The effect of uterine contractions on fetal oxygen saturation

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Abstract
Objective To find out what happens to fetal arteriolar oxygen saturation during a uterine contraction. Design Prospective observational study. Setting Labour ward, St James's University Hospital, Leeds. Subjects Eighteen women in normal labour monitored with a fetal scalp surface pulse oximetry sensor, an intrauterine pressure catheter, and a head to cervix force transducer. Methods The effect of intrauterine pressure and head to cervix force on fetal arteriolar oxygen saturation was examined using time series analysis and a regression model of 159 contractions. Outcome measure Fetal oxygen saturation during a contraction. Results The average oxygen saturation drops after a contraction. The greatest drop in oxygen saturation is reached 92 s after the peak of a contraction and takes approximately 1 min 30 s to recover (P= 0.036). Conclusion Uterine contractions during normal labour affect fetal oxygen saturation.