Fetal abdominal circumference measurements of 35 and 38 cm as predictors of macrosomia - A risk factor for shoulder dystocia

OBJECTIVE: To determine if ultrasound measurements of fetal abdominal circu mference (AC) can be used to predict macrosomic infants. STUDY DESIGN: Using a computer database, 1,996 women at greater than or equ al to 36 weeks' gestation, delivering a singleton infant and having an ultr asound examination within one week of delivery were studied. Fetal AC was e valuated to determine of it was useful in predicting the birth of a macroso mic infant, >4,000 or >4,500 g. RESULTS: AC predicted infants >4,500 g better than those >4,000 g. Almost a ll macrosomic infants >4,500 g had an AC of greater than or equal to 35 cm (68/69, or 99%), but many nonmacrosomic infants were also in this group (68 3). AC of greater than or equal to 38 cm occurred in 99 infants, and 37 of the 69 (53.6%) weighing >4,500 g were identified. Most infants (78%) with A C greater than or equal to 38 cm weighed >4,000 g. CONCLUSION: Fetal AC was very helpful in identifying potential macrosomic i nfants. If AC was <35 cm, the risk of infant birth weights >4,500 g was <1% . If AC was <greater than or equal to>38 cm, the risk was 37% (37/99), and >50% of these infants were identified (37/99, or 53.6%).