Background: Pregnancy-associated breast cancer (PABC) is a rare disease with increasing incidence. The prognosis, pregnancy outcomes and subsequent ovarian function of PABC patients are attracting attention. Methods: Sixty-three PABC patients and 126 age-matched non-PABC patients were obtained in Tongji Hospital from January 2011 to September 2019. The clinical characteristics and ovarian function of PABC patients were compared with those of non-PABC patients. The pregnancy outcomes and neonatal outcomes of patients with breast cancer diagnosed during pregnancy (BCP) were described. Nonparametric tests, the chi(2)-test Kaplan-Meier, Cox regression and binomial logistic regression were used for analysis. Results: PABC patients were diagnosed with a more advanced tumour stage (II: 47.6% vs. 45.2%, III: 33.3% vs. 19.8%, IV 3.2% vs. 0%, p = 0.003), which caused worse progression-free survival (PFS) (log-rank p = 0.0138) and breast cancer-specific survival (CSS) (log-rank p = 0.0076) than non-PABC patients. Tumour stage (III/IV vs. 0/I/II) (HR 16.017, 95% CI 5.830 similar to 44.006, p < 0.001) and endocrine therapy (HR 0.254, 95% CI 0.099 similar to 0.653, p = 0.004) were predictors of PFS. Tumour stage (III/IV vs. 0/I/II) (HR 30.875, 95% CI 7.232 similar to 131.820, p < 0.001), endocrine therapy (HR 0.200, 95% CI 0.049 similar to 0.818, p = 0.025) and targeted therapy (HR 0.143, 95% CI 0.028 similar to 0.743, p = 0.021) were predictors for breast CSS. Among the 15 BCP patients, 11 patients voluntarily continued their pregnancy, and the newborns had no obvious birth defects, either in 5 patients who received chemotherapy or in 6 patients who did not receive chemotherapy during pregnancy. Among the patients who received chemotherapy and did not receive endocrine therapy, 24 PABC patients and 48 non-PABC patients experienced chemotherapy-induced amenorrhea. There was no significant difference in resumption of menstruation between the two groups at 6 months and 12 months after the end of chemotherapy. No potential factors affecting resumption of menstruation were found. Conclusion: Pregnancy at diagnosis or within 1 year after delivery was not a risk factor for a worse prognosis in PABC patients. Compared with non-PABC patients, patients with PABC presented more aggressive tumour characteristics, which could mostly explain the worse prognosis observed in PABC patients. Receiving the appropriate regimen of chemotherapy in the second and third trimesters did not affect the maternal outcomes or neonatal outcomes of BCP patients. The special physiological state during pregnancy and lactation did not interfere with the damage of chemotherapy to ovarian function.