The prediction and prevention of intrapartum fetal asphyxia in term pregnancies

OBJECTIVE: This study was undertaken to examine the roles of clinical risk scoring, electronic fetal heart rate monitoring, and fetal blood gas and ac id-base assessment in the prediction and prevention of intrapartum fetal as phyxia in term pregnancies. STUDY DESIGN: The outcomes of 166 term pregnancies with biochemically confi rmed fetal asphyxia (umbilical artery base deficit at delivery, >12 mmol/L) were examined. This population included 83 pregnancies delivered abdominal ly matched with 83 pregnancies delivered vaginally. Antepartum and intrapar tum clinical risk factors and neonatal complications were documented. Fetal assessments included fetal heart rate patterns in the fetal heart rate rec ord and fetal capillary blood gas and acid-base assessments. Fetal asphyxia was classified as mild, moderate, or severe on the basis of umbilical arte ry base deficit (cutoff >12 mmol/L) and neonatal encephalopathy and other o rgan system complications. RESULTS: Fetal asphyxial exposures were as follows: mild, 140; moderate, 22 ; and severe, 4. Intervention and delivery during the first or second stage of labor occurred in 98 of the 166 pregnancies. Predictive fetal heart rat e patterns were the primary indication leading to intervention and delivery during the first or second stage of labor. Clinical risk factors when pres ent were secondary indications in the clinical decision to intervene. Fetal blood gas and acid-base assessment was a useful supplementary test in 41 p regnancies. Intervention and delivery may have prevented the progression of mild asphyxia in 78 pregnancies and may have modified the degree of modera te or severe asphyxia in 20 pregnancies. CONCLUSION: Although fetal heart rate patterns will not discriminate all as phyxial exposures, continuous fetal heart rate monitoring supplemented by f etal blood gas and acid-base assessment can be a useful fetal assessment pa radigm for intrapartum fetal asphyxia. Such an assessment paradigm will not prevent all cases of moderate or severe fetal asphyxia. However, predictio n and diagnosis with intervention and delivery during the first or second s tage of labor could prevent the progression of mild asphyxia to moderate or severe asphyxia in some cases.