J Cochrane Database Syst Rev. 2005 Jul 20;(3):CD004733.
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Prophylactic oral betamimetics for reducing preterm
birth in women with a twin pregnancy.
Yamasmit W, Chaithongwongwatthana S, Tolosa JE,
Limpongsanurak S, Pereira L, Lumbiganon P.
Department of Obstetrics and Gynaecology, Bangkok
Metropolitan Administration Medical College and Vajira
Hospital, Samsen Road, Dusit, Bangkok, Thailand, 10300.
iammammy@hotmail.com
Background:
Twin pregnancies are associated with a high
risk of neonatal mortality and morbidity due to an
increased rate of preterm birth. Betamimetics can
decrease contraction frequency or delay preterm birth in
singleton pregnancies by 24 to 48 hours. The efficacy of
oral betamimetics in women with a twin pregnancy is
unproven.
Objectives:
To assess the effects of
prophylactic oral betamimetics administered to women
with twin pregnancies.
Search Strategy:
We searched the
Cochrane Pregnancy and Childbirth Group Trials Register
(May 2004), CENTRAL (The Cochrane Library, Issue 2,
2004), MEDLINE (January 1966 to May 2004), EMBASE
(January 1985 to May 2004), and reference lists.
Selection Criteria:
Randomized controlled trials in twin
pregnancies comparing oral betamimetics with placebo or
any intervention with the specific aim of preventing
preterm birth. DATA COLLECTION AND ANALYSIS: Standard
methods of The Cochrane Collaboration and the Cochrane
Pregnancy and Childbirth Group were used. Trials were
independently assessed for methodological quality by at
least two authors, who extracted data using a data
collection form.
Main Results:
Five trials (344 twin
pregnancies) were included. All trials compared oral
betamimetics to placebo. Betamimetics reduced the
incidence of preterm labour (one trial, 50 twin
pregnancies, relative risk (RR) 0.40; 95% confidence
interval (CI) 0.19 to 0.86). However, betamimetics did
not reduce preterm birth less than 37 weeks' gestation
(four trials, 276 twin pregnancies, RR 0.85; 95% CI 0.65
to 1.10) or less than 34 weeks' gestation (one trial,
144 twin pregnancies, RR 0.47; 95% CI 0.15 to 1.50).
Mean neonatal birthweight in the betamimetic group was
significantly higher than in the placebo group (three
trials, 478 neonates, weighted mean difference 111.2
grams; 95% CI 22.2 to 200.2). Nevertheless, there was no
evidence of an effect of betamimetics in reduction of
low birthweight (two trials, 366 neonates, RR 1.19; 95%
CI 0.77 to 1.85) or small-for-gestational age neonates
(two trials, 178 neonates, RR 0.92; 95% CI 0.52 to
1.65). Two trials (388 neonates) showed that
betamimetics significantly reduced the incidence of
respiratory distress syndrome but the difference was not
significant when the analysis was adjusted for
correlation of babies from twins. Three trials (452
neonates) showed no evidence of an effect of
betamimetics in reducing neonatal mortality (RR 0.80;
95% CI 0.35 to 1.82). AUTHORS'
Conclusions:
There is
insufficient evidence to support or refute the use of
prophylactic oral betamimetics for preventing preterm
birth in women with a twin pregnancy.
