Prophylactic oral betamimetics for preventing preterm labour in singleton pregnancies

There are insufficient data on use of betamimetic drugs given by mouth to reduce preterm birth in women at increased risk of preterm labour and carrying one baby.

Women sometimes go into labour early and babies are born prematurely (before 37 weeks). These babies are at increased risk of health problems and the earlier a baby is born the higher the risk. Babies born before 32 weeks have considerable problems, with those born before 28 weeks being at most risk. These babies can suffer from problems with breathing, bleeding, gut and intestines. They are also at increased risk of cerebral palsy or long-term handicap, and some babies do not survive even the early weeks. Babies need special care, sometimes intensive care, and this can be quite traumatic for parents. Preterm birth occurs in around 6% to 10% of births. Many interventions have been assessed to try to improve outcomes for these babies; this review looks at a group of drugs called betamimetics given by mouth in women at increased risk and carrying one baby. These drugs aim to reduce and inhibit labour contractions. However, they do have side effects which include nausea, vomiting, tremor, headaches and shortness of breath. The review of studies found only one trial involving 64 women. There is therefore insufficient evidence to support the use of these drugs to reduce preterm labour and birth.

Authors' conclusions: 

There is insufficient evidence to support or refute the use of prophylactic oral betamimetics for preventing preterm birth in women at high risk of preterm labour with a singleton pregnancy.

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Background: 

Preterm birth occurs in up to 6% to 10% of all births and is the major complication of pregnancy associated with perinatal mortality and morbidity. Previous preterm delivery is a strong predictor for preterm labour, and the earlier the birth, the more likely it is to be repeated at the same gestation. In the acute setting, betamimetics can decrease contraction frequency or delay preterm birth by 24 to 48 hours.

Objectives: 

To assess the effectiveness of prophylactic oral betamimetics for the prevention of preterm labour and birth for women with singleton pregnancies at high risk of preterm delivery.

Search strategy: 

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (October 2010) and reference lists.

Selection criteria: 

Randomised controlled trials in singleton pregnancies at high risk of preterm labour comparing prophylactic oral betamimetics with placebo or any intervention with the specific aim of preventing preterm birth.

Data collection and analysis: 

Two authors independently assessed trial quality and extracted data.

Main results: 

One trial (64 singleton pregnancies) was included. The trial compared the oral betamimetic agent isoxuprine with placebo. No difference was seen for perinatal mortality rate (risk ratio (RR) 4.74, 95% confidence interval (CI) 0.50 to 45.00). There was no evidence of an effect of oral betamimetic agents in reduction of spontaneous onset of preterm labour (RR 1.07, 95% CI 0.14 to 8.09) or preterm birth, less than 37 weeks' gestation. There was no significant association between the use of oral betamimetics and side effects sufficient to stop therapy (RR 2.51, 95% CI 0.59 to 10.76). No differences were found for infant outcomes; birthweight less than 2500 grams (RR 1.74, 95% CI 0.44 to 6.87) or neonatal death (RR 4.74, 95% CI 0.50 to 45.00). This trial had adequate methodological quality; however the sample size was inappropriate to determine any significance in neonatal outcome differences between the treatment groups.

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