Prediction of excessive gestational weight gain from week-specific cutoff values: a cohort study

OBJECTIVE: To assess the prognostic validity of the Institute of Medicine/National Research Council (IOM/NRC) week-specific cutoff values for inadequate or excessive total gestational weight gain (GWG) by 4-week intervals. STUDY DESIGN: We merged data from two German cohorts (LMU cohort (all maternal-weight categories) and PEACHES cohort (obese women)) to provide information on GWG for 749 women (365 normal weight, 199 overweight and 185 obese). We calculated the prognostic values for suboptimal and excessive GWG according to the IOM/NRC cutoff values. RESULT: The positive predictive values for excessive total GWG for those who experienced excessive GWG early in pregnancy was 70.1% (95% confidence interval (CI) 60.5; 78.6) as of week 12/1 to 16/0 in normal-weight women, 89.5% (95% CI 75.2; 97.1) and 95.2 (76.2; 99.9) 95.2% (95% CI 76.2; 99.9) as of week 8/1 to 12/0 for overweight and obese women, respectively. In absence of excessive GWG as of week 12/1 to 16/0, normal-weight women had 77.5% (95% CI 77.1; 83.1) probability of not experiencing excessive total GWG (negative predictive value). In overweight and obese women, the negative predictive value was considerably lower up to week 24/1 to 28/0 (60.0% (95% CI 48.8; 70.5) in week 20/1 to 24/0 and 50.6% (95% CI 39.3; 61.9) in week 24/1 to 28/0). Most women with inadequate GWG in the first and second trimester had adequate total final GWG (positive predictive value for total inadequate GWG o50% up to week 16/1 to 20/0 in all groups). CONCLUSION: As women with excessive weight gain can be identified with high confidence if the GWG exceeds the IOM/NRC week-specific cutoff values, interventions may be initiated early in pregnancy.