Amniocentesis in twin pregnancies: a systematic review of the literature

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Abstract
Objective Using published data, we sought to determine the amniocentesis-related loss rate in twin gestations. Methods We searched the PUBMED database using keywords amniocentesis, twin and twins to identify articles evaluating genetic amniocentesis in twin gestations published from January 1970 to December 2010. Random effects models were used to pool procedure-related loss rates from included studies. Results The definition of loss varied across the 17 studies identified (Table?1). The pooled procedure-related loss rate at?<?24?weeks was 3.5% (95% confidence interval [CI] 2.6-4.7) (Figure?2). Pooled loss rates at?<?28?weeks (Figure?4) and to term (Figure?5) could not be calculated due to unacceptable heterogeneity of available data. Seven studies included a control (no amniocentesis) group and reported a pooled odds ratio for total pregnancy loss among cases of 1.8 (95% CI 1.2-2.7) (Figure?3). Only 1 study reported procedure-related loss rates by chorionicity (7.7% among monochorionics vs 1.4% among controls; p 0.02). Conclusion Analysis of published data demonstrated a pooled amniocentesis-related loss rate of 3.5% in twin gestations?<?24?weeks. Pooled loss rates within other post-amniocentesis intervals or other gestational age windows and the impact of chorionicity on procedure-related loss rates cannot be determined from published data. (c) 2011 John Wiley & Sons, Ltd.