Association of a high-protein and low-glycemic-index diet during pregnancy with offspring growth and obesity until the age of 18 years - a target trial emulation.

Background: Maternal pre-pregnancy BMI and excessive gestational weight gain (GWG) are associated with offspring obesity. Moreover, maternal dietary patterns, particularly protein intake and glycemic index, influence GWG and fetal development. This study aimed to investigate the association of a high-protein, low-glycemic-index (HPLGI) diet during pregnancy with offspring growth and obesity.

Methods: Using observational data from the Danish National Birth Cohort, a target trial emulation was conducted to investigate the association of an HPLGI diet during pregnancy on offspring growth up to 18 years of age. A cohort of 17,551 women who met the inclusion criteria was categorized into exposure groups based on their protein intake and glycemic index to emulate the groups in the APPROACH trial.

Results: Maternal characteristics varied between the exposure groups, with the HPLGI women exhibiting 1.67 kg higher pre-pregnancy weight and 0.49 kg/m² BMI, with no differences in GWG. Offspring outcomes were assessed at various ages, and a linear mixed model was used, including potential confounders. Offspring born to women following an HPLGI diet during pregnancy had 2.59 kg higher body weight and 0.72 kg/m² higher BMI at 18 years compared to those from the moderate-protein, moderate-glycemic-index (MPMGI) group.

Conclusion: An HPLGI diet during pregnancy was associated with higher offspring body weight and BMI at 18 years of age compared to an MPMGI diet. These findings suggest that maternal dietary composition during pregnancy may have long-term implications for offspring growth and obesity risk, underscoring the importance of evaluating dietary recommendations during pregnancy.