Tocolytics for suspected intrapartum fetal distress

Tocolytic drugs to help babies who have a shortage of oxygen during labour.

Most healthy babies cope well with the contractions of labour. However, some babies become short of oxygen, or cannot seem to get sufficient oxygen for their needs during labour. It can be difficult to identify these babies accurately, but they usually show some irregularity in their heartbeat patterns. If the mother lies on her back during labour, the weight of the uterus compresses her major blood vessels thus inhibiting the blood flow to the placenta and baby. If the mother is upright and moving around in labour, this can help to prevent such problems. However, the drug, syntocinon, given to push labour on more quickly, can contribute to such problems for the baby. Drugs that relax the uterus are thought to improve the blood circulation round the placenta and uterus. The review looked at the effectiveness of tocolytic drugs (drugs that relax the uterus) for helping babies in such situations prior to caesarean section. The review of trials found three studies involving just over 100 women. The studies seemed to show a benefit in terms of the acidity of the baby's blood at birth, and so showed a possible benefit in terms of 'buying time' and helping the baby whilst waiting for a caesarean section. However, the possibility of contributing to haemorrhage for the mother by relaxing the uterus needs proper investigation. So further research is needed.

Authors' conclusions: 

Betamimetic therapy appears to be able to reduce the number of fetal heart rate abnormalities and perhaps reduce uterine activity. However, there is not enough evidence based on clinically important outcomes to evaluate the use of betamimetics for suspected fetal distress.

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Background: 

Prophylactic tocolysis with betamimetics and other agents has become widespread as a treatment for fetal distress. Uterine relaxation may improve placental blood flow and, therefore, fetal oxygenation. However, there may also be adverse maternal cardiovascular effects.

Objectives: 

The objective of this review was to assess the effects of tocolytic therapy for suspected fetal distress on fetal, maternal and perinatal outcomes.

Search strategy: 

We searched the Cochrane Pregnancy and Childbirth Group Trials Register (May 2006)

Selection criteria: 

Randomised trials comparing tocolytic therapy with no treatment or treatment with another tocolytic agent for suspected fetal distress.

Data collection and analysis: 

Two review authors assessed trial quality and extracted data.

Main results: 

Three studies were included. Compared with no treatment, there were fewer failed improvements in fetal heart rate abnormalities with tocolytic therapy (relative risk (RR) 0.26, 95% confidence interval (CI) 0.13 to 0.53). Betamimetic therapy compared with magnesium sulphate showed a non-significant trend towards reduced uterine activity (RR 0.07, 95% CI 0.00 to 1.10).

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