{'fraction_non_alphanumeric': 0.025848142164781908, 'fraction_numerical': 0.022617124394184167, 'mean_word_length': 4.961538461538462, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Chorionic villi sampling under direct vision

Ultrasound-guided aspiration, the technique most commonly used for chorionic villi sampling, involves the trans-cervical insertion of a 1.5 mm diameter soft polyethylene catheter mounted on a flexible aluminium obturator (Ward et al. 1983, Simoni et al. 1983). The catheter is advanced towards the site of the placenta under ultrasound guidance. The obturator is then withdrawn, a 20 ml syringe is attached to the catheter, and about 10 ml of suction applied. One disadvantage of this method is that the sample obtained may be contaminated with maternal decidual fragments.