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Endometriosis is a chronic gynecologic disease affecting approximately ten percent of women in the United States. Endometriosis lesions depend on estrogen for growth and maintenance and it is hypothesized that women with endometriosis have an altered hormonal and inflammatory state. Emerging evidence suggests that women with endometriosis may be at increased risk of breast cancer. Using data from the Nurses’ Health Study II, a prospective cohort of 116,430 women, this thesis investigates endometriosis and breast health. Specifically we investigated whether endometriosis influences risk of breast cancer and benign breast disease and alters mammographic density. Lastly, we investigated whether breastfeeding duration influenced endometriosis risk. Across all analyses, endometriosis was confirmed using laparoscopy, considered the clinical diagnostic gold standard. Information on breast cancer and benign breast disease was collected every two years and confirmed by medical record or pathology slides respectively. Mammographic density was measured from mammograms of a subset of participants without breast cancer using a computer assisted thresholding technique. Detailed breastfeeding information was collected between 1997-2001. Cox proportional hazard models were used to calculate Hazard Ratios (HR) and 95% confidence intervals (CI) and linear regression using generalized estimating equations was used to estimate difference in mammographic density measurements. We found that while women with endometriosis were not at increased risk of overall breast cancer (HR:1.05, CI:0.95-1.16), they did appear to be at an increased risk of ER+/PR- tumors (HR:1.72, CI:1.27-2.32). Endometriosis moderately increased risk of biopsy confirmed benign breast disease, both proliferative (HR:1.23, CI:1.01-1.51) and non-proliferative lesions (HR:1.25, CI:0.93-1.69). Endometriosis did not significantly alter mammographic density. History of breastfeeding was inversely associated with endometriosis (P-value, test for linear trend: <0.0001), which was partially, but not fully mediated through postpartum amenorrhea. Our findings report novel associations with endometriosis and ER+/PR- breast tumors and benign breast disease lesions and no difference in mammographic density. This may elucidate avenues of research on how endometriosis lesions may alter chronic disease risk. Given the debilitating symptoms and few known modifiable risk factors of endometriosis, our findings of an inverse relationship with breastfeeding and endometriosis may inform treatments and prevention strategies for endometriosis in the future.

In 2013, approximately 289,000 women died from pregnancy-related causes and 2.8 million newborns died within the first 28 days of life. The vast majority of these deaths occur in resource-limited settings. This work examines risk and protective factors for the development of several perinatal complications that put mothers and their infants at risk for adverse health outcomes. We explored determinants of preeclampsia and gestational hypertension among women in Dar es Salaam, Tanzania. We also examined the effects of pregnancy spacing intervals on perinatal outcomes in that group of women. We used log binomial regression to obtain risk ratios and 95% confidence intervals for the development of the adverse pregnancy outcomes of interest. We also looked at the efficacy of an intervention aimed at improving neonatal outcomes by conducting a systematic review and meta-analysis of the effects of kangaroo mother care on neonatal morbidity and mortality. We found that nulliparity, history of hypertension, urinary tract infection, low calcium intake, history of preeclampsia, and history of preterm birth were associated with an increased risk of developing preeclampsia among women in Dar es Salaam. Risk factors for gestational hypertension included a history of diabetes, elevated blood pressure at study enrollment, increased mid-upper arm circumference, high hematocrit, low mean corpuscular volume, a history of miscarriage or stillbirth, and older age at first pregnancy. Twin gestation and increased body mass index were risk factors for both types of hypertensive disorders of pregnancy among women in Tanzania. After a live birth, inter-pregnancy intervals less than six months were associated with an increased the risk of having a low birth weight baby in the next pregnancy; while after a stillbirth, short inter-pregnancy intervals were associated with increased risk of stillbirth and perinatal death. Providing kangaroo mother care to infants after birth was associated with decreased neonatal morbidity and mortality and increased likelihood of exclusive breastfeeding when compared to conventional care. These findings can help identify women and infants at increased risk for developing pregnancy-related complications and contribute to informing development of evidence-based maternal, newborn, and family planning programs and policies., Epidemiology