Using Mixture Models with Linear Predictors to Identify Incorrect Gestational Age in State Birth Records
Paediatric and Perinatal Epidemiology, 07/05/2012

Leiss JK et al. – These results suggest that (1) including these two covariates as linear predictors of the means and mixing proportions gives the best model for identifying births with incorrect reported gestational age, (2) late entry into prenatal care is a mechanism by which erroneously short last–menstrual–period–based gestational ages are generated, and (3) including linear predictors of the mixing proportions in the model increases the validity of the classification of incorrect reported gestational age.

• The authors included covariates in the models as linear predictors of the means of the component distributions and the proportion of births in each component.
• This allowed both the means and the proportions to vary across levels of the covariates.

• The final model included maternal age and timing of entry into prenatal care.
• The proportion of births in the right-side distribution was lowest for older mothers who entered prenatal care early, higher for teen mothers who entered prenatal care early, higher still for older mothers who entered prenatal care late, and highest for teens who entered prenatal care late.
• Over 44% of births were classified as incorrect reported gestational age.