Suppression of uterine contractions with fenoterol and its effect on fetal TcPO2 in human term labour.

Abstract

SummaryThe significance of spontaneous regular uterine contractions during the first stage of labour for fetal oxygenation was studied in 13 patients at term in uncomplicated pregnancies. The drop in transcutaneous (Po2 (tcPo2) recorded from the fetal scalp which usually followed each contraction correlated significantly with the strength of the contraction but generally was less than 2 mm Hg. The mean fetal tcPo2 in the first stage of spontaneous uncomplicated labour was 16·9±5·2 (SD) mm Hg. Suppression of contractions with intravenous fenoterol for 20 minutes did not give a statistically significant change in mean fetal tcPo2. With the administration of supplementary oxygen to the mother during continued suppression of labour, fetal tcPo2 rose significantly to 21·3±4·7 mm Hg. Maternal mean tcPo2 at the same time climbed from 83·2±10·5 to 235·1±97·8 mm Hg. While the mother responded to the infusion of fenoterol with a rise in heart rate from 92·3±15·2 to 122·8±19·7 beats per minute the fetal heart recording showed no significant change in rate or pattern. It is concluded that in the first stage of normal labour no significant impairment of fetal oxygenation is caused by uterine contractions. An important improvement in oxygen supply to the fetus, however, may be achieved in certain forms of fetal distress in labour by the combined administration of β‐sympathomimetics and supplementary oxygen to the mother.