0%. The macrosomia rate was 84.4% with FAC between 37-37.9 cm. When FAC > or = 38 cm the macrosomia rate was 100%. The cesarean section rate for the newborn weighing between 4000-4500 g was 71.4%, and for the fetuses weighing > or = 4500 g the cesarean section rate was 93.8%, which was significantly higher than that of fetuses weighing less than 4000 g. Only one baby who weighed 4350 g had shoulder dystocia with Erb's palsy and clavicle fracture, but recovered 2 months later.

FAC measured by ultrasound can help to evaluate the birth weight. It is useful in screening macrosomia and avoiding shoulder dystocia.