Neonatal complications following birth by vacuum extraction

Sammanfattning: Background: Vacuum extraction is a common method of delivery presently accounting for approximately 7 percent of all deliveries in Sweden. It is considered an important and safe obstetric procedure, although both maternal and neonatal complications exist. There is a lack of knowledge about if and how specific risk factors contribute to neonatal complications after vacuum assisted delivery. Therefore, the aim of this thesis was to identify risk factors for neonatal complications following vacuum assisted delivery, ultimately in order to increase infant safety. Methods: Study I, II and IV were population-based cohort studies with data from the Swedish Medical Birth Register. In the first study we investigated neonatal outcomes after preterm delivery by VE. The outcomes were extracranial hemorrhage, intracranial hemorrhage, convulsions, encephalopathy and brachial plexus injury. In the second study, we investigated the relationship between birthweight at increasing levels and neonatal complications of infants delivered by vacuum extraction at term. The following outcomes were assessed: five minute Apgar score <7, convulsions, intracranial hemorrhage and brachial plexus injury. In the fourth study, maternal and obstetric risk factors for nonhemolytic hyperbilirubinemia in term newborn infants were assessed. The exposures were a large number of maternal and obstetric factors, including country of birth, mode of delivery and gestational age. The outcome was neonatal hyperbilirubinemia. In the third study, a matched case-control design was used to investigate the association between characteristics of the extraction and intracranial hemorrhage. Cases diagnosed with intracranial hemorrhage after delivery by vacuum extraction at term were included and compared to controls without intracranial hemorrhage delivered by vacuum extraction. The exposure was protracted vacuum extraction, defined as vacuum duration > 15 min, > 6 pulls or > 2 cup detachments. Results: The rates of serious neonatal complications were low in all studies, although some risk factors were identified. Firstly, preterm infants delivered by vacuum extraction had the highest adjusted odds ratios for the outcomes studied, compared with infants delivered by spontaneous vaginal delivery or caesarean section during labor. Secondly, the rates of complications increased with increasing birthweight among term infants delivered by vacuum extraction. Thirdly, protracted extractions occurred more often among cases diagnosed with intracranial hemorrhage than among controls. Compared to extractions adhering to guidelines, the risk of intracranial hemorrhage was nine-fold among infants exposed to a protracted extraction. And lastly, the risk of nonhemolytic neonatal hyperbilirubinemia varied substantially depending on maternal and obstetric risk factors. Conclusions: Easy-available maternal and obstetric risk factors can be used to predict large variations in the risk of hyperbilirubinemia, information that is useful in timing of hospital discharge and follow-up. We also identified some situations that call for cautious use of vacuum extraction: preterm deliveries, including 34-36 gestational weeks, and deliveries with clinical suspicion of a large fetus. Furthermore, the importance of abandoning a difficult extraction in time is emphasized by the strong association between protracted extractions and intracranial hemorrhage.