title: Association between low day 16 hCG and miscarriage after proven cardiac activity.
abstract: OBJECTIVE
  To investigate an association between low human chorionic gonadotrophin (hCG) levels at the end of the first week of implantation and later clinical miscarriage occurring after ultrasound confirmation of a live pregnancy.
  
  
  METHODS
  This was an observational retrospective study of 1,054 women who underwent in vitro fertilization and achieved an ultrasound-confirmed live singleton pregnancy with cardiac activity. The incidence of miscarriage diagnosed at 8-19 weeks +6 days of gestation was estimated in these 3 subgroups according to their hCG concentrations at day 16 after conception: less than the 25th, 25th-75th, and more than the 75th percentiles.
  
  
  RESULTS
  The overall incidence of miscarriage was 11.1% (117/1,054), and the median gestational age at diagnosis was 10 weeks and 4 days. The median (95% confidence interval) day 16 hCG level in the miscarriage group was 182 mIU/mL (157-211), significantly lower than the median level in those who had an ongoing pregnancy (223 mIU/mL [213-233], P < .003). There was an increasing risk of miscarriage associated with decreased hCG levels (8.0% at > 75th percentile; 9.9% at 25th-75th percentiles; 16.7% at < 25th percentile; P = .003).
  
  
  CONCLUSIONS
  Low hCG levels in very early pregnancy are associated with an increased risk of miscarriage occurring after the clinical recognition of pregnancy. The mechanisms underlying late first-trimester and second-trimester miscarriages may have begun as early as the first week of implantation.
  
  
  METHODS
  III.
authors.affiliation: Department of Obstetrics and Gynaecology, Monash University, Monash Medical Centre, Clayton, Victoria, Australia. stong@unimelb.edu.au
authors.forename: Stephen
authors.initials: S
authors.lastname: Tong
authors.forename: Euan M
authors.initials: EM
authors.lastname: Wallace
authors.forename: Luk
authors.initials: L
authors.lastname: Rombauts
mesh_terms: D000022:Abortion, Spontaneous / Q000097:blood* / Q000453:epidemiology*; D000328:Adult; D006063:Chorionic Gonadotropin / Q000097:blood*; D005260:Female; D006340:Heart Rate, Fetal; D006801:Humans; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D012189:Retrospective Studies
chemical_list: D006063:Chorionic Gonadotropin