Biological factors may cause overweight and obese mothers to quit breastfeeding their infants.

Cornell University and Basset Hospital researchers in New York found that these women have lower prolactin responses to suckling. Prolactin hormone stimulates mammary glands to produce milk after birth, and decreased responses can lead to a much shorter period of breast-feeding.

Researchers measured prolactin in 40 mothers and found that overweight and obese women produced far less 48 hours after birth and moderately less a week later, compared with women of normal weight.

Currently, 29% of new mothers continue breast-feeding for six months.