Objective: To assess the validity of meconium as an indication for fetal blood sampling.
Methods: The study design was a prospective observational study in a teaching hospital. Fetal blood samples were taken from 401 women. One hundred sixty-five patients had meconium-stained amniotic fluid (77 of whom had no cardiotocographic abnormalities). In the remaining 236 patients, the indication for fetal blood sampling was cardiotocographic abnormalities without meconium. The main outcome measures were the values of pH and base excess obtained at fetal blood sampling, 1-minute Apgar scores, and umbilical artery pH values.
Results: Patients with meconium alone as an indication for fetal blood sampling had higher scalp sample pH values (P < .001) and 1-minute Apgar scores (P < .01) than laboring patients with both meconium and cardiotocographic abnormalities. The patients with meconium alone had higher scalp pH values than patients with cardiotocographic abnormalities but no meconium (P < .001). In only two patients with meconium alone was a fetal scalp pH less than 7.20 (both infants had good Apgar scores at delivery). However, when cardiotocographic abnormalities were present, the finding of meconium was significant, resulting in lower 1-minute Apgar scores (P < .01) despite a lack of difference in fetal blood sample pH values.
Conclusion: In the absence of cardiotocographic abnormalities, meconium is not an indication for fetal blood sampling.