Cervical assessment by ultrasound for preventing preterm delivery

 

Abstract

Background

Measurement of cervical length (CL) by transvaginal ultrasound (TVU) is predictive of preterm birth (PTB). It is unclear if this screening test is effective for prevention of PTB.

Objectives

To assess the effectiveness of antenatal management based on TVU CL screening for preventing PTB.

Search methods

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (September 2008), MEDLINE (1966 to September 2008), and reviewed the reference list of all articles. We updated the search of the Cochrane Pregnancy and Childbirth Group's Trials Register on 27 January 2012 and added the results to the awaiting classification section.

Selection criteria

Published and unpublished randomized controlled trials including pregnant women between the gestational ages of 14 to 32 weeks screened with TVU CL for risk of PTB. This review focuses exclusively on studies based on knowledge versus no knowledge of TVU CL results.

Data collection and analysis

All potential studies identified as in the search were assessed for inclusion by three independent review authors. We also analyzed studies for quality measures and extracted data.

Main results

Of 12 trials identified, five were eligible for inclusion (n = 507). Three included singleton gestations with preterm labor (PTL); one included singleton gestations with preterm prelabour rupture of membranes (PPROM); and one included twin gestations without or with PTL.

In the three trials of singleton gestations with PTL, 290 women were randomized; 147 to knowledge and 143 to no knowledge of TVU CL. Knowledge of TVU CL results was associated with a non-significant decrease in PTB at less than 37 weeks (22.3% versus 34.7%, respectively; risk ratio 0.59, 95% confidence interval (CI) 0.26 to 1.32). Delivery occurred at a later gestational age in the knowledge versus no knowlege groups (mean difference 0.64 weeks (CI 0.03 to 1.25)). All other outcomes for which there were available data (PTB at less than 34 or 28 weeks; birthweight less than 2500 grams; perinatal death; maternal hospitalization; tocolysis; and steroids for fetal lung maturity) were similar in the two groups.

The trial of singleton gestations with PPROM (n = 92) evaluated as its primary outcome safety of TVU CL in this population, and not its effect on management. The incidence of maternal and neonatal infections was similar in the TVU CL and no TVU CL groups.

In the trial of twin gestations with or without PTL (n = 125), PTB at less than 36, 34, or 30 weeks, gestational age at delivery, and other perinatal and maternal outcomes were similar in the TVU CL and the no TVU CL groups. Life table analysis revealed significantly less preterm birth at less than 35 weeks in the TVU CL group compared to the no TVU CL group (P = 0.02).

Authors' conclusions

Currently there is insufficient evidence to recommend routine screening of asymptomatic or symptomatic pregnant women with TVU CL. Since there is a non-significant association between knowledge of TVU CL results and a lower incidence of PTB at less than 37 weeks in symptomatic women, we encourage further research. Future studies should look at specific populations separately (eg singleton versus twins; symptoms of PTL or no such symptoms), report on all pertinent maternal and perinatal outcomes, and include cost-effectiveness analyses. Most importantly, future studies should include a clear protocol for management of women based on TVU CL results, so that it can be easily evaluated and replicated.

[Note: The two citations in the awaiting classification section of the review may alter the conclusions of the review once assessed.]

 

Plain language summary

Cervical assessment by ultrasound for preventing preterm delivery

Preterm birth before 37 weeks is the main cause of death and disability for neonates. The lower part of the uterus, called the cervix, is the passage through which births, including preterm, occur. Ultrasound performed through the vagina can detect early changes of the cervix that predict preterm birth. This review assessed if knowledge of such changes can prevent preterm birth. Of the 12 trials identified, five (507 women) were eligible for inclusion. Currently the studies reported are insufficient to recommend ultrasound of the cervix for prevention of preterm birth. Since there is a tendency for knowledge of the results of the cervical ultrasound to be associated with a lower chance of preterm birth in women who have uterine contractions and preterm labor, further research should be encouraged.

 

摘要

背景

使用超音波評估子宮頸以預防早產

藉由經陰道超音波(transvaginal ultrasound (TVU))測量子宮頸長度(cervical length (CL))可以用來預測早產(preterm birth (PTB))，還不清楚這種篩檢方式是否有助於預防早產。

目標

評估產前根據陰道超音波測量子宮頸長度來預防早產的效果。

搜尋策略

我們搜尋Cochrane Pregnancy和Childbirth Group's Trials Register (2008年9月)、MEDLINE (1966年2008年9月)、回顧所有文獻的參考資料。

選擇標準

納入妊娠14 – 32週、使用陰道超音波測量子宮頸長度，評估早產風險的已發表和未發表之隨機控制試驗(randomized controlled trials)。本回顧著重探討醫療者是否知道經陰道超音波測量之子宮頸長度對預防早產的影響。

資料收集與分析

由3位回顧作者獨立評估納入的研究，我們也分析研究測量方法的品質以及摘錄資料。

主要結論

檢視的12篇試驗中，有5篇被納入((n = 507)。其中3篇試驗中的孕婦為單胎妊娠併早產(PTL)；1篇試驗中的孕婦為單胎妊娠併早產之早期破水 (PPROM)； 1篇試驗中的孕婦為雙胞胎妊娠有或沒有早產。 篇針對為單胎妊娠併早產孕婦的試驗中，290位孕婦被隨機分組，醫療者知道147名孕婦的經陰道超音波測量之子宮頸長度，不知道其它143名孕婦的子宮頸長度。知道陰道超音波測量之子宮頸長度數值與降低37週前早產風險並無顯著關係 (22.3% versus 34.7%, respectively; risk ratio 0.59, 95% confidence interval (CI) 0.26 to 1.32)，此組孕婦之生產週數相對對照組較晚 (mean difference 0.64 weeks (CI 0.03 to 1.25))，兩組的其他結果相似(如小於34週或28週的早產、出生體重低於2500gm、胎死腹中、母親住院日數、安胎日數、使用類固醇幫助胎兒肺部成熟)。 針對單胎併早產之早期破水孕婦的試驗 (n = 92)，是評估使用陰道超音波測量子宮頸長度的安全性，而不是評估測量數值對處置的影響，在有測量組與無測量組間母嬰的感染發生率相似。 有或無早產之雙胞胎妊娠的試驗(n = 125)中， 比較有測量組與無測量組，36、 34或 0週前早產、其它週產期及母親狀況的各項結果都相似。生命表分析發現相較無測量組，有測量組小於35週的早產有顯著減少(P = 0.02)。

作者結論

目前沒有足夠的證據建議使用陰道超音波測量子宮頸長度作為有症狀或無症狀孕婦的例行性篩檢。因為知道陰道超音波測量子宮頸長度與減少有症狀孕婦小於37週早產沒有顯著相關性。我們鼓勵後續的研究，可以對特定族群(例如單胎妊娠與雙胎妊娠比較，有早產症狀與無症狀比較)，報告週產期母嬰的結果，包括成本效益的分析。更重要的是，後續的研究應包括在測量陰道超音波測量子宮頸長度後的明確處置流程，以便評估和再現。

翻譯人

此翻譯計畫由臺灣國家衛生研究院(National Health Research Institutes, Taiwan)統籌。

總結

37週前的早產是新生兒死亡和失能的主因. ，子宮的下部即所謂的子宮頸，是足月及早產胎兒陰道生產必經之處。經陰道超音波測量子宮頸長度，可以早期發現子宮頸的變化用以預測早產。此篇回顧評估知道子宮頸長度的變化，是否能預防早產的發生。目前的研究還不足以建議使用陰道超音波測量子宮頸長度來預防早產。對於已有子宮收縮及早產徵兆的孕婦，知道陰道超音波測量子宮頸之長度有減少早產發生的傾向，但需要後續的進一步研究。