title: Weight adjustment of serum markers in early first-trimester prenatal screening for Down syndrome.
abstract: OBJECTIVE
  To assess whether existing weight correction formulas for PAPP-A and free-beta-hCG developed for weeks 11 to 14 can be applied to pregnancies in weeks 8 to 10.
  
  
  METHODS
  Development of formulas based on limited data sets of 8- to 10-week pregnancies and comparison with existing formulas. Calculation of median MoMs adjusted with different formulas for weight correction.
  
  
  RESULTS
  Weight correction formulas for the gestational age of 11 to 14 weeks were not appropriate in the 8- to 10-week gestational age interval for PAPP-A, whereas existing weight correction formulas could be applied to free-beta-hCG, independent of gestational age interval.
  
  
  CONCLUSIONS
  If PAPP-A is used in different gestational age intervals, weight corrections should be developed for the interval.
authors.affiliation: Department of Clinical Biochemistry, Statens Serum Institute, Denmark. TLI@SSI.dk
authors.forename: Tina
authors.initials: T
authors.lastname: Sørensen
authors.forename: Severin Olesen
authors.initials: SO
authors.lastname: Larsen
authors.forename: Michael
authors.initials: M
authors.lastname: Christiansen
mesh_terms: D001835:Body Weight; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000097:blood*; D004314:Down Syndrome / Q000175:diagnosis*; D005260:Female; D005865:Gestational Age; D006801:Humans; D016014:Linear Models; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011266:Pregnancy-Associated Plasma Protein-A / Q000032:analysis*; D011296:Prenatal Diagnosis / Q000379:methods*
chemical_list: D018997:Chorionic Gonadotropin, beta Subunit, Human; D011266:Pregnancy-Associated Plasma Protein-A