Suspected macrosomia: will induction of labour modify the risk of caesarean delivery?



I was interested to read the recent study by Cheng et al.1 suggesting that induction of labour might reduce the caesarean section rate associated with macrosomia. The study question is built on two false premises: namely that one can accurately diagnose macrosomia prenatally, and secondly that one can study any one variable, such as induction, in relation to caesarean rates using birth certificate data. Both manual and ultrasound fetal weight estimation at term have poor sensitivity and specificity.2 Seventeen documented variables simultaneously affect caesarean rates, making it impossible to use birth certificate data to control for all of them.3

In the absence of improved outcomes resulting from induction for macrosomia,4 one must question the continued use of this protocol, in light of the fact that induction is an independent risk factor for postpartum haemorrhage (PPH).5 The majority of obstetrical brachial plexus palsy (OBPP) cases are not associated with macrosomia.6

Of the 4 130 665 US women giving birth in the study year, 743 520 were primiparae delivering a single fetus at term, with about 30% of them delivering by caesarean section, leaving about 500 000 who delivered vaginally.This study looked at 132 112 (26%) babies who were both macrosomic and delivered vaginally to primiparae. Nutritional counselling should be at least suggested as something to consider when macrosomia affects one in every four births.