A new retrospective study provides more evidence that previous breast cancer diagnoses don’t disrupt the health of mothers and newborns in pregnancy: Women who became pregnant at least 12 months after breast cancer diagnosis weren’t more likely than a control group to have preterm births or suffer maternal/neonatal morbidity – even though they were more likely to undergo cesarean section.
“For patients who are more than 1 year out from the diagnosis of breast cancer, it may be safe and reasonable to consider pregnancy without significantly increased odds of maternal or neonatal complications,” said study lead author Kirsten Jorgensen, MD, a gynecologic oncology fellow at the University of Texas Houston School of Public Health, in an interview. “This study does not suggest there is no risk, but it does place the risk that exists in context with the risk that is associated with any pregnancy.”
The study appears in Obstetrics & Gynecology.
The researchers launched the analysis because “there is relatively little data to help guide patients, their oncologists, and their obstetricians as they navigate the potential for pregnancy after a cancer diagnosis,” Dr. Jorgensen said. “There have been prior studies looking at birth outcomes, but they often include people who become pregnant very shortly after diagnosis, which may skew results.”
Researchers used databases to track 30,021 women in California aged 18-45 who were diagnosed with breast cancer from 2000 to 2012. Of those, only 553 met the study criteria and conceived at least 1 year after a stage I-III breast cancer diagnosis (median age at delivery = 36; 50.6% non-Hispanic White, 23.9% Hispanic, 6.0% Black; 83.2% private insurance).
Study authors compared these women to a matched control group of 1,659 women without breast cancer.
After adjustment for various factors, there was no significant difference between the groups in terms of maternal outcomes – preterm birth at less than 37 weeks of gestation (12.5% in the breast cancer group vs. 10.0% in the control group; odds ratio = 1.29; 95% confidence interval, 0.95-1.74) or preterm birth at less than 32 weeks of gestation (1.3% vs. 1.6%, respectively, OR = 0.77; 95% CI, 0.34-1.79).
Researchers didn’t find a significant difference in neonatal outcomes either – small for gestational age (less than the 5th percentile, 3.1% vs. 5.0%, respectively; OR = 0.60, 95% CI, 0.35-1.03; less than the 10th percentile: 9.4% vs. 10%, respectively; OR = 0.94; 95% CI, 0.68-1.30), or neonatal morbidity (8.7% vs. 7.7%, respectively; OR = 1.15; 95% CI, 0.81-1.62).
“It is possible that breast cancer may have little impact because some breast cancer is treated only with surgery or radiation to the chest,” Dr. Jorgensen said. “These treatments likely do not impact fertility and may not impact a developing pregnancy.”
There were neonatal deaths: one in the breast cancer group and four in the control group. The researchers said the small number of deaths limited their ability to interpret the data.
Researchers found no evidence that treatment with chemotherapy affected outcomes. They did turn up a difference between the groups: those who’d had breast cancer were more likely to undergo cesarean delivery (45.6% in the breast cancer group, and 40.1% in the control group; OR = 1.25; 95% CI 1.03-1.53), However, offspring of women in the cesarean group weren’t more likely to have neonatal morbidity (OR = 1.15; 95% CI 0.81-1.62).
It’s hard to explain the higher rate of cesarean deliveries in the breast cancer group, Dr. Jorgensen said. “Overall, among our study population and the matched controls there was a high rate of cesarean section. It is possible there was bias on the provider side. Perhaps they intervened with cesarean section earlier among those with a history of breast cancer – a type of bias due to knowing the history of the patient. We attempted to match for other comorbidities that impact obstetric outcomes, but it is possible that we did not account for all of them.”
In an interview, Patricia A. Ganz, MD, director of cancer prevention and control research at University of California, Los Angeles, praised the new research.
It’s “a well-conducted study with state-of-the-art analysis and interpretation,” she said. “Based on my experience with patients I have cared for with breast cancer, there were no surprises here. Most have had uncomplicated pregnancies. This should be reassuring for women who wish to have children after treatment for breast cancer and clinicians should support this decision.”
As for the higher rate of cesarean delivery in breast-cancer survivors, she said “there may be a tendency to think of these as ‘high risk’ pregnancies, and C-sections may be selected at a more frequent rate as a result.”
The study was funded by the National Institutes of Health, including grants from the National Cancer Institute and the National Center for Advancing Translational Sciences. Dr. Jorgensen has no disclosures. Other authors disclosed advisory board service (Delfina Care) and payments from the NIH, Guidepoint, the Schlesinger Group, and Johnson & Johnson. Dr. Ganz has no disclosures.