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To compare levels of β-hCG and estradiol collected during the first trimester in singleton and twin pregnancies following assisted reproduction technologies (ART).We prospectively evaluated 50 singleton and 47 dichorionic twin pregnancies that eventually ended in live births. Patients were recruited from a single ART center with standard treatment protocols followed by fresh embryo transfers. Hormone measurements were performed within a narrow gestational age range and analyzed in a single laboratory thus minimizing inter- and intra-assay variability. We measured serum β-hCG at 13 days after embryo transfer as well as samples of β-hCG and estradiol at 8-9 weeks+6 days.No significant differences existed between singletons and twins in respect to demographic and cycle characteristics. β-hCG and estradiol were all significantly higher in twins (P<0.05).The data confirms the higher levels of β-hCG and estradiol in twins, pointing to the potential role of these placental hormones in early support of a twin pregnancy.