title: Individual deviations in human chorionic gonadotropin concentrations during pregnancy.
abstract: BACKGROUND
  Serum and urine human chorionic gonadotropin (hCG) vary greatly during the course of pregnancy. We investigated the cause of this variation.
  
  
  METHODS
  Eighty-two women provided daily urine samples during the first 6 weeks of gestation. First-void urine samples were monitored for luteinizing hormone (LH) and hCG.
  
  
  RESULTS
  Variation was wide when pregnancy hCG anchoring to the last menstrual period (variation 677 ± 786-fold) or to LH peak (variation 810 ± 936-fold). When pregnancy was anchored to the day of implantation (variation 187 ± 123-fold) variation was significantly reduced (P < .00005). Individual differences in the rate of hCG production were examined. hCG production ranged from 1.52-fold to 2.92-fold per day. Rate differences in hCG were also a major source of hCG variation.
  
  
  CONCLUSIONS
  Two factors are responsible for the wide fluctuation in hCG concentrations, first dating pregnancies to the start of the last menstrual period rather than the timing of implantation and second, individual pregnancy differences in the rate of hCG production.
authors.affiliation: USA hCG Reference Service, Department of Obstetrics and Gynecology, University of New Mexico School of Medicine, Albuquerque, NM 87131, USA. larry@hcglab.com
authors.forename: Laurence A
authors.initials: LA
authors.lastname: Cole
mesh_terms: D006063:Chorionic Gonadotropin / Q000652:urine*; D005260:Female; D005865:Gestational Age; D006801:Humans; D007986:Luteinizing Hormone / Q000652:urine; D008597:Menstrual Cycle; D011247:Pregnancy / Q000652:urine*
chemical_list: D006063:Chorionic Gonadotropin; D007986:Luteinizing Hormone