In this retrospective analysis we studied 1489 women who underwent prenatal invasive diagnostic procedures between January 2000 and December 2002. We examine the influence of risk factors and the incidence of early complications following amniocentesis and chorion villus sampling, in particular the incidence of fetal loss. The study group included 438 women who underwent CVS and 1051 underwent amniocentesis. For each woman we studied anamnestic risk factors (recurrent pregnancy losses, fibroids, twin birth, uterine hematic loss), intraoperative risk factors (repetition of the insertion, transplacental sample, hematic liquid, early bleeding) and postoperative risk factors (pelvic pain, hematic losses, liquid losses, spastic pain, fever). In our data the miscarriage incidence was 1% for CVS and 1.7% for amniocentesis. Our results showed that in relation to CVS, the presence of fibroids gives an OR of miscarriage of 68 (95% C.I.=6.50-659.78; p=0.000). In relation to amniocentesis, the incidence of hematic losses gives an OR of miscarriage of 10 (95% C.I.=1.50-32.94; p=0.04). If these results were confirmed by other experiences, they could induce obstetricians to avoid CVS in these women with uterine fibroids and hence recommend amniocentesis to them. Particular attention has to be taken in those patients with vaginal bleeding following amniocentesis.