Amniocentesis and chorionic villus sampling for prenatal diagnosis

 

Abstract

Background

A major disadvantage of second trimester amniocentesis is that the results are available relatively late in pregnancy (after 16 weeks' gestation). Chorionic villus sampling (CVS) and early amniocentesis can be done in the first trimester of pregnancy and offer an earlier alternative.

Objectives

To assess comparative safety and accuracy of second trimester amniocentesis, early amniocentesis, transcervical and transabdominal CVS.

Search methods

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (January 2008).

Selection criteria

All randomised trials comparing amniocentesis and CVS by either transabdominal or transcervical route.

Data collection and analysis

Two review authors independently assessed eligibility and trial quality and performed data extraction.

Main results

We included a total of 16 randomised studies.

One study in a low-risk population (N = 4606) with a background pregnancy loss of around 2% found that a second trimester amniocentesis will increase total pregnancy loss by another 1%. This difference did not reach statistical significance and the confidence intervals (CI) around this excess risk were relatively large (risk ratio (RR) 1.41; 95% CI 0.99 to 2.00). In the same study, compared with no intervention, the increase in spontaneous miscarriages following second trimester amniocentesis was statistically significant (2.1% versus 1.3%; RR 1.60; 95% CI 1.02 to 2.52).

Early amniocentesis is not a safe early alternative to second trimester amniocentesis because of increased pregnancy loss (7.6% versus 5.9%; RR 1.29; 95% CI 1.03 to 1.61) and higher incidence of talipes compared to CVS (RR 4.61; 95% CI 1.82 to 11.66).

Compared with a second trimester amniocentesis, transcervical CVS carries a higher risk of pregnancy loss, although the results are quite heterogeneous. One study compared transabdominal CVS with second trimester amniocentesis and found no significant difference in the total pregnancy loss between the two procedures.

Transcervical CVS is more technically demanding than transabdominal CVS, with more failures to obtain sample and more multiple insertions. However, the results related to comparative pregnancy loss between transabdominal and transcervical CVS are inconclusive, with significant heterogeneity between studies.

Authors' conclusions

Second trimester amniocentesis is safer than early amniocentesis or transcervical CVS, and is the procedure of choice for second trimester testing. Transabdominal CVS should be regarded as the procedure of first choice when testing is done before 15 weeks' gestation. Diagnostic accuracy of different methods could not be assessed adequately because of incomplete karyotype data in most studies.

 

Plain language summary

Amniocentesis and placental sampling for pre-birth diagnosis

Many women want to be reassured that their unborn baby is healthy. It is important that screening and diagnostic tests used are accurate and safe and can be done early enough in pregnancy to allow them the choice of terminating the pregnancy. Second trimester amniocentesis is most often used, at around 16 weeks' gestation. A needle is inserted through the abdominal wall into the uterus to remove amniotic fluid. Early amniocentesis or chorionic villus sampling (CVS) to withdraw placental tissue can be done  before 15 weeks. Either a transabdominal or vaginal (transcervical) approach is used for CVS.

We identified a total of 16 randomised controlled trials for the review. One study of 4606 women in a low-risk population found that a second trimester amniocentesis increased spontaneous miscarriages, 2.1% versus 1.3% with no intervention.

Early amniocentesis was not a safe early alternative to second trimester amniocentesis because of increased pregnancy loss and a higher incidence of deformed or club foot (talipes). It is also technically more demanding and involves a greater number of needle insertions, laboratory failures and false negative results.

Transcervical CVS also increased the risk of total pregnancy compared with a second trimester amniocentesis, mostly because of spontaneous miscarriages. Transabdominal CVS may be safer than the transcervical route, but the data are limited. Transcervical CVS is also more technically demanding than transabdominal CVS, with more failures to obtain sample and more multiple needle insertions required. It is more likely to cause vaginal bleeding immediately after the procedure, in approximately 10% of women.

 

摘要

背景

羊膜穿刺和絨膜絨毛取樣用於產前診斷

懷孕第2期進行羊膜穿刺(amniocentesis)的主要不利之處是，結果通常在妊娠18週之後才可得知。可以在9 – 14週進行絨膜絨毛取樣(Chorionic villus sampling (CVS)、或提早進行羊膜穿刺，來提供較早的替代方法

目標

目標是比較懷孕第2期羊膜穿刺、提早進行羊膜穿刺、及經子宮頸和經腹部CVS之安全性和準確性

搜尋策略

我們搜尋Cochrane Pregnancy和Childbirth Group trials register (March 2003)與Cochrane Central Register of Controlled Trials (The Cochrane Library, Issue 1, 2002)

選擇標準

所有的隨機試驗都是要比較羊膜穿刺和絨膜絨毛取樣

資料收集與分析

2位回顧者評估適用性與試驗品質，進行資料摘錄。我們使用RevMan軟體分析資料

主要結論

總共納入14篇隨機研究。低風險族群的背景流產率約為2% ，懷孕第2期羊膜穿刺使此一風險增加約1% ，但此差異未達統計上的顯著意義，然而，懷孕第2期羊膜穿刺後，自發性流產比控制組(無羊膜穿刺)增加(2.1% 相較於1.3% ；RR為1.02 – 2.52)。提早羊膜穿刺不是一個可以替代懷孕第2期羊膜穿刺的安全方法，因為它會增加流產率(7.6% 相較於5.9% R為 1.29, 95% CI為1.03 −1.61)，且畸形腳的發生率比CVS高(1.8% 相較於0.2% R為 6.43, 95% CI為 1.68 −24.64)。相較於懷孕第2期羊膜穿刺，經子宮頸CVS的流產率風險顯著較高(14.5% 相較於11% R為 1.40, 95% CI為 1.09 – 1.81)，自發性流產率也較高(12.9% 相較於9.4% R為 1.50, 95% CI為 1.07 – 2.11)。有一篇研究比較經腹部CVS和懷孕第2期羊膜穿刺，發現兩者之間的整體流產率沒有顯著差異(6.3% 相較於7%)。經子宮頸CVS的技術需求高於經腹部CVS，取得樣本的失敗率較高而需要較多次的穿刺

作者結論

懷孕第2期羊膜穿刺比起經子宮頸CVS和提早羊膜穿刺更加安全。如果需要及早診斷，經腹部CVS比提早羊膜穿刺或經子宮頸CVS更可行。如果進行經腹部CVS有技術上的困難時，可以在懷孕第1期進行經子宮頸CVS或懷孕第2期羊膜穿刺

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

羊膜穿刺在妊娠16週之後比較安全，絨膜絨毛取樣最好是透過子宮壁採樣。有些父母親希望確認他們的嬰兒先天良好，可以從羊水取樣(羊膜穿刺)或從胎盤取樣(絨膜絨毛取樣)後進行分析。本回顧之研究發現，對於不同的取樣方法，流產風險會因此而略為增加。在16 – 18週進行羊膜穿刺是最安全的。CVS可以早些進行(約10 – 13週)，而且相較於透過陰道和子宮頸，透過子宮壁取樣會對於嬰兒比較安全