Objective To describe glycemia and insulin administration in lactating women with type 1 diabetes and compare their energy intake, lactation onset, and postpartum weight to lactating women without diabetes.

Design A prospective observational study conducted at 2, 3, 6, 14, 42, and 84 days postpartum. Insulin dosage and glucose levels after fasting and at 80 and 110 minutes after eating (by measuring capillary blood glucose concentrations and glycated hemoglobin [HbA_1c] values) are described for women with type 1 diabetes. Dietary intake, weight, and lactation onset for women with type 1 diabetes are compared with those without the disease.

Subjects/setting Fourteen lactating women with type 1 diabetes and 25 women without diabetes (control subjects) were recruited from private obstetrician offices and high-risk prenatal clinics at 3 major medical centers.

Statistical analyses A repeated-measures 2-factor analysis of variance was used to determine group, time, and interaction effects between women with type 1 diabetes and the control group at 2, 3, 7, 14, 42, and 84 days postpartum.

Results Seven women with type 1 diabetes breast-fed through 84 days postpartum, although they perceived later onset of milk and had fasting and postprandial hyperglycemia. Their HbA_1c levels increased by 20%, confirming relative hyperglycemia. After adjustment for prepregnancy weight, women with type 1 diabetes consumed 7kcal fewer per kilogram per day than control subjects. Average insulin dose was returned to prepregnancy levels of 45.3±3.6U/d (least square means±standard error of the mean) by 1 week.

Application Achieving desired metabolic control during the establishment of lactation is difficult. A better understanding of energy and insulin needs and their relationship to lactation in women with type 1 diabetes is needed. J Am Diet Assoc. 1998; 98: 642–648.