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Amniocentesis and Chorionic Villus Sampling (Green-top Guideline No. 8)

Published: 23/06/2010

Update February 2017: Please note, following a review of the guidelines in December 2016, minor amendments have been made. The version available here is the most up to date. The date on the guideline has not been changed since no amendments were made to the content.


Update December 2014: New evidence and guidance in this field were reviewed in 2014 and it was decided that revision of this guideline would be deferred to a later date. The version available on the website and app will remain valid until replaced.


This is the fourth edition of this guideline, which was previously published in October 1996, February 2000 and January 2005.


It is estimated that around 5% of the pregnant population (approximately 30,000 women per annum in the UK) are offered a choice of invasive prenatal diagnostic tests, most commonly amniocentesis or chorionic villus sampling (CVS). The type of diagnostic test available and offered is likely to vary depending upon the timing of any initial screening test that is performed. 

Amniocentesis is the most common invasive prenatal diagnostic procedure undertaken in the UK. Most amniocenteses are performed to obtain amniotic fluid for karyotyping from 15 weeks (15+0 ) onwards. Amniocentesis performed before 15 completed weeks of gestation is referred to as ‘early amniocentesis’.

CVS is usually performed between 11 (11+0 ) and 13 (13+6 ) weeks of gestation and involves aspiration or biopsy of placental villi. CVS can be performed using either a transabdominal or a transcervical approach.

This guideline sets out a series of evidence-based standards for provision of amniocentesis and CVS.