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Over the last three decades, prenatal screening for Down syndrome and other chromosomal abnormalities has become routine during antenatal care. Down syndrome screening has changed from the second to the first trimester of pregnancy because of the higher detection rate and earlier diagnosis. Second-trimester screening, based on the combination of maternal serum human chorionic gonadotropin (hCG), alpha-fetoprotein (AFP), and unconjugated estradiol (uE3) as a function of maternal age, yields a detection rate of 60% with a falsepositive rate (FPR) of 5% (Wald et al., 1988). In standard practice, first-trimester screening, which combines maternal age, nuchal translucency thickness (NT), and maternal serum free beta-human chorionic gonadotropin (fβ-hCG), and pregnancy-associated plasma-protein-A (PAPP-A), can achieve a detection rate 90% with a FPR of 5% (Snijders et al., 1998; Nicolaides, 2004; Wojdemann et al., 2005; Spencer, 2007). Down syndrome screening among women pregnant after assisted reproductive technologies (ART) is complicated by several factors. Pregnancies conceived after ART represent a group of high-risk pregnancies, which carry a higher psychological and financial burden compared to spontaneous pregnancies (Oddens et al., 1999). The proportion of women aged 35 years or more is higher in ART pregnancies, therefore, they a more likely to be carrying a child affected by Down syndrome (Geipel et al., 1999; Pinborg et al., 2004; Weisz and Rodeck, 2006, Gjerris et al., 2008). Studies have also shown that foetuses conceived after intracytoplasmic sperm injection (ICSI) are known to have an increased risk of chromosomal aberrations (Aboulghar et al., 2001; Bonduelle et al., 2002; Jozwiak et al., 2004; Gjerris et al., 2008). Pregnancies conceived after ART are also associated with a higher rate of multiple pregnancies (Weisz and Rodeck, 2006, Gjerris et al., 2008). Maternal and fetal complications, such as foetal growth restriction, preeclampsia, preterm birth, congenital abnormalities, and low birth weight occur more often in assisted reproduction pregnancies (Helmerhorst et al., 2004; Amor et al., 2009; Williams and Sutcliffe, 2009; Henningsen et al., 2011). Women who have conceived after assisted reproductive techniques usually prefer to avoid invasive diagnostic procedures, such as amniocentesis and villus biopsy, due to the risk of miscarriage. Rather, they choose noninvasive screening before making a decision about invasive testing (Meschede et al., 1998; Schover et al., 1998; Geipel et al., 1999; Geipel et al., 2004). Pregnancies conceived by assisted reproduction techniques have also been reported to be associated with changes in the biochemical parameters of screening for Down syndrome,

Down Syndrome Screening in Pregnancies Conceived after Assisted Reproductive Technologies