Comparison of First Trimester Screening for Down's Syndrome Using Free Beta-Human Chorionic Gonadotropin and Pregnancy-Associated Plasma Protein-A Levels between Spontaneous and IVF Pregnancies at 12 Weeks of Gestation.

Background: In some previous studies, it was shown that first trimester screening tests produce equivocal results in fertilization (IVF) pregnancies. The purpose of this study was to compare free beta-human chorionic gonadotropin (β-hCG) and pregnancy-associated plasma protein-A (PAPPA) levels between single normal and IVF pregnancies during 11 to 13 week (+ 6 day) of gestational age.

Materials And Methods: In this observational cohort study, 300 consecutive single IVF pregnancies and 700 single normal pregnancies were enrolled at about 11-13 week + 6 day gestational age and levels of free β-hCG and PAPPA were compared between the groups.

Results: The results demonstrated that PAPPA (P=0.026) was significantly lower and β-hCG (P=0.030) was significantly higher in IVF pregnancies. The other factors including nuchal translucency (NT) and crown-rump length (CRL) and demographic characteristics did not significantly differ between the groups (P>0.05).

Conclusion: This study showed that PAPPA levels are lower but free β-hCG levels are higher in single IVF versus normal pregnancies. This finding could be related to different placentation in intracytoplasmic sperm injection (ICSI) technique because of alterations in oocyte cytoplasm. Therefore, these markers may need to be adjusted in assisted reproductive technology (ART) conceptions. Further research should be done to obtain optimal cut-off for these markers in first trimester screening for detection of Down syndrome in ART pregnancies.