The goal of this observational study is to investigate the concentrations of leptin, insulin, liver expressed antimicrobial peptide 2 (LEAP2), and cortisol in plasma and breast milk and their relationship with eating behavior, growth, adiposity and with the levels of these hormones in infants, comparing mothers with normal weight and with pre-pregnancy overweight/obesity. The main question\[s\] it aims to answer are:
* Are maternal hormones associated with child growth and adiposity * Are maternal hormone receptors associated with child growth and adiposity * Are infant hormones and their receptors associated with child growth and adiposity * Are maternal and infant hormones and their receptors associated with child eating behavior Participants will provide milk and blood samples. Researchers will compare mothers with normal weight and with pre-pregnancy overweight/obesity to see if there are differences in child growth and adiposity .
Lactating women with pre-pregnancy normal weight and overweight or obesity as described by the World Health Organization.
Diabetes (Type I or II or gestational)
Multiple pregnancy
Hypertensive disorders during pregnancy
Delivery of pre-term infant (<37 weeks).