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A freehand ultrasonographically guided technique in transabdominal chorionic villus sampling in more than 24 000 consecutive cases

We read with a great deal of interest the article by Calda and Brestak about chorionic villus vacu-sampling using the Vacutainer system (Calda and Brestak, 2009). We take this opportunity to reply to the authors as the published technique and the results obtained were not in agreement with our own practical experience. Since 1983, in our prenatal diagnostic center we have carried out chorionic villus sampling on more than 24 000 women using first the transcervical route and then the transabdominal route. The transcervical route was used from 1983 to 1988, but we then abandoned this method because of a very high rate of miscarriages linked with the procedure (∼4%). Since 1988, we have carried out transabdominal chorionic villus sampling exclusively, using the same technique between the 12th and the 37th week of amenorrhea. The technique we use is based on that described by Smidt-Jensen and Hahnemann (1984). It consists of an extra-amniotic transabdominal chorionic villus sampling puncture, monitored with ultrasound, using a 20-gauge needle rinsed with heparin serum then linked to a 20mL syringe by a plastic extension tube (Saura et al., 1992). The rate of miscarriage when using the 20-gauge needle in our medical fetal center is the same as for amniocentesis (Brun et al., 2003). Our first point is that the 20-gauge needle we use for chorionic villus sampling causes no more pain than amniocentesis, and therefore has the advantage of not requiring a local anesthetic prior to the chorionic villus puncture, which is necessary with an 18-gauge needle (Calda and Brestak, 2009; Vandenbossche et al., 2007). Next, we stress the importance of the quantity of chorionic villi sampled. It is the quantity of chorionic villi fragments that will determine the culture time, and thus ultimately, the advantage of using the chorionic villus sampling method. The smaller this quantity, the longer it takes to obtain conventional karyotyping of the culture. It may take up to 15–20 days, or even longer, if the quantity sampled is less than 5 mg, as reported by the authors. In this case, the advantage to be obtained from chorionic villus sampling is very much reduced and the benefits of choriocentesis over amniocentesis become debatable. Thus, the threshold amount of chorionic villi that is sufficient, and which the authors set at 5 mg, seems to us to be completely inadequate. We believe that a large amount of chorionic material should be sampled (more than 15–20 mg) mainly in order to obtain the conventional karyotype after 6–8 days culture. In our opinion, it is essential to obtain about 15–20 mg of chorionic villi in order to: