Fetal macrosomia--a continuing obstetric challenge.

Background: Macrosomic fetuses represent a continuing challenge in obstetrics.

Objectives: We studied maternal risk factors of fetal macrosomia and maternal and infant outcome in such cases.

Methods: A retrospective cohort study was carried out with a total of 26,961 singleton pregnancies between 1989 and 2001. Records of 886 mothers who gave birth to live born infants weighing > or =4,500 g were compared to those of 26,075 mothers with normal weight (<4,500 g) infants. Multiple regression analysis was used to identify independent reproductive risk factors. Perinatal complications were also assessed.

Results: The incidence of fetal macrosomia was 3.4%. Diabetes, previous macrosomic birth, postdatism (>42 weeks of gestation), obesity (BMI > 25 before pregnancy), male infant, gestational diabetes mellitus, and non-smoking were independent risk factors of fetal macrosomia, with adjusted risks of 4.6, 3.1, 3.1, 2.0, 1.9, 1.6, 1.4, respectively. In the macrosomic group, birth and maternal traumas occurred significantly more often than in the control group. However, records of subsequent pregnancies (n = 250) after the study period showed that a previous uncomplicated birth appeared to decrease complication risks.

Conclusions: Most cases of fetal macrosomia occur in low-risk pregnancies and evaluation of maternal risks cannot accurately predict which women will eventually give birth to an overweight newborn. After an uncomplicated birth of a macrosomic infant, vaginal delivery may be a safe option for the infant and mother.