2025 Theses Doctoral

Incorporating Maternal Health into Pregnancy and Postpartum Public Health Policies: Paid Family Leave and Maternal Breast and Endometrial Cancer

Argov, Erica

Breastfeeding is an important health behavior associated with reduced cancer rates in the breastfeeding parent. Breastfeeding initiation and duration are modifiable for most women, and highly influenced by social and external factors. Research on maternal health benefits often use cumulative lifetime breastfeeding duration, while real-world breastfeeding interventions, education, support strategies (such as paid family leave (PFL)), and behaviors are, in practice, operationalized at the time of each birth, making data on per-birth measures more relevant, particularly as fertility rates (and therefore the lifetime number of births) decline. This dissertation aims to incorporate maternal health into pregnancy and postpartum policies by examining the association of per-birth breastfeeding durations with maternal cancer, and assessing the potential for PFL as a structural intervention to reduce breast and endometrial cancer risk.

The first chapter will provide background information, including the mechanisms for breastfeeding’s preventive effect on maternal cancer, the state of paid family leave in the US, describe what is known about the efficacy of PFL on increasing leave-uptake and breastfeeding durations, and describe the goals of the dissertation.

The next chapter will describe the results of a systematic literature review that identified 66 articles summarizing the association between per-birth breastfeeding duration and maternal cancer risk. This review found that the evidence on per-birth durations and non-breast cancers are lacking, as well as evidence looking at extended breastfeeding durations (>12 m) in the US, but concludes that a consistent association with per-birth breastfeeding duration exists for maternal breast cancer that does not appear to plateau; greater breastfeeding durations continue to decrease breast cancer risk beyond the initial postpartum period.

The third chapter will describe a state-level ecological study using US cancer registry data to evaluate the association of paid leave implementation in California with later breast and endometrial cancer rates by race/ethnicity, and, for breast cancer, by hormone receptor status and age. Results supported reduced breast and endometrial cancer incidence beginning to emerge beginning 10 years after PFL implementation, though most estimates were not statistically significant.

The fourth chapter describes a county-level ecological study using US cancer registry data and a county-level socioeconomic (SES) index to determine if there is variation in the association of California’s PFL implementation with cancer incidence by county-level SES. Results suggested that PFL was associated with reduced breast cancer incidence in CA for counties in low, but not high SES quartiles.

The final chapter discusses the overall conclusions and implications. Overall, this dissertation emphasizes the value of per-birth breastfeeding durations for maternal cancer risk, and identifies gaps in the related research, as well as provides an ecological-level foundation for future individual-level research that supports the potential for PFL in breast cancer prevention, particularly among low-SES areas.