Pregnancy Safe in Those Who Previously Had BC in Pregnancy

Women diagnosed with breast cancer during a pregnancy were no more likely to experience disease recurrence or shortened survival after a subsequent pregnancy within the next 7 years than women who did not become pregnant again, according to new research.

Marta Perachino, MD, a medical oncologist at Vall d’Hebron Institute of Oncology in Barcelona, Spain, presented this and other findings of the international retrospective study at the ESMO Breast Cancer 2025 in Barcelona, Spain.

“Our findings may help in the reproductive counseling of young BRCA carriers wishing to have a subsequent pregnancy after a prior diagnosis of breast cancer during pregnancy,” Perachino told attendees during her presentation.

Multiple past studies have shown that women with a history of breast cancer can safely carry a pregnancy without an increased risk for recurrence, even among BRCA carriers, but Perachino noted the lack of data on the safety of a subsequent pregnancy in those who received their breast cancer diagnosis during pregnancy.

Methods and Results

The researchers conducted a retrospective cohort study with the BRCA BCY Collaboration, which involved 6236 registered patients from 109 centers across 33 countries. They identified women aged 40 years and younger who were diagnosed during pregnancy with invasive breast cancer between January 2000 and December 2020 and had a pathogenic or likely pathogenic variant of BRCA1 or BRCA2. Women with a history of ovarian cancer or other malignancies were excluded, as were those diagnosed with stage IV de novo breast cancer and those diagnosed postpartum.

Among 282 BRCA carriers in the cohort diagnosed with breast cancer during pregnancy, 68 (24.1%) had had a subsequent pregnancy at a median 7 years of follow-up. These patients were younger at diagnosis (median age, 31 years) than the 214 patients without a subsequent pregnancy, who were a median age of 34 years at diagnosis (P < .001).

More of the women who became pregnant after the pregnancy when they were diagnosed had had a hormone receptor−negative (HR−) cancer (79%) compared with those without a subsequent pregnancy (60.3%; P = .029). Only 21% of the women with a subsequent pregnancy after the one with a diagnosis had had HR+ cancer. Patients with and without a subsequent pregnancy did not otherwise differ in terms of their specific BRCA variant, tumor size, nodal status, grade, or human epidermal growth factor receptor 2 status.

Nearly all the women diagnosed during a past pregnancy had received chemotherapy (96.1%), mostly anthracycline- and taxane-based (76%) therapy and endocrine therapy (91.6%), primarily tamoxifen alone (39.1%), tamoxifen with a luteinizing hormone−releasing hormone (LHRH) agonist (21.1%) or an aromatase inhibitor with LHRH (20.7%). Those with and without a subsequent pregnancy did not significantly differ in the treatment regimens they received.

A Kaplan-Meier estimate of the cumulative incidence of pregnancy over 10 years of follow-up in the overall cohort, taking into account likely future pregnancies based on the rate at a median 7 years of follow-up was 36.6% (95% CI, 29.5%-44.8%).

Disease-free survival over a median 7 years of follow-up was not significantly different for women who had a subsequent pregnancy after the one with their diagnosis compared with those who did not have a subsequent pregnancy (adjusted hazard ratio [aHR], 1.06; 95% CI, 0.49-2.31; P = .875), after adjustment for their specific BRCA variant, their year and age of diagnosis, and their hormone receptor status. Overall survival was also similar in those women with a subsequent pregnancy compared with that in those without one (aHR, 0.63; 95% CI, 0.19-2.05; P = .444).

Among those with a subsequent pregnancy, the median time from diagnosis to conception of the subsequent pregnancy was significantly longer in those with HR+ cancer (4.4 years) than in those with HR− cancer (3 years; P = .027). The interval between pregnancies was also longer among those with HR+ cancer than in those with HR− cancer: 35.7% of pregnancies in HR+ patients occurred more than 5 years after the previous pregnancy compared with 7.6% of pregnancies in patients who are HR− (P = .021).

Pregnancy Outcomes Matched Expectations for General Population

The women were an average of 34 years old at the time of their subsequent pregnancy, and two thirds (67.6%) had a spontaneous pregnancy, while 16.2% had used assisted reproductive technology. The miscarriage rate (11.8%), preterm birth rate (14.8%), rate of congenital anomalies (1.9%), and rates of delivery, pregnancy, or fetal complications were all in line with expected rates in the general population. Breastfeeding was reported by 61.1% of the women, with no data available from 31.5% of them.

There were 1.65 distant relapse events per 100 person-years among those with a subsequent pregnancy compared with 2.62 per 100 person-years in those without. Locoregional relapse occurred at a rate of 0.99 per 100 person-years in those with a subsequent pregnancy and a rate of 1.64 per 100 person-years in those without one. Second primary breast cancer rates were also similar in those with (1.65 per 100 person-years) and without (1.35 per 100 person-years) a subsequent pregnancy. A subgroup analysis of disease-free survival showed no differences between groups based on BRCA variant, nodal status, or hormone-receptor status.

Despite the small population of patients with a subsequent pregnancy, the study’s strengths included its reliance on an international network and its unique population of young women with a BRCA mutation, said Stefano Spinaci, MD, of the Department of Breast Surgery at Ospedale Villa Scassi ASL3 in Genova, Italy, who was invited to discuss the findings after the presentation.

While there were no evident concerns about maternal outcomes through the median 7 years of follow-up and preterm delivery and congenital anomaly rates were similar to rates in the general population, the majority of the patients (80%) had HR− disease, he noted. Further, the study does not include data on the effect of the newest treatments, such as olaparib and pembrolizumab, he pointed out.

“Pregnancy after the breast cancer, including when diagnosed during a previous pregnancy in BRCA carriers, is safe, but careful planning is essential, especially in those with hormone receptor−positive disease,” Spinaci said. “Last, but most important, we have to encourage [clinicians] to offer personalized, multidisciplinary reproductive counseling to all young women diagnosed with breast cancer, starting from the time of diagnosis.”

The research was funded by the Italian Association for Cancer Research. Perachino and Spinaci had no disclosures.

Tara Haelle is a science/health journalist based in Dallas.