Researchers aimed to report on the prognosis, pregnancy outcomes and subsequent ovarian function of pregnancy-associated breast cancer (PABC), which is a rare disease with increasing incidence.

• Researchers assessed data of 63 PABC patients and 126 age-matched non-PABC patients.

• Because of being diagnosed at a more advanced tumor stage (II: 47.6% vs. 45.2%, III: 33.3% vs 19.8%, IV 3.2% vs 0%, p = 0.003), PABC patients had worse progression-free survival (PFS) and breast cancer-specific survival (CSS) compared with non-PABC patients.

• There were 15 patients with breast cancer diagnosed during pregnancy (BCP); 11 of these patients voluntarily continued their pregnancy.

• No obvious birth defects were observed in the newborns, either in 5 patients who received chemotherapy or in 6 patients who did not receive chemotherapy during pregnancy.

• In PABC patients, no risk of worse prognosis was observed in correlation with pregnancy at diagnosis or within 1 year after delivery.

• No effects on the maternal outcomes or neonatal outcomes of BCP patients were evident in correlation with receiving the appropriate regimen of chemotherapy in the second and third trimesters.

• No interference of the special physiological state during pregnancy and lactation was observed with the damage of chemotherapy to ovarian function.