Women with type 1 diabetes gain more weight during pregnancy compared to age-matched healthy women despite a healthier diet: a prospective case–control observational study

PURPOSE: Women with type 1 diabetes mellitus (T1D), especially those with suboptimal glucose control, have 3–4 greater chances of having babies with birth defects compared to healthy women. We aimed to evaluate glucose control and insulin regimen modifications during the pregnancy of women with T1D, comparing the offspring’s weight and the mother’s weight change and diet with those of non-diabetic, normal-weight pregnant women. METHODS: Women with T1D and age-matched healthy women controls (CTR) were consecutively enrolled among pregnant women with normal weight visiting our center. All patients underwent physical examination and diabetes and nutritional counseling, and completed lifestyle and food intake questionnaires. RESULTS: A total of 44 women with T1D and 34 healthy controls were enrolled. Women with T1D increased their insulin regimen during pregnancy, going from baseline 0.9 ± 0.3 IU/kg to 1.1 ± 0.4 IU/kg (p = 0.009), with a concomitant significant reduction in HbA1c (p = 0.009). Over 50% of T1D women were on a diet compared to < 20% of healthy women (p < 0.001). Women with T1D reported higher consumption of complex carbohydrates, milk, dairy foods, eggs, fruits, and vegetables, while 20% of healthy women never or rarely consumed them. Despite a better diet, women with T1D gained more weight (p = 0.044) and gave birth to babies with higher mean birth weight (p = 0.043), likely due to the daily increase in insulin regimen. CONCLUSION: A balance between achieving metabolic control and avoiding weight gain is crucial in the management of pregnant women with T1D, who should be encouraged to further improve lifestyle and eating habits with the aim of limiting upward insulin titration adjustments to a minimum.