The effects of epidural analgesia and uterine contractions on fetal oxygen saturation during the first stage of labour

The aim of this study was to investigate the effects of (1) maternal epidural analgesia and (2) uterine contractions on fetal oxygen saturation. After informed consent 18 women were included in our prospective, non-blinded, observational study. After 30 min of monitoring fetal oxygen saturation and uterine contractions, all the parturients, at cervical dilatation ≥3 cm, received epidural analgesia for labour: a Pajunk epidural catheter was passed through a 17-gauge Tuohy needle and left in the lumbar epidural space (insertion level L3-4 or L2-3). Sufentanil 10 μg and 0.1% ropivacaine 15 mL were injected into the epidural catheter. A second and third 15-mL epidural dose of 0.1% ropivacaine were administered on patient demand. Fetal oxygen saturation was unaffected by epidural analgesia and there was no change in fetal SpO₂ following an uncomplicated epidural top-up. SpO₂ values (%) 30 s before, during and after contraction were 47.6 ± 2.4, 52.5 ± 5.3 and 42.9 ±7.2 respectively. These changes were significant. A contraction appeared to inject a bolus of oxygenated blood into the fetus, causing an initial increase in fetal oxygenation followed by a decline. The lowest SpO₂ values observed occurred 120 s after the start of contractions.