Childhood obesity is a critical global public health concern. Breastfeeding is the ideal choice for infant nutrition. However, rapid and excess weight gain during infancy predicts later, even among breastfed infants. This risk is higher if mothers are obese and/or diabetic. Composition of bioactive components of breast milk may differ based between mothers who are normal weight (NW), overweight, or who have diabetes. Obesity and Type 2 Diabetes are associated with overall increases in inflammation and oxidative stress, but how breast milk composition is affected remains unknown. The investigators overarching goal is to determine how maternal obesity and Type 2 Diabetes impacts human breast milk composition and how differences in composition may impact infant growth and fat development. The investigators are undertaking a study that follows 20 Normal Weight, 20 Obese, 20 Gestational Diabetic, and 20 Type 2 Diabetic mothers and their infants over the first 4 months of life. The investigators will track infant weight and fat gain and monitor maternal glucose control. The investigators will also collect breast milk samples over the first 4 months and measure concentrations of growth and appetite hormones, cytokines, markers of oxidative stress and nutrient composition in milk. The investigators predict that concentrations of growth-regulatory hormones (insulin and leptin) in addition to the inflammatory cytokines and markers of oxidative stress will be lowest in breast milk from NW mothers, higher in breast milk from obese and gestational diabetic mothers, and highest in Type 2 Diabetic mothers' breast milk. The investigators expect these differences will be most pronounced in the first 2 weeks after birth. The investigators also predict that breast milk concentrations of these biomarkers will be associated with infant fat gain. What the investigators find will help understand how early infant nutrition and growth may affect that child's later risk of obesity.

Inclusion Criteria:

• Between 28-40 weeks gestation
• Plan to Exclusively Breastfeed for at least 5 months
• Between 20 - 35 years old
• Carrying a singleton pregnancy
• Parity less than or equal to 5
• Pre-pregnancy BMI between 18.5 and 39.9

Exclusion Criteria:

• No known infant anomalies or birth defects
• Maternal Type 1 Diabetes
• Maternal major medical condition (ie: Kidney Disease or Pre-eclampsia)
• Delivery of the infant before 35 weeks gestation
• Smoking During pregnancy

We will recruit pregnant women in the Denver Colorado area who plan to deliver their infant at the University of Colorado Hospital, and plan to exclusively breastfeed their infant for at least 5 months.