Prenatal diagnosis after ART success: the role of early combined screening tests in counselling pregnant patients

First-trimester Down syndrome screening may cause a higher false positive rate in pregnant patients who have undergone ART (assisted reproductive technologies). The aim of this paper is to contribute to this analysis with the second largest series of combined biophysical and biochemical tests in the first trimester of pregnancy after ART. One hundred and forty-two singleton successful ART pregnancies were selected for this study: 50 pregnancies induced by using in-vitro fertilization (IVF), and 92 using intracytoplasmic sperm injection (ICSI). Each patient was matched with three naturally conceived pregnancies based on maternal age and gestational age. Free beta-HCG and PAPP-A were measured on dried blood spots and converted to MoMs. Nuchal translucency (NT) was measured by certified operators. Mean maternal age was 33 +/- 4. NT, free beta-HCG and PAPP-A values of the control cases were not significantly different from local standards evaluated on 3043 cases. NT between ART pregnancies and matched controls was not significantly different. PAPP-A was reduced but not significantly lower in ART pregnancies. Free beta-HCG was the only analyte that resulted in significantly higher values in ART pregnancies (1.12 MoM) versus controls (0.99 MoM). No significant differences were found for biochemical values observed between ICSI and IVF patients. The screen positive rates observed in ART and control pregnancies were 5.5 per cent and 4.6 per cent respectively. NT measurements were not affected by ART pregnancies. Our results (non-significant lower values of PAPP-A and significantly higher free beta-HCG values) were consistent with other reported series. The increase in the screen positive rate determined by these biological variations was not greater than 0.9 per cent. This higher false positive rate has a negligible impact on counselling ART patients. The algorithm used to calculate the relative risk after the combined tests should not be changed until the detection rate of trisomies in ART pregnancies is not fully disclosed by larger series.