title: A comparison between maternal serum free beta-human chorionic gonadotrophin and pregnancy-associated plasma protein A levels in first-trimester twin and singleton pregnancies.
abstract: OBJECTIVE
  To determine the levels of first-trimester free beta-human chorionic gonadotrophin (free betahCG), 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 betahCG, PAPP-A and NT at 10-13 weeks of gestational age.
  
  
  RESULTS
  In twin pregnancies, the maternal serum free betahCG 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.
  
  
  CONCLUSIONS
  These data may be used to establish first-trimester combined screening for twin pregnancies.
authors.affiliation: Prenatal Diagnosis Unit, Genetic Institute, Sourasky Medical Center, Sourasky, Tel Aviv, Israel.
authors.forename: Roy
authors.initials: R
authors.lastname: Mashiach
authors.forename: Avi
authors.initials: A
authors.lastname: Orr-Urtreger
authors.forename: Yuval
authors.initials: Y
authors.lastname: Yaron
mesh_terms: D000328:Adult; D016009:Chi-Square Distribution; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000097:blood*; D005260:Female; D006801:Humans; D016011:Normal Distribution; D011247:Pregnancy; D011261:Pregnancy Trimester, First / Q000097:blood*; D011272:Pregnancy, Multiple / Q000097:blood* / Q000706:statistics & numerical data; D011266:Pregnancy-Associated Plasma Protein-A / Q000378:metabolism*; D014427:Twins / Q000706:statistics & numerical data
chemical_list: D018997:Chorionic Gonadotropin, beta Subunit, Human; D011266:Pregnancy-Associated Plasma Protein-A