Genetic amniocentesis: gestation-specific pregnancy outcome and comparison of outcome following early and traditional amniocentesis

Abstract

Amniocentesis remains the most common prenatal diagnostic invasive procedure for fetal karyotyping. During counselling prior to this procedure miscarriage rates are often quoted as a single figure. In this review of 2924 amniocenteses, we report that miscarriage rates vary with the gestational age at which the procedure is performed. The total miscarriage rate was 1.0 per cent after early amniocenteses (11 + 0-14 + 6 weeks) and 1.2 per cent after traditional mid-trimester amniocenteses (15 + 0-18 + 6 weeks). The rate was greatest (3.1 per cent) for amniocenteses performed after 18 + 6 weeks' gestation. The cumulative miscarriage risk increased from 0.03 per cent one week after the procedure to plateau at 1.1 per cent five weeks after the procedure. The preterm and still-birth rates following amniocenteses were similar in early and traditional mid-trimester amniocenteses but were significantly higher when amniocenteses were performed after 19 weeks' gestation. Although the incidence of talipes equinovarus was higher after early amniocentesis compared with traditional mid-trimester amniocenteses (1.4 per cent versus 0.2 per cent), none of the affected infants required corrective surgery. We conclude that counselling for this procedure should be tailored to each unit's unintended fetal loss rate based on cumulative rates. Such figures should be available to parents to assist them in their decision-making.