BACKGROUND: The aim of this study was to compare the maternal mid-trimester free β-HCG and alphafetoprotein (AFP) levels in pregnancies conceived by assisted reproduction technology and spontaneous pregnancies in Down's syndrome screening. The influence of the number of embryos transferred and the amount of gonadotrophins used on the marker levels was also evaluated. METHODS: The study population consisted of 58 IVF, 32 ICSI and 26 frozen embryo transfer (FET) singleton pregnancies. The levels

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... f β-HCG and AFP were compared with the control group of 6548 singleton spontaneous pregnancies. RESULTS: The false positive rate (FPR) in the Down's syndrome screening was 19% overall in assisted reproductive technology pregnancies, being highest (30.8%) in the FET group. The free β-HCG multiples of the median (MoM) values were statistically significantly elevated only in the FET group (1.33 MoM; P ⍧ 0.012). A positive correlation between the number of embryos transferred and the marker levels was observed in the IVF group. No correlation was found between the amount of gonadotrophin medication used and the marker levels. CONCLUSIONS: The present data confirm that the overall FPR in the serum screening for Down's syndrome in assisted reproduction pregnancies is high, resulting in unnecessary invasive procedures.