Prevention of macrosomia, cut-off for c/s

For decades Obstetricians have long debated the dilemma of how best to anticipate and manage a mother whose fetus weighs more than 4,000 gr. Macrosomia is defined as an estimated fetal weight or actual birth weight in excess of a threshold value, typically between 4000 and 4500 grams. A common recent definition is a weight of >45OO gr. Using such a definition 1.5% of births will be macrosomic, where if 4()0()gr is used it will be 9.9%. In contrast to macrosomia which uses an absolute cutoff, large for gestational age (LGA) is defined as actual or estimated weight in excess of a certain value standardized for gestational age. Such results are usually reported as greater than a cut-off percentile (often the 90 th percentile). A fetus at an early gestational age can be estimated to be LGA but not (yet) macrosomic. Because morbidities are related to absolute rather than relative size, macrosomia may be more important to identify than LGA.
All techniques for diagnosing macrosomic fetus has limitations. An accurate diagnosis of macrosomia can be made only weighing the newborn after delivery. Unfortunately, the prenatal diagnosis of fetal macrosomia remains imprecise.
The main risk factors for macrosomia are: prior history of macrosomia (5-10x relative risk); maternal obesity; excessive weight gain during pregnancy; multiparity, gestational age >40 weeks; ethnicity: latinas appear to be at increased risk; maternal birtweight in excess of 4()OO-5OOOgr.; age <17 years and male fetus. There has been a great effort to prevent and predict fetal macrosomia specifically in diabetic mothers. Induction of labor is also a common aproach for prevention of suspected fetal macrosomia and in order to reduce the risk of difficult operative delivery. Compared to expectant management, induction of labour for suspected macrosomia did not reduce the risk of cesarean section (odds ratio 0.85, 95% confidence interval 0.50 to 1.46) or instrumental delivery (odds ratio 0.98, 95% confidence interval 0.48 to 1.98). Perinatal morbidity was similar between groups induction of labor for suspected fetal macrosomia in non-diabetic women does not appear to alter the risk of maternal or neonatal morbidity (Cochrane 2()00;2). For non-diabetic mothers, no clinical interventions designed to treat or curb fetal growth when macrosomiais suspected have been reported.
With the exception of optimal blood glucose management in pregnancies complicated by diabetes, little is known about the prevention of macrosomia. The association between maternal weight, weight gain during pregnancy and macrosomia has led to a proposal that the optimization of maternal weight before pregnancy and limitation of weight gain during pregnancy would be useful strategies. The impact of maternal weight restrictions or outcomes is unclear.
Macrosomia remains a common complication of pregnancy; its prediction is imperfect, and there are no reliable interventions to improve outcome in uncomplicated pregnancies. Elective cesarean section is seldom a suitable alternative, and elective induction of labor appears to increase rather than decrease the cesarean section rate. Uncertainly surrounds the management of suspected fetal macrosomia in pregnant patients with diabetes concerning elective cesarean section or elective induction versus expectant management.