BREASTFEEDING IS KNOWN TO IMPROVE INFANT HEALTH AND REDUCE RISK OF MANY DISEASES LATER IN LIFE. EFFORTS TO SUPPORT AND ENCOURAGE BREASTFEEDING IN THE UNITED STATES HAVE RESULTED IN STEADILYINCREASING RATES OF BREASTFEEDING BETWEEN 2009 AND 2016, ACCORDING TO THE CDC. HOWEVER, MANY MOTHERS WHO PLAN TO BREASTFEED OR START BREASTFEEDING ARE UNABLE TO CONTINUE. WE CURRENTLY UNDERSTAND VERY LITTLE ABOUT WHICH BIOLOGICAL OR MEDICAL FACTORSMAY KEEP A MOTHER FROM BEING ABLE TO BREASTFEED. HOWEVER, CURRENT DATA SHOWS THAT MOTHERS WHO HAVE INSULIN RESISTANCE OR HIGH BLOOD LIPIDS (CHOLESTEROL AND TRIGLYCERIDES) MAY HAVE TROUBLE BREASTFEEDING. PRODUCING MILK REQUIRES LARGE AMOUNTS OF ENERGY, PROVIDED BYFATTY ACIDS. HOWEVER, SOME FATTY ACIDS ALSO PLAY AN IMPORTANT ROLE IN REGULATING METABOLISM, INCLUDING INSULIN. THEREFORE, THE TYPES AND AMOUNTS OF FATTY ACIDS THAT ARE STORED IN THE BODY AND CIRCULATING IN THE BLOOD PROBABLY HAVE A LARGE IMPACT ON A MOTHER'S ABILITY TO BREASTFEED.WE HAVE PREVIOUSLY RECRUITED MOTHERS SOON AFTER BIRTH WHO WERE TRYING TO BREASTFEED, BUTBELIEVED THEY HAD LOW MILK PRODUCTION. THESE MOTHERS PARTICIPATED INAN EXPERIMENTAL TRIAL OF A TREATMENT FOR LOW MILK PRODUCTION. IN THIS STUDY, WE WILL MEASURE WHICH TYPES OF FATTY ACIDS ARE PRESENT IN THE BLOOD AND MILK OF THESE MOTHERS. IN ADDITION, WE WILL BE STUDYING AGROUP OF MOTHERS WHO WERE EXCLUSIVELY BREASTFEEDING AND DID NOT HAVE ANY PROBLEMS WITH MILK PRODUCTION. THIS WILL HELP US TO UNDERSTAND WHICH FATTY ACIDS AND BLOOD LIPIDS ARE ASSOCIATED WITH POOR MILK PRODUCTION AND START TO NARROW THE FOCUS ON WHICH POTENTIAL TREATMENTS MAYHELP MOTHERS WITH INSUFFICIENT MILK PRODUCTION.