Level 1: Likely reliable evidence

Intrapartum fetal pulse oximetry to assess the fetus during labor is “noninvasive” to the fetus but requires ruptured membranes for sensor placement. A randomized trial evaluated what, if any, effect knowing the fetal pulse oximetry readouts had on rates of cesarean delivery and other clinical outcomes (N Engl J Med. 2006;355:2195-2202). An internal electronic fetal heart monitor, intrauterine pressure catheter, and fetal oxygen sensors were placed in 5,553 nulliparous women with singleton cephalic fetus at term and cervical dilatation of 2-6 cm.

Three percent (N=170) failed three attempts or 15 minutes’ worth of attempts to obtain an adequate signal; 0.8% (N=42) had prolonged fetal heart rate decelerations during attempted sensor insertion.

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After these exclusions, 5,341 women were randomized to attending-clinician knowledge vs. no knowledge of fetal pulse oximetry readouts. The oxygen sensor was removed from 505 women (9.5%) at patient or clinician request or because of technical problems. There were no significant differences in maternal outcomes comparing knowledge vs. no knowledge (masked) groups: 26.3% vs. 27.5% cesarean delivery, 31% vs. 30.5% cesarean delivery among subgroup of women with nonreassuring fetal heart rate before randomization, 14.5% vs. 14.7% forceps or vacuum-assisted delivery, 10.7% vs. 10.7% maternal chorioamnionitis, and 4.3% vs. 4.4% postpartum endometritis. There were also no significant differences in infant outcomes comparing knowledge vs. no knowledge (masked) groups: 0.2% vs. 0.1% had five-minute Apgar score <4, 0.6% vs. 0.5% had umbilical artery pH <7, 0.7% vs. 0.7% required intubation at birth, 0 vs. 0 stillbirth, 0 vs. 1 (<0.1%) neonatal death, and 3.2% vs. 3.4% composite outcome of any of the above or neonatal intensive care unit (NICU) admission longer than 48 hours. The rate of any NICU admission was 4.8% vs. 5.4%. The study method did not allow direct assessment of oximetry-device placement, but rates of cesarean delivery and adverse outcomes were higher than anticipated.