The objective of this study was to compare the incidence of intrapartum fetal heart tracing (FHT) abnormalities and the obstetric outcome after intrathecal sufentanil (ITS) versus epidural bupivacaine (EB). During the period from April to September 1994, 129 patients who met inclusion criteria were prospectively identified during labor at a single university-affiliated hospital. Inclusion criteria included: singleton, gestational age > or = 36 wk, and cephalic presentation. In the ITS group, epidural anesthesia was not administered before 60 min after ITS. Sixty-five consecutive ITS patients were compared to 64 consecutive EB patients. Each FHT was reviewed independently by two obstetricians blinded to the type of analgesia. The FHT characteristics evaluated included baseline rate, variability, and periodic changes. No differences in the incidence of clinically significant FHT abnormalities (recurrent late decelerations and/or bradycardia) were observed between the two groups (ITS 21.5% versus EB 23.4%). The rates of clinically significant FHT abnormalities in both groups was not different when patients with hypotension and medical complications were excluded (16.9% vs 17.1%). In addition, equal rates of hypotension (18.5% vs 17.2%) were noted between the groups. In both groups there was a significantly higher risk of cesarean section in patients whose previously normal FHT became abnormal postanalgesia when compared to patients without a new onset FHT abnormality (ITS 28.6% [4/14] versus 2.0% [1/51], P < 0.01; EB 33.3% [5/15] versus 8.2% [4/49], P < 0.05). This increased risk was associated with an increase in cesarean section for nonreassuring FHT in both groups (ITS 14.3% [2/14] versus 0% [0/51], P = 0.04; EB 13.3% [2/15] versus 0% [0/49], P = 0.05). These results support the conclusion that the incidence of clinically significant FHT abnormalities and hypotension is equivalent in patients receiving ITS when compared to EB within the first hour of administration. During this period, patients should have continuous FHT monitoring since a new onset FHT abnormality unveils and alerts the physicians to a possible compromised fetal condition and a corresponding increased risk of cesarean section.