Example of a Cochrane review

Example of a Cochrane review

The original version of this review, when first published in structured form in 1989, was the basis for the Cochrane logo. Cochrane Reviews are regularly checked to ensure that they remain up to date, and this latest version was published in The Cochrane Library in July 2006.The full text of this and other Cochrane Reviews are available in (ISSN 1464-780X).

Antenatal corticosteroids for accelerating fetal lung maturation for women at risk of preterm birth

Roberts D, Dalziel S

Cochrane Database of Systematic Reviews 2006 Issue 3. Copyright © 2006 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.

Abstract

Background:Respiratory distress syndrome (RDS) is a serious complication of preterm birth and the primary cause of early neonatal mortality and disability.

Objectives: To assess the effects on fetal and neonatal morbidity and mortality, on maternal mortality and morbidity, and on the child in later life of administering corticosteroids to the mother before anticipated preterm birth.

Search strategy: We searched the Cochrane Pregnancy and Childbirth Group Trials Register (30 October 2005).

Selection criteria: Randomised controlled comparisons of antenatal corticosteroid administration (betamethasone, dexamethasone, or hydrocortisone) with placebo or with no treatment given to women with a singleton or multiple pregnancy, expected to deliver preterm as a result of either spontaneous preterm labour, preterm prelabour rupture of the membranes or elective preterm delivery.

Data collection and analysis: Two review authors assessed trial quality and extracted data independently.

Main results: Twenty-one studies (3885 women and 4269 infants) are included. Treatment with antenatal corticosteroids does not increase risk to the mother of death, chorioamnionitis or puerperal sepsis. Treatment with antenatal corticosteroids is associated with an overall reduction in neonatal death (relative risk (RR) 0.69, 95% confidence interval (CI) 0.58 to 0.81, 18 studies, 3956 infants), RDS (RR 0.66, 95% CI 0.59 to 0.73, 21 studies, 4038 infants), cerebroventricular haemorrhage (RR 0.54, 95% CI 0.43 to 0.69, 13 studies, 2872 infants), necrotising enterocolitis (RR 0.46, 95% CI 0.29 to 0.74, eight studies, 1675 infants), respiratory support, intensive care admissions (RR 0.80, 95% CI 0.65 to 0.99, two studies, 277 infants) and systemic

infections in the first 48 hours of life (RR 0.56, 95% CI 0.38 to 0.85, five studies, 1319 infants). Antenatal corticosteroid use is effective in women with premature rupture of membranes and pregnancy related hypertension syndromes.

Conclusions: The evidence from this new review supports the continued use of a single course of antenatal corticosteroids to accelerate fetal lung maturation in women at risk of preterm birth. A single course of antenatal corticosteroids should be considered routine for preterm delivery with few exceptions. Further information is required concerning optimal dose to delivery interval, optimal corticosteroid to use, effects in multiple pregnancies, and to confirm the long-term effects into adulthood.

top of page Plain language summary

Corticosteroids given to women in early labour help the babies' lungs to mature and so reduce the number of babies who die or suffer breathing problems at birth

Babies born very early are at risk of breathing difficulties (respiratory distress syndrome) and other complications at birth. Some babies have developmental delay and some do not survive the initial complications. In animal studies, corticosteroids are shown to help the lungs to mature and so it was suggested these drugs may help babies in preterm labour too. This review of 21 trials shows that a single course of corticosteroid, given to the mother in preterm labour and before the baby is born, helps to develop the baby's lungs and reduces complications like respiratory distress syndrome. Furthermore, this treatment results in fewer babies dying and fewer common serious neurological and abdominal problems, e.g. cerebroventricular haemorrhage and necrotising enterocolitis, that affect babies born very early. There does not appear to be any negative effects of the corticosteroid on the mother. Long-term outcomes on both baby and mother are also good. top of page

Background

Respiratory distress syndrome (RDS) is a serious complication of preterm birth and the primary cause of early neonatal death and disability. It affects up to one fifth of low birthweight babies (less than 2500 g) and two thirds of extremely low birthweight babies (less than 1500 g).

Respiratory failure in these infants occurs as a result of surfactant deficiency, poor lung anatomical development and immaturity in other organs. Neonatal survival after preterm birth improves with gestation (), reflecting improved maturity of organ systems. However, those who survive early neonatal care are at increased risk of long-term neurological disability ().

History

While researching the effects of the steroid dexamethasone on premature parturition in fetal sheep in 1969, Liggins found that there was some inflation of the lungs of lambs born at gestations at which the lungs would be expected to be airless (). He theorised, from these observations, that dexamethasone might have accelerated the appearance of pulmonary surfactant. The hypothesis is that corticosteroids act to trigger the synthesis of ribonucleic acid that codes for particular proteins involved in the biosynthesis of phospholipids or in the breakdown of glycogen. Subsequent work has suggested that, in animal models, corticosteroids mature a number of organ systems (; ). Liggins and Howie performed the first randomised controlled trial in humans of betamethasone for the prevention of RDS in 1972 ().

Fetal lung development

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