Vacuum extraction in fetal macrosomia: registry data are useful

Sir, We thank Dr. McQuivey for his comments (1) and interest in our work (2). Dr. McQuivey’s point that the Swedish Medical Birth Register lacks detailed information is well-taken and causal relations among vacuum extraction, birthweight and neonatal complications are difficult to prove using our study design. The register does lack information about some important aspects of vacuum deliveries, for instance cup placement, number of tractions and extraction time. Nevertheless, the register provides large study populations giving the unique opportunity to study rare outcomes. Dr. McQuivey’s concern that the lack of data on the placement of the vacuum device on the fetal head may have influenced our results and their interpretation seems unjustified. Although correct cup placement is important for a successful vacuum delivery (3), there is no reason to assume that the placement of the vacuum cup differed between the birthweight categories and thereby biased our findings. Dr. McQuivey also commented on the seemingly unexpected low failure rate of vacuum delivery in our study population (3.5%). In a recent Swedish study the failure rate of vacuum delivery increased from 4.9% in 1999 to 5.4% in 2010 (4). However, we excluded all deliveries where the position of the fetal head was not documented or it was neither occiput anterior nor posterior, and all deliveries where forceps were used subsequent to a failed vacuum attempt, which explains the lower failure rate found by us. Dr. McQuivey further questions the rationale of combining successful vacuum deliveries and cesarean deliveries following