title: Instruments for chorionic villus sampling for prenatal diagnosis.
abstract: BACKGROUND
  Chorionic villus sampling (CVS) is the method of choice for obtaining fetal tissue for prenatal diagnosis before 15 weeks of pregnancy. CVS can be performed using either transabdominal or transcervical approach. The type of instrument used 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 instruments used to obtain chorionic tissue in early pregnancy by transabdominal or transcervical route (chorionic villus sampling). The outcomes of interest were technical difficulties during the procedure, quality and quantity of obtained tissue, maternal adverse effects, pregnancy outcome and cost-effectiveness.
  
  
  METHODS
  The Cochrane Pregnancy and Childbirth Group trials register was searched. Date of last search: November 2002.
  
  
  METHODS
  Randomised trials comparing different instruments (forceps, cannula, needle) for chorionic villus sampling using either transabdominal or transcervical approach.
  
  
  METHODS
  Eligibility and trial quality were assessed by two reviewers.
  
  
  RESULTS
  There were no trials comparing instruments for transabdominal CVS. Forceps and cannula were evaluated in five transcervical CVS trials involving 472 women. When a cannula was used, operators obtained an inadequate sample (less than 5 mg) more often (relative risk (RR) 4.21, 95% confidence interval (CI) 2.15 to 8.25). Compared with forceps, cannulae had to be re-inserted more often (RR 2.98, 95% CI 1.62 to 5.47). Also, inserting a cannula was more painful (RR 1.93, 95% CI 1.11 to 3.37). One study reported the cost of the procedures and found CVS with cannula to be more expensive (weighted mean difference $183.7, 95% confidence interval 152.62 to 214.78). When different types of cannulae were compared, Portex cannula was more likely to result in an inadequate sample and a difficult or painful procedure when compared with either the silver or aluminum cannula respectively.
  
  
  CONCLUSIONS
  Although there is some evidence to support the use of small forceps for transcervical chorionic villus sampling, the evidence is not strong enough to support change in practice for clinicians who have become familiar with aspiration cannulae.
authors.affiliation: Department of Obstetrics and Gynaecology, University of Liverpool, Liverpool, UK, L69 3BX. zarko@liverpool.ac.uk
authors.forename: Z
authors.initials: Z
authors.lastname: Alfirevic
authors.forename: P
authors.initials: P
authors.lastname: von Dadelszen
mesh_terms: D015193:Chorionic Villi Sampling / Q000295:instrumentation*; D005260:Female; D006801:Humans; D011247:Pregnancy; D013396:Suction / Q000295:instrumentation; D013525:Surgical Instruments