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

Published: 25 October 2021

Summary

Pregnant women are offered amniocentesis or chorionic villus sampling (CVS) for prenatal diagnosis for a variety of reasons including a higher chance aneuploidy screening result, fetal structural anomaly, or a known risk of inherited genetic disease.

CVS is usually performed between 11⁺⁰ and 13⁺⁶ weeks of gestation. If required, CVS can be performed between 14⁺⁰ and 14⁺⁶ weeks’ gestation. Individualised counselling of the merits of CVS versus amniocentesis should be provided for women considering CVS during this time period. Amniocentesis, performed to obtain amniotic fluid for analysis, is usually offered from 15⁺⁰ weeks.

COVID disclaimer

This guideline was developed as part of the regular programme of Green-top Guidelines, as outlined in our document Developing a Green-top Guideline: Guidance for developers (PDF), and prior to the emergence of COVID-19.

Version history

This is the fifth edition of this guideline.

Please note that the information provided in this update will be considered for update by the RCOG Guidelines Committee 3 years after publication, with an intermediate assessment of the need to update 2 years after publication.

Developer declaration of interests

Dr K Navaratnam: None declared
Professor Z Alfirevic: None declared.

Key points

• Women should be informed that the additional risk of miscarriage following amniocentesis or CVS performed by a skilled operator is likely to be below 0.5%.
•  Amniocentesis should not be performed prior to 15⁺⁰ weeks gestation.CVS should be performed between 11⁺⁰ and 13⁺⁶ weeks; it should not be performed prior to 10⁺⁰ weeks gestation.