Birth by vacuum extraction

Abstract

Background: In Sweden, vacuum extraction (VE) is used in almost every tenth woman to facilitate vaginal birth. VE is an important obstetric instrument that is used when shortening of the second stage of labor is necessary. VE has been associated with increased neonatal morbidity such as extracranial and cranial injuries. The outcome of the VE depends on the right selection of patients and how the VE is performed. Despite its common use, little is known about the performance of VEs, how many extractions fail, and if failure is dangerous for the child. It is also unclear whether VE delivery has negative long-term consequences for the child.

Materials and Methods: In Study I, we investigated clinical performance as described in medical records in 596 VE deliveries and compared this with recommendations in local practice guidelines for VE. Detailed data on performance was collected from six different delivery units, each contributing with information about 100 VEs performed in 2013. In Study II, we investigated if women delivered by VE receive adequate pain relief and the risk factors associated with not receiving pain relief. We identified 62,568 women delivered by VE between 1999 and 2008 in the Swedish Medical Birth Register (SMBR). In Study III, the aim was to investigate the incidence of failed VEs, risk factors for failure, and neonatal morbidity in failed VEs. We collected information on singleton pregnancies delivered at term (>36+6) by either a successful VE (n=83,671) or a failed VE (n= 4747) from the SMBR. Failed VE was defined as a VE attempt with a subsequent cesarean section (CS), the use of forceps, or both. In Study IV, the aim was to investigate if birth by VE affects cognitive development as indicated by school performance at sixteen years of age. We identified 126,032 infants born as singletons without major congenital malformations, in a vertex presentation at a gestational week of 34 or more, with Swedish-born parents, and delivered between 1990 and 1993 in the SMBR. These children were followed up at sixteen years of age in the school grade registry containing all final grades in compulsory school.

Results: Clinical performances in VEs were mostly conducted according to evidence-based safe practice; however, in a few cases, inappropriate and potentially harmful performance was used. In 6% of all extractions, more than six pulls were used to deliver the infant, and in 2.3% the procedure took more than 20 minutes. Fourteen extractions (2.3%) were conducted from a high station in the maternal pelvis. The local practice guidelines on VE were incomplete and were not updated or evidence-based. Every third woman was delivered by VE without potent pain relief. VE failure occurred in 5.4% of cases. Identified risk factors for failure were for example nulliparity, fetal malposition, and mid-pelvic extractions. Failure with the extractor was associated with increased risks of subgaleal hematoma, convulsions, and low Apgar scores but not intracranial hemorrhage in the infant. Children delivered by VE had significantly lower mean mathematics test scores and mean merit grades than children born vaginally without instruments, after adjustment for major confounders. Infants delivered by emergency cesarean section had similar results as children delivered by VE.

Conclusion: Improvements in the clinical performance of VEs can be accomplished, and practice guidelines need to be improved to support safe and evidence-based practice in VE procedures. In addition, more women should receive pain relief prior to the extraction. Failed VE can be dangerous for the child, and risk factors for failure should be closely evaluated prior to the extraction to avoid this dangerous situation. In the case of failure, a subsequent CS should be performed. Birth by VE has marginal negative effects on final school grades at 16 years of age compared with children born by spontaneous vaginal delivery. Similar marginal effects were found in children delivered by emergency CS, indicating that these lower grades are rather due to difficult labor occurring prior to birth and not to the instrument itself.