title: Only two-phase models, computed independently for males and females, are appropriate to describe fetal head growth.
abstract: OBJECTIVE
  To establish an accurate mathematical model describing fetal head growth, taking into account gender differences and changes in growth rate during gestation.
  
  
  METHODS
  Ultrasound measurements of head circumference and biparietal diameter were made on 1,336 normal fetuses (684 males and 652 females) in the Maternité Régionale de Nancy (France). A new two-phase model, taking into account an alteration in growth kinetics at 30 gestational weeks, was computed independently for male and female data. The accuracy of this model was tested and compared with three current mathematical models: a linear-quadratic, a linear-cubic, and the Rossavik and Deter (1984) models.
  
  
  RESULTS
  In all models, including ours, the coefficients of determination (R(2)) were high (> or =0.999), so long as male and female data were computed separately. However, the standard error estimates (SEE) of our two-phase model were much lower (0.13 < or = SEE < or = 0.57) than the SEE of the three other models when computed over the whole gestational period (0.49 < or = SEE < or = 2.69); nevertheless, when these three other models were computed for these two successive periods, their SEE decreased, and data fitting was improved.
  
  
  CONCLUSIONS
  Only two-phase mathematical models, computed independently for male and female data, accurately describe the kinetics of fetal head growth. They should be used to calculate growth standards and to perform an exact diagnosis of impaired growth.
authors.affiliation: UPR 2147 du CNRS, Paris, France.
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Pineau
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Guihard-Costa
authors.forename: Pierre
authors.initials: P
authors.lastname: Droullé
mesh_terms: D002508:Cephalometry; D003430:Cross-Sectional Studies; D005314:Embryonic and Fetal Development; D005260:Female; D005317:Fetal Growth Retardation / Q000000981:diagnostic imaging; D005865:Gestational Age; D006257:Head / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D008433:Mathematics; D008954:Models, Biological; D012727:Sex Characteristics; D016216:Ultrasonography, Prenatal