title: Early amniocentesis versus transabdominal chorion villus sampling for prenatal diagnosis.
abstract: BACKGROUND
  A major disadvantage of amniocentesis is that test results are usually available only after 18 weeks gestation. Early amniocentesis can now be done between 9 to 14 weeks gestation.
  
  
  OBJECTIVE
  The objective was to assess the safety and accuracy of early amniocentesis compared with chorion villus sampling.
  
  
  METHODS
  The Cochrane Pregnancy and Childbirth Group trials register and the Cochrane Controlled Trials Register were searched. Date of last search: October 1998.
  
  
  METHODS
  Randomised trials comparing early amniocentesis with transabdominal chorion villus sampling.
  
  
  METHODS
  One reviewer assessed eligibility and trial quality.
  
  
  RESULTS
  Three studies were included. Sampling failure was 0.4% in the early amniocentesis group compared to 2% in the chorion villus group (relative risk 0.23, 95% confidence interval 0.08 to 0.65). Consequently, more women in the chorion villus sampling group needed a second prenatal diagnostic test (relative risk 0.43, 95% confidence interval 0.21 to 0.88). There were no statistically significant differences in the laboratory failures (relative risk 0.43, 95% confidence interval 0. 17 to 1.10) or number of women with various chromosomal abnormalities (relative risk 0.51, 95% confidence interval 0.26 to 1. 04). Combined total pregnancy loss in the early amniocentesis group was 6.2% (57/915) compared with 5% (46/917) in the chorion villus sampling group (relative risk 1.24, 95% confidence interval 0.85 to 1.81). There were more spontaneous miscarriages after early amniocentesis (4.4% versus 2.3%, relative risk 1.92, 95% confidence interval 1.14 to 3.23). There was no difference in the incidence of neonatal respiratory distress and anomalies in the newborn infants. The incidence of talipes was greater in the early amniocentesis group, although haemangiomas were more common in the chorion villus sampling group.
  
  
  CONCLUSIONS
  Current data suggest that early amniocentesis is associated with a greater risk of spontaneous miscarriage and neonatal talipes compared to transabdominal chorion villus sampling. An increased risk of these complications needs to be weighed against fewer technical difficulties and the possibility of fewer neonatal haemangiomas.
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
mesh_terms: D000649:Amniocentesis; D015193:Chorionic Villi Sampling; D005260:Female; D006801:Humans; D011247:Pregnancy; D016032:Randomized Controlled Trials as Topic