Objective: Providing effective dietary counselling so that pregnancy weight gain remains within the 2009 Institute of Medicine (IOM) guidelines requires accurate maternal energy intake measures. Current practice is based on self-reported intake that has been demonstrated unreliable. This study applies an objective calculation of energy intake from a validated mathematical model to identify characteristics of individuals more likely to misreport during pregnancy.
Methods: A validated maternal energy balance equation was used to calculate energy intake from gestational weight gain in 1,368 subjects. The difference between self-reported and model-predicted energy intake was tested for demographics, economic status, education level and maternal health status.
Results: A weight gain of 15.2 kg resulted in model-predicted intake during pregnancy of 2,882.97 ± 135.71 kcal day-1, which differed from self-reported intake of 2,180.5 ± 856.0 kcal day-1. The achieved weight gain exceeded the IOM guidelines; however, the model predicted weight gain from self-reported energy intake was below IOM guidelines. Higher income (p = 0.004), education (p = 0.003), birth weight (p = 0.017), gestational diabetes (p = 0.008) and pre-existing diabetes (p < 0.001) were associated with under-reported energy intake. More children living at home (p = 0.001) were associated with more accurate self-reported intake.
Conclusions: When assessing self-reported energy intake in pregnancy studies, birth weight, gestational diabetes status, pre-existing diabetes, higher income and education predict higher under-reporting. Clinicians providing dietary treatment recommendations during pregnancy should be aware that individuals with pre-existing diabetes and gestational diabetes mellitus are more likely to misreport their intake. Additionally, the systems model approach can be applied early in intervention to objectively monitor dietary compliance to treatment recommendations.
Keywords: Differential equation; maternal energy intake; mathematical model; pregnancy weight gain.