PATIENTS RESPECTIVELY AND METHODS: In the HEPE 619 242 births have been analysed (1990 - 2000) to calculate the incidence of a birthweight between 4000 and 4499 g and of a weight > or = 4500 g in relationship to maternal obesity, high maternal weight gain and of a duration of pregnancy more than 298 days.
Results: The risk of a macrosomia > or = 4500 g is in cases of obesity 3.4 times higher, in cases of obesity and prolongation of pregnancy 6.6 times higher and in the presence of all 3 risk factors 10 times higher. Data of the Frauenklinik Wiesbaden (HSK) (n = 6075 births) complete the results, because a correlation between macrosomia, shoulder dystocia and a damage to the plexus brachialis has been found. The incidence of a damage to the plexus brachialis is in case of a shoulder dystocia and a birth weight of < or = 4000 g 6.3%, at a birth weight between 4000-4499 g 25% and in newborns with a weight > or = 4500 g 40%.
Conclusions: Because of the low sensitivity (60%) of the ultrasonic weight measurement the 3 maternal risk factors--if they exist--of a shoulder dystocia and of a damage of the plexus brachialis should be discussed with the pregnant woman to help her about the decision of an alternative cesarean section. Still one third of the newborns weigh more than 4000 g if all 3 maternal risk factors exist.