Fetal Scalp Blood Sampling in Labor: A Review EDITORIAL COMMENT

Electronic fetal monitoring and fetal scalp blood sampling (FBS) were developed in an attempt to reduce cerebral palsy caused by intrapartum asphyxia. Cardiotocography (CTG) tracings indicate the absence of intrapartum asphyxia, but interpretation of tracings varies considerably, with false-positives leading to operative vaginal delivery and emergency cesarean delivery (CD). This review summarizes the development and evaluates the effect and usefulness of FBS as a supplement to CTG. MEDLINE, EMBASE, and Cochrane databases were searched for randomized controlled trials (RCTs) comparing fetal monitoring with and without FBS as well as nonrandomized prospective studies with interventions and controls. Retrospective controlled studies, studies of outcome before and after introduction or elimination of FBS, and RCTs of other types of electronic fetal monitoring systems including FBS were selected. Data obtained focused on reduction in operative deliveries, fetal outcome, sampling success rates, and complications. From 548 citations, 38 reports were analyzed. One prospective RCT compared auscultation with CTG and CTG plus FBS and included 695 high-risk deliveries, with 232 monitored by auscultation alone, 233 by CTG alone, and 230 by CTG and FBS. The 3 groups were comparable, and no significant differences were found in fetal outcomes at delivery or the 9-month follow-up. When comparing CTG with CTG plus FBS, CD was reduced (18% vs 11%) and the relative risk for a vaginal delivery in the CTG plus FBS group was 1.07 (95% confidence interval [CI], 1.00-1.15). Although the difference was not significant, several nonrandomized retrospective studies showed that use of FBS was paralleled by a 6% to 53% reduction in the CD rate. In 9 randomized trials, auscultation was compared with CTG with and without the use of FBS. The auscultation group had 6474 monitored deliveries, and the CTG plus FBS group had 6490. The odds ratio for CD was 4.14 (95% CI, 2.29-7.15) in the studies not including FBS and 1.98 (95% CI, 1.33-2.94) in those including FBS. Neonatal outcomes did not differ significantly between the groups, except that the risk for neonatal convulsions was halved in the CTG plus FBS group (odds ratio, 0.49; 95% CI, 0.29-0.82). Twelve articles reported 37 cases of severe complications after FBS, including scalp hemorrhage in 21, with fetal collapse and death in 2, and lacerations of the fetal scalp that required suturing in 1. Severe infections including scalp abscess in 1 neonate, neonatal sepsis in 3, and retained scalpel fragments in 6 were reported. During 2003 to 2013, with the use of FBS procedures in more than 25,000 patients in a Danish cohort, no severe complications occurred. From 2005 to 2011, the use of FBS rose from 3.8% to 6% of all term and postterm deliveries. The emergency CD rate declined from 8.2% to 7.9%. The vacuum extraction rate declined significantly from 8.5% to 7.9%. The frequency of umbilical artery pH of less than 7.05 fell significantly from 0.74% to 0.34%, and that for Apgar scores of lower than 7 remained constant at approximately 0.5%. Increasing use of FBS with CTG seems to reduce operative deliveries and has prevented unnecessary emergency CDs despite nonreassuring CTG traces. Fetal scalp blood sampling provides more accurate information on fetal well-being and fetal metabolic reserves in addition to CTG before decisions are made regarding urgency of operative delivery and type of anesthesia.