title: The concurrent validity between leptin, BMI and skin folds during pregnancy and the year after.
abstract: BACKGROUND
  From a public health perspective it is important to know which of the currently used methods to estimate changes in maternal body fat during pregnancy and the year thereafter is the most adequate.
  
  
  OBJECTIVE
  To evaluate the concurrent validity between leptin and surrogates of fat measures: body mass index (BMI) and the sum of four skin folds.
  
  
  METHODS
  Data from the New Life(style) intervention study were analysed as a cohort study.
  
  
  METHODS
  Midwife practices in The Netherlands.
  
  
  METHODS
  Healthy pregnant nulliparous women.
  
  
  METHODS
  Anthropometric measurements were done and blood was collected at 15, 25 and 35 weeks of pregnancy and at 6, 26 and 52 weeks after delivery. Data were used if at least 4 out of the 6 measurements were available, leaving 87 women in the analyses. Spearman's correlation coefficients between leptin and BMI and between leptin and the sum of skin folds were calculated for each time point and for the changes between the time points.
  
  
  RESULTS
  Correlations between leptin and BMI varied from 0.69 to 0.81. Correlations between leptin and the sum of skin folds were comparable, varying between 0.65 and 0.81.Correlations between changes in leptin and changes in BMI and the sum of skin folds, respectively, were much lower compared with cross-sectional correlations.
  
  
  CONCLUSIONS
  Because of the high correlation among the three methods and because of the overlapping intervals, all methods seem to be equally adequate to estimate changes in maternal body fat during pregnancy and the year thereafter.
authors.affiliation: 1] Department of Public and Occupational Health, EMGO Institute for Health and Care Research, VU University Medical Center, Amsterdam, The Netherlands [2] Department of Gynaecology, Medisch Centrum Jan van Goyen, Amsterdam, The Netherlands.
authors.forename: C L
authors.initials: CL
authors.lastname: van der Wijden
authors.forename: H A
authors.initials: HA
authors.lastname: Delemarre-van der Waal
authors.forename: W
authors.initials: W
authors.lastname: van Mechelen
authors.forename: M N M
authors.initials: MN
authors.lastname: van Poppel
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