Background: Maternal stress during utero has been shown to have negative health consequences on the offspring, including low birth weight and increased risk of adult disease. Variation in breastmilk may act as an environmental cue of maternal stress and continue to program the infant during early life. This research aimed to explore the role of breastmilk on developmental programming of the infant. Specifically, to examine how breastmilk may act as a medium for the exposure of stress between the mother and the offspring, and see if variation in insulin like growth factor-1 (IGF-1) a potential mechanism for the relationship. Methods: Survey-interviews, anthropometrics of the mother and offspring (height and weight), and breastmilk samples were collected for 31 breastfeeding mother-offspring pairs in the Tampa Bay area. Breastmilk was analyzed for IGF-1 and fat content. Maternal stress was measured through the PSS-10 and two self-reported ten-point stress scales. Offspring length for age and weight for age Z-scores were calculated using LMS equation. Results: PPS-10 score was negatively correlated with child length for age and weight for age Z-scores. Child length for age and weight for age Z-scores were also negatively correlated with the breastmilk fat variables (creamatocrit percent, fat g/dL, and kcal/dL). No relationships were found between breastmilk IGF-1 and offspring length for age, weight for age, or maternal stress. Conclusions: Results indicate that maternal stress may negatively impact offspring growth. However, more research is necessary to better understand if or how breastmilk fat may act as a mechanism to mediate offspring growth due to maternal stress. This sample had low levels and prevalence of detectable IGF-1, which likely contributed to the lack of statistical relationships. Further research using lower dilutions and larger samples sizes is necessary to better explore the potential role of breastmilk IGF-1 on offspring growth and/or its relationship to maternal stress.