Mother's birth weight as a predictor of macrosomia.

The relationship between a mother's own birth weight and the risk of delivering a large for gestational age infant was studied in 1335 women. Compared to women who weighed 8 pounds or more at birth, women who weighed 6 to 7.9 pounds were only 50% as likely (p = 0.007) and women who weighed 4 to 5.9 pounds were only 15% as likely (p = 0.002) to give birth to a large for gestational age infant. When this relationship was adjusted for nine other factors known to influence birth weight, including maternal weight and weight gain during pregnancy, maternal birth weight was second only to weight gain during pregnancy in predicting the birth of large for gestational age infants. Maternal birth weight was also accurate in the prediction of macrosomia (birth weight greater than 4000 gm). Because of its ability to predict the delivery of a large infant, maternal birth weight should become part of the routine obstetric history.