Factors associated with gestational breast cancer: case-control study.

The prevalence of gestational breast cancer (GBC) is 1:3,000-10,000 pregnancies. This study aims to identify the risk factors associated with GBC. This case-control study was conducted in the period between January 2004 and December 2014 at a reference maternity hospital for high-risk pregnancies in Rio de Janeiro. Two controls were selected for each case, totaling 21 GBC cases and 42 controls. Data were collected through a review of medical and hospitalization and delivery records. Reproductive, obstetrical, sociodemographic and health-related characteristics were investigated. Results: The mean age of pregnant women in both groups was 35.5 years. Menarche's mean age was also similar (12.3 years) in both groups. Mother's age at first pregnancy was > 30 years in 28.6% of the patients with GBC and in 2.4% of the control group (p = 0.03). Crude and adjusted odds ratio and their respective CI 95% were calculated through conditional logistic regression paired by mother's age. The results show that the risk for GBC increases 27% for each additional year of mother's age at first pregnancy (p < 0.02) and that mothers with lower schooling had higher risk of GBC (OR = 8.49). Conclusion: Our data confirm the association of primiparity over 30 years of age and low level of schooling with GBC.