A Comparison between Maternal Serum Free β-Human Chorionic Gonadotrophin and Pregnancy-Associated Plasma Protein A Levels in First-Trimester Twin and Singleton Pregnancies

Abstract
Objectives: To determine the levels of first-trimester free β-human chorionic gonadotrophin (free βhCG), pregnancy-associated plasma protein A (PAPP-A) and nuchal translucency (NT) in twin pregnancies. Methods: The study included 93 patients with twin pregnancy and 4,977 with singletons who underwent first-trimester testing using free βhCG, PAPP-A and NT at 10–13 weeks of gestational age. Results: In twin pregnancies, the maternal serum free βhCG level was 2.18 higher and the PAPP-A level was 2.38 higher than in singleton pregnancies. These marker levels were significantly higher than the expected 2.0 multiples of the median (MoM). In contrast, NT values did not differ between twins and singletons. Conclusion: These data may be used to establish first-trimester combined screening for twin pregnancies.