title: Can early β-human chorionic gonadotropin predict birth of singletons and twins after in vitro fertilization?
abstract: OBJECTIVE
  To assess the predictive value for clinical pregnancy outcome of β-hCG level at 13 d after embryo transfer.
  
  
  METHODS
  Retrospective study of IVF clinical pregnancies diagnosed at 6 weeks. We calculated the value of β-hCG level at 13 d after embryo transfer to predict live births.
  
  
  RESULTS
  We analyzed 177 IVF cycles between 2009 and 2014 (50 singleton births, 50 twin births, 27 sets with a vanishing twin, 43 first trimester singleton pregnancy loss and seven first trimester total twin pregnancy loss). Singleton pregnancies with a β-hCG concentration <85 mIU/mL had an 89% risk of having a first trimester loss whereas a concentration >386 mU/mL had a 91% chance of a live birth. Twin pregnancies with a concentration <207 mIU/mL had only a 33% chance of delivering twins and a 55% risk of having a vanishing twin; whereas a level >768 mIU/mL was associated with a 81% chance of live twin birth and a low risk (19%) of having a vanishing twin. Age, type and duration of infertility, body mass index (BMI) and number of fertilized oocytes did not affect these calculations.
  
  
  CONCLUSIONS
  β-hCG level at 13 d after embryo transfer might predict outcomes in clinical singleton and twin pregnancies following IVF.
authors.affiliation: a Department of Obstetrics and Gynecology, Unit of Reproductive Medicine , Hospitalar Center São João , Porto , Portugal.
authors.forename: Ana
authors.initials: A
authors.lastname: Póvoa
authors.affiliation: b Department of Clinical Epidemiology, Predictive Medicine and Public Health, Faculty of Medicine, University of Porto , Porto , Portugal.|c EPI Unit, Institute of Public Health, University of Porto , Porto , Portugal.
authors.forename: Milton
authors.identifier: http://orcid.org/0000-0002-5787-4871
authors.initials: M
authors.lastname: Severo
authors.affiliation: a Department of Obstetrics and Gynecology, Unit of Reproductive Medicine , Hospitalar Center São João , Porto , Portugal.
authors.forename: Pedro
authors.initials: P
authors.lastname: Xavier
authors.affiliation: d Department of Gynecology and Obstetrics, Faculty of Medicine , University of Porto/Hospitalar Center S. João, Porto , Portugal.|e Instituto de Investigação e Inovação em Saúde, Universidade do Porto , Porto , Portugal.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Matias
authors.affiliation: f Department of obstetrics and Gynecology , Kaplan Medical Center, Rehovot, and the Hadassah-Hebrew University School of Medicine , Jerusalem , Israel.
authors.forename: Isaac
authors.initials: I
authors.lastname: Blickstein
mesh_terms: D000022:Abortion, Spontaneous / Q000097:blood* / Q000453:epidemiology; D000328:Adult; D015415:Biomarkers / Q000097:blood; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000097:blood*; D004624:Embryo Transfer; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D050498:Live Birth; D011247:Pregnancy; D011256:Pregnancy Outcome; D011261:Pregnancy Trimester, First / Q000097:blood*; D059285:Pregnancy, Twin / Q000097:blood* / Q000706:statistics & numerical data; D012189:Retrospective Studies
chemical_list: D015415:Biomarkers; D018997:Chorionic Gonadotropin, beta Subunit, Human
keywords: assisted reproduction; pregnancy outcome; twins; vanishing twins; β-hCG