Fetal oxygen saturation during epidural and paracervical analgesia

We wanted to assess changes in fetal oxygenation during maternal epidural or paracervical analgesia in labor.

A prospective, open and non-randomized study. Twenty healthy parturients were enrolled before they asked for pain relief. Informed consent was obtained. Fetal and maternal oxygen saturations were measured before and up to 1 h after the initiation of analgesia. Fetal oximetry was performed with the Nellcor N-400 oximeter+FS-14B fetal oxygen sensor (Nellcor Puritan Bennett, Pleasanton, California, USA). Maternal oximetry was done with Datex Satlite portable monitor (Datex, Finland). Visual analog scale was used for assessing pain relief. Two-way analysis of variance and students t-test were used for statistical analyses.

Fetal oxygenation initially improved in both groups. The saturation then returned to baseline in both groups. In the epidural group, the values remained at baseline or slightly below, while in the paracervical group the saturation remained a little higher than baseline (p=0.009). No change was seen in maternal oxygenation or heart rate. No change in fetal heart rate was found either. Epidural block was superior to paracervical block with respect to pain relief (p=0.002).

There was a small but significant difference in fetal oxygenation between epidural and paracervical groups during the observation period. The magnitude of the difference is hardly clinically significant. A larger, randomized study is needed to elucidate the mechanisms behind this finding.