For years, conventional wisdom and medical advice said pregnancy after breast cancer could lead to cancer returning. In this analysis of studies over 40 years, an international research team found that pregnancy is safe for women with a history of breast cancer and does not hurt overall survival.
The study, published in the European Journal of Cancer, also looked at related issues, including why some research has shown a possibly protective effect of pregnancy.
Reason for Study
With many postponing pregnancy until they are older, more women could be diagnosed with breast cancer while still wanting to have children.
Levels of the hormone estrogen are very high during pregnancy. Many breast cancers have estrogen receptors, and the length of estrogen exposure may be related to breast cancer incidence. For that reason, some women affected by breast cancer are told to avoid becoming pregnant, or fear having a pregnancy.
Yet there is no “strong supporting evidence” to show that pregnancy is unsafe, say the authors of this study. They undertook this analysis to find out if becoming pregnant after breast cancer affects overall survival.
The researchers included 14 studies in their analysis. They looked at data on 1,244 women who became pregnant after breast cancer and compared them to a control group of 18,145 women who did not become pregnant after diagnosis. The researchers also used unpublished statistics from some studies to gain more details.
Each woman in the control group was matched with a pregnancy group woman. Some control group women had survived at least as long as their counterparts before becoming pregnant. Others survived without a breast cancer recurrence for that same time. Most of the included studies analyzed overall survival for at least 10 years.
Overall, the study suggested pregnancy is safe after breast cancer. It also showed that women who became pregnant after breast cancer had a significantly lower risk of death than those who did not.
The latter finding suggests pregnancy protects women from recurrence. But the differences between groups could be due to the healthy mother effect, or when women with earlier stage cancers, who have a lower risk of recurrence, may be encouraged by their doctors to become pregnant (and do), while women with more aggressive cancers may be advised against it (and do not).
To remove the influence of healthy mother effect, the researchers analyzed a smaller control subgroup whose cancer had not returned. That analysis found that overall survival for women who became pregnant after breast cancer was not significantly better than for women who did not become pregnant.
To see whether pregnancy’s hormonal changes might affect women with ER+ cancers, several of the authors and others conducted a later study of 333 women, presented at the 2012 European Breast Cancer Conference. They found no difference in the length of survival without cancer return between women with ER+ and ER- diagnoses following pregnancy.
What This Means for You
This study demonstrates the long-term safety of pregnancy. Other studies have shown higher recurrence rates for women who become pregnant less than two years after diagnosis. For that reason, the authors suggest waiting two years before trying to conceive. They also advise women with estrogen receptor-positive (ER+) breast cancer to complete the recommended five years of hormonal therapy (tamoxifen) after primary treatment before attempting pregnancy.
If you want to become pregnant, it may reassure you to know pregnancy is safe to consider after breast cancer. Make sure your doctor clears you before you start trying.
Talk with your providers soon after diagnosis or early in your care. Here are questions to ask:
- What can be done to preserve my fertility for a later pregnancy?
- How long will my breast cancer treatment last?
- When after treatment will I be able to start trying to get pregnant?
- Can I take a “time out” from treatment to conceive and have a baby?
Even if your treatment is over, talk with your doctor to see what options you might have. Learn more in LBBC’s Ask the Expert: Fertility and Pregnancy.
HA Azim Jr., L Santoro, N Pavlidis, S Gelber, N Kroman, H Azim, FA Peccatori. Safety of Pregnancy Following Breast Cancer Diagnosis: A Meta-Analysis of 14 Studies. Eur J Cancer 2011;47(1):74-83.
This article was supported by Cooperative Agreement Number DP11-1111 from The Centers for Disease Control and Prevention. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the Centers for Disease Control and Prevention.