Amniocentesis and chorionic villus sampling for prenatal diagnosis
Evidence Summaries Level of Evidence = A
Second trimester amniocentesis increases the risk of spontaneous miscarriage but is safer than transcervical chorionic villus sampling and early amniocentesis.
A Cochrane review 1 included 16 studies. Spontaneous miscarriages are more common following second trimester amniocentesis as compared with controls with no amniocentesis (2.1% vs. 1.3%; RR 1.02–2.52). Early amniocentesis is not a safe early alternative to second trimester amniocentesis because of increased pregnancy loss (7.6% vs. 5.9%; RR 1.29, 95% CI 1.03–1.61) and higher incidence of talipes compared to CVS (chorionic villus sampling) (RR 4.61; 95% CI 1.82 to 11.66).
Compared with second trimester amniocentesis, transcervical CVS carries a significantly higher risk of pregnancy loss (14.5% versus 11%; RR 1.40, 95% CI 1.09 to 1.81) and spontaneous miscarriage (12.9% versus 9.4%; RR 1.50, 95% CI 1.07 to 2.11). One study compared transabdominal CVS with second trimester amniocentesis and found no significant difference in the total pregnancy loss between the two procedures (6.3% versus 7%). Transcervical CVS is more technically demanding than transabdominal CVS with more failures to obtain sample and more multiple insertions.
1. Alfirevic Z, Sundberg K, Brigham S. Amniocentesis and chorionic villus sampling for prenatal diagnosis. Cochrane Database Syst Rev 2003;(3):CD003252 (Last assessed as up-to-date: 28 June 2008). [PMID:12917956]
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