| Excerpt from The WHO Reproductive Health Library | Published by Update Software Ltd. |
This commentary covers two Cochrane reviews that focus on medical treatments to inhibit preterm labour.
One of them assesses the effects of calcium channel blockers on maternal, fetal and neonatal outcomes when administered as a tocolytic agent to women during preterm labour. It makes two comparisons: (i) calcium channel blockers versus placebo or no intervention; and (ii) the effects of any dihydropiridine class calcium channel blockers (e.g. nifedipine and nicardipine) versus any betamimetic agent. Twelve randomized controlled trials involving 1029 women are included in the review, with nine of them (817 women) being evaluated in the subgroup analysis for comparison of dihydropiridine class of calcium channel blockers versus any betamimetic agent.
The use of calcium channel blockers, when compared with any other tocolytic agent, showed a statistically significant decrease in the number of women giving birth within seven days of initiation of the treatment (relative risk [RR] 0.76; 95% confidence interval [CI] 0.60–0.97). Outcomes such as pregnancy prolongation (weighted mean difference [WMD] 3.83 days; 95% CI 3.04-10.70), birth prior to 37 weeks gestation (RR 0.95; 95% CI 0.83-1.09) and birth within 48 hours of initiation of treatment (RR 0.80; 95% CI 0.61-1.05) favoured calcium channel blockers, although the latter two outcomes did not reach statistical significance. For every 11 women treated with a calcium channel blocker rather than another tocolytic one less can be expected to deliver within seven days (number needed to treat [NNT]= 11; 95% CI 6-100). Calcium channel blockers are associated with fewer maternal adverse drug reactions (RR 0.32; 95% CI 0.24-0.41) and cessation of treatment due to side-effects (RR 0.14; 95% CI 0.05-0.44).
The use of calcium channel blockers resulted in statistically and clinically significant benefits for the baby. Neonatal respiratory distress syndrome (RR 0.63; 95% 0.46-0.88) necrotising enterocolitis (RR 0.21; 95% 0.05-0.96), intraventricular haemorrhage (RR 0.59; 95% CI 0.36-0.98) and neonatal jaundice (RR 0.73; 95% CI 0.57-0.93) were all reduced. The risk reduction for the outcome of respiratory distress syndrome gives a NNT value of 14 (95% CI 8-50) and for intraventricular haemorrhage 13 (95% CI 7-100).
The second review evaluated the effects of oxytocin receptor antagonists (atosiban) for inhibiting preterm labour (1). Two trials compared atosiban with placebo and four trials compared atosiban with betamimetics. When compared with placebo, atosiban resulted in lower birth weight (WMD -138.31 gm; 95% CI – 248.76 to -27,86), an increase in infant death at 12 months of age (RR 6.15;95% CI 1.39–27.22) and an increase in maternal adverse drug reaction (RR 4.02; 95%CI 2.05 to 7.85). There were more women in earlier gestational ages in the atosiban group which could explain the increased number of infant deaths.
Compared with betamimetics more atosiban-exposed infants had birth-weights under 1500 gm (RR 1.96;95% CI 1.15–3.35), but neither neonatal mortality nor neonatal morbidity differed. Atosiban was associated with significantly less maternal drug reactions when compared with betamimetics (RR 0.04; 95% CI 0.02–0.11). Moreover, atosiban did not reduce the incidence of delivery before 48 hours after initiation of treatment, respiratory distress syndrome and admission to neonatal intensive care.
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