Instruments for transcervical chorionic villus sampling for prenatal diagnosis.

Background: The type of instrument used in chorion villus sampling could have a significant impact on the success rate of the procedure. An ability to manoeuvre the instrument within the uterine cavity without puncturing the gestational sac, and to see the tip of the instrument on ultrasound scanning are particularly important.

Objective: The objective of this review was to assess the effects of different instruments for transcervical chorionic villus sampling on perinatal outcome, quality and quantity of obtained tissue, technical difficulties during the procedure and maternal adverse effects.

Methods: The Cochrane Pregnancy and Childbirth Group trials register was searched. Date of last search: October 1998. Methods: Randomised trials comparing different instruments for transcervical chorionic villus sampling. Methods: Eligibility and trial quality were assessed by one reviewer.

Results: Three trials involving 268 women were included. None of the trials mentioned method of randomisation. An adequate sample was more likely to be obtained using small forceps than aspiration cannula (odds ratio 7.29, 95% confidence interval 3. 39 to 15.67). However small forceps were more difficult to insert than an aspiration cannula (odds ratio 0.35, 95% confidence interval 0.13 to 0.96). Use of the Portex cannula was more likely to result in an inadequate sample and a difficult or painful procedure when compared with either the silver or aluminium cannula respectively.

Conclusions: Although there is some evidence to support the use of small forceps for transcervical chorionic villus sampling, it is not strong enough to support change in practice for clinicians who have become familiar with aspiration cannulas.