Congenital talipes and hip malformation in relation to amniocentesis: a case-control study.

A case-control study on 1342 infants was carried out to investigate whether mid-trimester amniocentesis might be a cause of congenital talipes or hip malformation. There was no evidence of any excess risk of having an infant with either of these malformations in mothers who had an amniocentesis; the estimate of relative risk in association with amniocentesis before 28 weeks of pregnancy was 1.08 (95% confidence interval, 0.7-1.6). There was no evidence that amniocentesis increased the risk of forms of these malformations that were sufficiently severe to require strapping, splintage, or surgery (relative risk 0.75, 95% confidence interval 0.4-1.4). Although there was no statistically significant association between amniocentesis and milder forms of these malformations (those requiring either no treatment or simple treatment by double nappies, physiotherapy, or manipulation), there is less confidence about the absence of an association (relative risk 1.32, 95% confidence interval 0.8-2.2).