First trimester amniocentesis between the seventh and 13th weeks: evaluation of the earliest possible genetic...

Amniocentesis performed at the 12th week and later gives reliable results. The procedure can be performed using regimens developed for mid-trimester amniotic fluid (AF) cells. Extension to the 10th-11th week is, in principle, feasible. However, the high cytogenetic failure rate is a difficulty and despite a high clone count, the culture time is prolonged. The problem of the relatively high loss of AF could be overcome by cell filtration techniques and replacement of the fluid. Because of the short turnover rate of the AF, this may be unnecessary or replacement with an isotonic solution may be sufficient. (Pseudo)mosaicism appears to occur more frequently in early than in late amniocentesis. As yet, data are too sparse to allow a comparison with chorionic villus sampling. There are no reliable follow-up data from which to estimate the abortion rate and the number of embryonic malformations.