10: Maintenance nifedipine vs. placebo: A prospective, double blind trial

Tocolytics for delaying preterm birth: a network meta-analysis (0924)

BACKGROUND

Preterm birth is the leading cause of death in newborns and children. Tocolytic drugs aim to delay preterm birth by suppressing uterine contractions to allow time for administration of corticosteroids for fetal lung maturation, magnesium sulphate for neuroprotection, and transport to a facility with appropriate neonatal care facilities. However, there is still uncertainty about their effectiveness and safety.

OBJECTIVES

To estimate relative effectiveness and safety profiles for different classes of tocolytic drugs for delaying preterm birth, and provide rankings of the available drugs.

SEARCH METHODS

We searched Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov (21 April 2021) and reference lists of retrieved studies.

SELECTION CRITERIA

We included all randomised controlled trials assessing effectiveness or adverse effects of tocolytic drugs for delaying preterm birth. We excluded quasi- and non-randomised trials. We evaluated all studies against predefined criteria to judge their trustworthiness.

DATA COLLECTION AND ANALYSIS

At least two review authors independently assessed the trials for inclusion and risk of bias, and extracted data. We performed pairwise and network meta-analyses, to determine the relative effects and rankings of all available tocolytics. We used GRADE to rate the certainty of the network meta-analysis effect estimates for each tocolytic versus placebo or no treatment.

MAIN RESULTS

This network meta-analysis includes 122 trials (13,697 women) involving six tocolytic classes, combinations of tocolytics, and placebo or no treatment. Most trials included women with threatened preterm birth, singleton pregnancy, from 24 to 34 weeks of gestation. We judged 25 (20%) studies to be at low risk of bias. Overall, certainty in the evidence varied. Relative effects from network meta-analysis suggested that all tocolytics are probably effective in delaying preterm birth compared with placebo or no tocolytic treatment. Betamimetics are possibly effective in delaying preterm birth by 48 hours (risk ratio (RR) 1.12, 95% confidence interval (CI) 1.05 to 1.20; low-certainty evidence), and 7 days (RR 1.14, 95% CI 1.03 to 1.25; low-certainty evidence). COX inhibitors are possibly effective in delaying preterm birth by 48 hours (RR 1.11, 95% CI 1.01 to 1.23; low-certainty evidence). Calcium channel blockers are possibly effective in delaying preterm birth by 48 hours (RR 1.16, 95% CI 1.07 to 1.24; low-certainty evidence), probably effective in delaying preterm birth by 7 days (RR 1.15, 95% CI 1.04 to 1.27; moderate-certainty evidence), and prolong pregnancy by 5 days (0.1 more to 9.2 more; high-certainty evidence). Magnesium sulphate is probably effective in delaying preterm birth by 48 hours (RR 1.12, 95% CI 1.02 to 1.23; moderate-certainty evidence). Oxytocin receptor antagonists are probably effective in delaying preterm birth by 48 hours (RR 1.13, 95% CI 1.05 to 1.22; moderate-certainty evidence), are effective in delaying preterm birth by 7 days (RR 1.18, 95% CI 1.07 to 1.30; high-certainty evidence), and possibly prolong pregnancy by 10 days (95% CI 2.3 more to 16.7 more). Nitric oxide donors are probably effective in delaying preterm birth by 48 hours (RR 1.17, 95% CI 1.05 to 1.31; moderate-certainty evidence), and 7 days (RR 1.18, 95% CI 1.02 to 1.37; moderate-certainty evidence). Combinations of tocolytics are probably effective in delaying preterm birth by 48 hours (RR 1.17, 95% CI 1.07 to 1.27; moderate-certainty evidence), and 7 days (RR 1.19, 95% CI 1.05 to 1.34; moderate-certainty evidence). Nitric oxide donors ranked highest for delaying preterm birth by 48 hours and 7 days, and delay in birth (continuous outcome), followed by calcium channel blockers, oxytocin receptor antagonists and combinations of tocolytics. Betamimetics (RR 14.4, 95% CI 6.11 to 34.1; moderate-certainty evidence), calcium channel blockers (RR 2.96, 95% CI 1.23 to 7.11; moderate-certainty evidence), magnesium sulphate (RR 3.90, 95% CI 1.09 to 13.93; moderate-certainty evidence) and combinations of tocolytics (RR 6.87, 95% CI 2.08 to 22.7; low-certainty evidence) are probably more likely to result in cessation of treatment. Calcium channel blockers possibly reduce the risk of neurodevelopmental morbidity (RR 0.51, 95% CI 0.30 to 0.85; low-certainty evidence), and respiratory morbidity (RR 0.68, 95% CI 0.53 to 0.88; low-certainty evidence), and result in fewer neonates with birthweight less than 2000 g (RR 0.49, 95% CI 0.28 to 0.87; low-certainty evidence). Nitric oxide donors possibly result in neonates with higher birthweight (mean difference (MD) 425.53 g more, 95% CI 224.32 more to 626.74 more; low-certainty evidence), fewer neonates with birthweight less than 2500 g (RR 0.40, 95% CI 0.24 to 0.69; low-certainty evidence), and more advanced gestational age (MD 1.35 weeks more, 95% CI 0.37 more to 2.32 more; low-certainty evidence). Combinations of tocolytics possibly result in fewer neonates with birthweight less than 2500 g (RR 0.74, 95% CI 0.59 to 0.93; low-certainty evidence). In terms of maternal adverse effects, betamimetics probably cause dyspnoea (RR 12.09, 95% CI 4.66 to 31.39; moderate-certainty evidence), palpitations (RR 7.39, 95% CI 3.83 to 14.24; moderate-certainty evidence), vomiting (RR 1.91, 95% CI 1.25 to 2.91; moderate-certainty evidence), possibly headache (RR 1.91, 95% CI 1.07 to 3.42; low-certainty evidence) and tachycardia (RR 3.01, 95% CI 1.17 to 7.71; low-certainty evidence) compared with placebo or no treatment. COX inhibitors possibly cause vomiting (RR 2.54, 95% CI 1.18 to 5.48; low-certainty evidence). Calcium channel blockers (RR 2.59, 95% CI 1.39 to 4.83; low-certainty evidence), and nitric oxide donors probably cause headache (RR 4.20, 95% CI 2.13 to 8.25; moderate-certainty evidence).

AUTHORS' CONCLUSIONS

Compared with placebo or no tocolytic treatment, all tocolytic drug classes that we assessed (betamimetics, calcium channel blockers, magnesium sulphate, oxytocin receptor antagonists, nitric oxide donors) and their combinations were probably or possibly effective in delaying preterm birth for 48 hours, and 7 days. Tocolytic drugs were associated with a range of adverse effects (from minor to potentially severe) compared with placebo or no tocolytic treatment, although betamimetics and combination tocolytics were more likely to result in cessation of treatment. The effects of tocolytic use on neonatal outcomes such as neonatal and perinatal mortality, and on safety outcomes such as maternal and neonatal infection were uncertain.

Maintenance therapy with calcium channel blockers for preventing preterm birth after threatened preterm labour

BACKGROUND

Calcium channel blocker maintenance therapy is one of the types of tocolytic therapy that may be used after an episode of threatened preterm labour (and usually an initial dose of tocolytic therapy) in an attempt to prevent the onset of further preterm contractions.

OBJECTIVES

To assess the effects of calcium channel blockers as maintenance therapy on preventing preterm birth after threatened preterm labour.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 May 2013) and reference lists of retrieved studies.

SELECTION CRITERIA

Randomised controlled trials of calcium channel blockers used as maintenance therapy to prevent preterm birth after threatened preterm labour, compared with placebo or no treatment.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed study eligibility, extracted data and assessed the risk of bias of included studies.

MAIN RESULTS

We included six trials that enrolled 794 women and their babies and all assessed nifedipine as calcium channel blocker maintenance therapy. The six trials were judged to be at a moderate risk of bias overall. No differences in the incidence of preterm birth (risk ratio (RR) 0.97; 95% confidence interval (CI) 0.87 to 1.09; five trials, 681 women), birth within 48 hours of treatment (RR 0.46; 95% CI 0.07 to 3.00; two trials, 128 women) or neonatal mortality (average RR 0.75; 95% CI 0.05 to 11.76; two trials, 133 infants) were seen when nifedipine maintenance therapy was compared with placebo or no treatment. No stillbirths were reported in the one trial that provided data for this outcome. No trials reported on longer-term follow-up of infants.Women receiving nifedipine maintenance therapy were significantly more likely to have their pregnancy prolonged (mean difference (MD) 5.35 days; 95% CI 0.49 to 10.21; four trials, 275 women); however, no differences between groups were shown for birth at less than 34 weeks' gestation, birth at less than 28 weeks' gestation, birth within seven days of treatment, or gestational age at birth. No significant differences were shown between the nifedipine and control groups for any of the secondary neonatal morbidities reported. Similarly, no significant differences were seen for the outcomes relating to the use of health services, except for in one trial, where infants whose mothers received nifedipine were significantly more likely to have a longer length of hospital stay as compared with infants born to mothers who received a placebo (MD 14.00 days; 95% CI 4.21 to 23.79; 60 infants).

AUTHORS' CONCLUSIONS

Based on the current available evidence, maintenance treatment with a calcium channel blocker after threatened preterm labour does not prevent preterm birth or improve maternal or infant outcomes.

Maintenance therapy with calcium channel blockers for preventing preterm birth after threatened preterm labour

BACKGROUND

Calcium channel blocker maintenance therapy is one of the types of tocolytic therapy used after an episode of threatened preterm labour (and usually an initial dose of tocolytic therapy) in an attempt to prevent the onset of further preterm contractions.

OBJECTIVES

To assess the effects of calcium channel blockers as maintenance therapy on preventing preterm birth after threatened preterm labour.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group trials register (31 March 2004); MEDLINE (1966 to March 2004) and DARE (June 2003).

SELECTION CRITERIA

Randomised controlled trials of calcium channel blockers used as maintenance therapy to prevent preterm birth after threatened preterm labour, compared with alternative drug therapy, placebo or no treatment.

DATA COLLECTION AND ANALYSIS

Two reviewers independently applied the selection criteria, extracted data from the included study and assessed study quality.

MAIN RESULTS

One trial of 74 women was included. No difference in the incidence of preterm birth was found when calcium channel blocker (nifedipine) maintenance therapy was compared with no treatment. Twenty-five women out of 37 in each group gave birth before 37 weeks (relative risk 1.00, 95% confidence interval 0.73 to 1.37). The trial did not report stillbirths and neonatal deaths prior to discharge. Neurological follow up of the infants was not addressed.

REVIEWERS' CONCLUSIONS

The role of maintenance therapy with calcium channel blockers for preventing preterm birth is not clear. Well designed randomised trials of sufficient size with relevant outcomes are required.