{'fraction_non_alphanumeric': 0.023944549464398234, 'fraction_numerical': 0.0, 'mean_word_length': 5.377510040160643, '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}}
Antenatal screening for Down's syndrome in assisted reproductive pregnancies.

The wide use of assisted conception methods has risen dramatically. The greater proportion of singletons, twins and high order of multiplicity conceived by those methods have already focused the medical community to various obstetric complications. Recently, there have been suggestions that the levels of mid-gestation serum markers, particularly human chorionic gonadotrophin (HCG), might be affected by assisted conception, leading to higher false-positive results. Furthermore, women who conceived after assisted reproduction methods are on average older, and in many cases their current pregnancy was achieved after long-standing infertility and might even be their last one. This is why they are extremely wary of any invasive fetal karyotyping. Therefore, every effort should be made to provide them with the most accurate screening of Down's syndrome (DS) risk. In this respect, nuchal translucency (NT) measurement, which has been reported to be another effective screening method, might be a more reliable marker in these pregnancies. This review explores the problematic issue of antenatal DS screening in assisted conception pregnancies. For the singletons and twins, a sequential NT and second-trimester serum marker screening can be offered, thus producing a single risk estimation which seems to be more accurate. For the high order of multiplicity, the NT offers additional important data, which can be taken in consideration both as a screening tool for DS and if fetal reduction is planned.