SUPPRESSION OF UTERINE CONTRACTIONS WITH ENOTEROL AND ITS EFFECT ON FETAL TcPo₂ IN HUMAN TERM LABOUR

Abstract

Summary The 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.

Relation between frequency of uterine contractions and human fetal cerebral oxygen saturation studied during labour by near infrared spectroscopy

“…Many studies have shown that uterine contractions are associated with a decrease in uterine blood flow (Borell et al 1965; Brotanek et al 1969; Harbert 1982; Brar et al 1988). How this affects the fetus depends on the frequency and duration of the contractions: the normal first stage of labour does not cause a change in transcutaneous pO 2 (Schneider et al 1980), whilst excessive uterine activity, particularly as a result of the use of oxytocin, is associated with changes in fetal heart rate and meconium staining of amniotic fluid (Hess & Hon 1960; Liston & Campbell 1974). However, these are relatively crude indicators of fetal oxygenation and direct evidence of a relation between uterine activity and oxygenation is lacking.…”

Fetal Cardiac Function in Response to Long‐Term Maternal Terbutalin Treatment

“…Probably related to the compounds selected and the durations of infusions examined, various results have been obtained. Some investigators found FHR to increase (ll), while others found FHR unchanged (10,12).…”

Physiological insights based on fetal tcPo2 monitoring

“…At the end of a pause between two contractions fetal transcutaneous Po2 has its highest value. Addltlonal evidence that the observed fluctuations in fetal tcPo2 are the result of the contractions is shown, when labour is stopped by infusion of betamimetics (2). Correlation between intrauterine pressure and the fall in tcPo2 in 8 cases.…”