Early genetic amniocentesis and chorionic villus sampling. Expanding the opportunities for early prenatal diagnosis.

At centers where chorionic villus sampling (CVS) programs are operational, first-trimester prenatal diagnosis has been shown to have many advantages, both medical and psychologic. However, most medical centers do not have CVS capability, nor are all patients candidates for CVS. We investigated the feasibility of performing very early genetic amniocentesis (9-13 weeks' gestational age). The results from those amniocenteses were compared to our own CVS data. In experienced hands, (1) CVS can be performed safely at 8-13 weeks, with the most technical ease at 9-11 weeks; (2) CVS or amniocentesis can be performed on many patients at 12-13 weeks or perhaps even earlier, although no accurate loss rates are available yet; (3) when technically feasible, CVS may be advantageous because of the much faster time period for cytogenetic results from direct preparation or short-term culture; and (4) in those patients on whom CVS cannot be performed, early amniocentesis in selected patients may offer the benefits of early diagnosis.