Purpose The purpose of this study was to identify risk factors and complications associated with macrosomia in a large population from a single institution.
Method This study is a retrospective review of deliveries performed at a single institution from January 1, 1982 to December 31, 2001. Cases with incomplete records, inaccurate birth weights, hydrops, hydrocephaly and anencephaly, birth weights < 500 g, were excluded and included only African-Americans or Mexican-Americans from 25 to 44 weeks between 1981 to 2001. Univariate and multiple logistic regression analysis were done as indicated. Macrosomia was defined as > 4,000 g.
Results There were 8,753 (11.2%) cases of macrosomia in 78,092 deliveries; 80.3% delivered between 37 and 41 weeks and 18.4% between 42 and 44 weeks. The cesarean section rate was 24.1% for macrosomia and 12.9% for controls. Of cases with shoulder dystocia 61% had macrosomia. Independent predictors of macrosomia were obesity 5.5-fold, diabetes 2.4-fold, Mexican-Americans 2.7-fold, advanced maternal age (AMA) 1.4-fold, post-term pregnancy 2.0-fold, multipara 2.2-fold, male 1.6-fold, and prenatal care (PNC) 1.2-fold. Factors that independently decreased the risk of macrosomia include multiple pregnancy, cocaine abuse, abruption, placenta previa, hypertensive disorders. Macrosomia also independently increased the risk of shoulder dystocia by 12.5-fold, polyhydramnios 4.7 times, cesarean section 2.6 times, 4th-degree perineal lacerations 2.7 times, and dystocia 1.5 times. The risk of oligohydramnios, fetal distress, and fetal demise was significantly decreased. There were no major differences in risk factors when term was compared to post-term macrosomia.
Conclusion Older obese diabetic Mexican-American multiparas are at increased risk of macrosomia. Complications, especially those with vascular pathology, decrease the risk of macrosomia. This study confirms the significant association with shoulder dystocia and other labor complications.