Prognostic effect of subsequent childbirth after the diagnosis of breast cancer using propensity score matching analysis

Background Among younger patients, one of the important concerns is whether they can give birth safely. Although previous studies have investigated this topic, many aspects remain unclear owing to potential biases. We aimed to evaluate the prognostic effect of subsequent childbirth after the diagnosis using propensity score matching. Methods A single-center retrospective cohort study was conducted. This study included patients aged ≤ 45 years, diagnosed with breast cancer between 2005 and 2014. Patients with and without subsequent childbirth were assigned to the childbirth and non-childbirth cohorts, respectively. Relapse-free survival (RFS) and overall survival (OS) of the childbirth cohort were compared with those of the non-childbirth cohort. The covariates in the propensity score model included age, tumor size, node status, number of preceding childbirths before the diagnosis, estrogen receptor, and human epidermal growth factor receptor 2 status. Results 104 patients with childbirth and 2250 without childbirth were assigned to the respective cohorts. At a median follow-up of 82 months, the childbirth cohort showed a significantly longer RFS than the non-childbirth cohort (HR = 0.469 [0.221–0.992]; p = 0.047). There was no significant difference in the OS (HR = 0.208 [0.029–1.494]; p = 0.119). After matching, subsequent childbirth was not significantly associated with RFS (HR = 0.436 [0.163–1.164], p = 0.098) and OS (HR = 0.372 [0.033–4.134], p = 0.402). Conclusions Subsequent childbirth was not associated with an increased risk of relapse and mortality. It is important to make younger patients aware of these novel findings and aid them in their decision-making.