Breast cancer, pregnancy, and breastfeeding

J Obstet Gynaecol Can. 2002 Feb;24(2):164-80; quiz 181-4.
[Article in English, French]


Objective: The primary objective of this guideline is to provide Canadian physicians up-to-date, accurate information and recommendations regarding: i) impact of pregnancy and lactation on risk of breast cancer; ii) prognosis of breast cancer diagnosed during pregnancy and lactation; iii) risk of recurrence of breast cancer with the occurrence of subsequent pregnancies; iv) feasibility of breastfeeding and its impact on the prognosis of women with breast cancer.

Options: This guideline reviews evidence on whether pregnancy and breastfeeding change the lifetime risk for breast cancer in women, and whether breast cancer diagnosed during pregnancy or during lactation has a different prognosis. It offers the clinician advice on the diagnostic options to help identify breast cancer in pregnancy and/or during lactation, and offers evidence-based recommendations in managing an ongoing pregnancy and/or lactation when treatment for breast cancer is being planned. It also offers recommendations to clinicians in counselling their patients regarding future pregnancy and future breastfeeding for women who have been treated for breast cancer.

Outcomes: These guidelines should help physicians counsel patients using evidence-based recommendations. These recommendations may also improve the prognosis of patients diagnosed with breast cancer during pregnancy and lactation, or of those patients who had breast cancer and are contemplating future pregnancies.

Evidence: A Medline search was carried out for all publications from 1990 through 2000, in the English language, related to breast cancer and pregnancy in terms of diagnosis, prognosis, and treatment, as well as for breast cancer and breastfeeding, with particular focus on impact of treatment of breast cancer on lactation and prognosis of breast cancer after lactation. The authors submitted the manuscript for review to members of the Breast Disease Committee, who also validated the levels of evidence. The final manuscript was submitted to the SOGC Council for approval and dissemination. The levels of evidence for recommendations have been determined using the criteria described by the Canadian Task Force on the Periodic Health Examination.

Benefits, harms, and costs: Canadian physicians will be able to counsel their patients on the impact of pregnancy and lactation on a woman's lifetime risk for breast cancer. Physicians and patients will be empowered to decide how to manage pregnancy and lactation when breast cancer is diagnosed in pregnancy, and to appreciate the ramifications of reproduction and breastfeeding after breast cancer. This guideline identifies areas where good evidence is lacking and advocates research in those areas.

Recommendations: Women should be counselled regarding their risk for breast cancer and be informed that: 1. There is good evidence that there is a transient increase in risk of breast cancer in the first three to four years after delivery of a singleton baby (II-2B). Subsequently, their lifetime risk seems lower than that of women who remain nulliparous (II-2B). 2. There is good evidence that the risk for premenopausal breast cancer is reduced with lactation (II-2A). This protective effect seems to be best for women who had extended periods of breastfeeding during their lifetime (ll-2B). Women with familial risks could potentially benefit most from breastfeeding (II-2C). Since breast milk is the ideal nutrient for the newborn, and since breastfeeding is a modifiable risk factor, all women should be encouraged to breastfeed their children (II-2A). 3. All women should be encouraged to practice breast self-examination in pregnancy and during lactation (II-2B). Clinicians should screen all pregnant patients for breast cancer with thorough breast examination early in pregnancy (III-B). The clinician is advised to examine the breast in the postpartum period if the woman is not breastfeeding. The obstetrician is advised to examine the breast at any time in the postpartum period if the woman presents with breast symptoms (III-B). 4. Physicians should be encouraged to use ultrasltrasonography, mammography, needle aspiration, or breast biopsies to assess suspicious breast masses in pregnancy and during lactation, in the same timely fashion as for non-pregnant or non-lactating women (II-2A). Interruption of lactation during investigation is not necessary, nor is it recommended unless nuclear studies are entertained (III-B). 5. Once breast cancer is diagnosed, a multidisciplinary approach should be taken. This includes the obstetrician, surgeons, medical and radiation oncologists, and breast cancer counsellors (II-2A). 6. In early pregnancy, the patient should be counselled regarding the effect of proposed therapy on the fetus and on overall maternal prognosis. Termination of pregnancy should be discussed, but the patient should be counselled that prognosis is not altered by termination of pregnancy. Women should be advised that premature menopause may result from breast cancer treatments, especially if chemotherapy is given to patients who are past the age of 30. (II-2C) 7. Up until now, modified radical mastectomy was the cornerstone of surgical treatment of breast cancer during pregnancy. Adjuvant chemotherapy should be entertained and, if required, administered without delay. The patient should be counselled regarding the effect of chemotherapy on the fetus and/or the future reproductive potential of the patient (II-2B). In the third trimester, the risks and benefits of early delivery versus continuation of pregnancy, and the effect of chemotherapy on the fetus, should be addressed (II-2B). Women undergoing chemotherapy or tamoxifen treatment should not breastfeed (III-B). 8. Women treated for breast cancer and who wish to become pregnant should be counselled that pregnancy is possible and does not seem to be associated with a worse prognosis for their breast cancer (II-3C). However, they should be made aware that the evidence to support such advice is relatively poor. 9. Since most breast cancer recurrences appear within two to three years after initial diagnosis, patients should be advised to postpone pregnancy for three years (III-C). If a patient has axillary node involvement, the recommendation to defer pregnancy should be extended to five years, but this recommendation is based on opinion only (III-C). Prior to attempting pregnancy, a breast cancer survivor should be referred for a full oncologic evaluation. 10. There is no evidence that breastfeeding increases the risk of breast cancer recurring or of a second breast cancer developing, nor that it carries any health risk to the child. Women previously treated for breast cancer, who do not show any evidence of residual tumour, should be encouraged to breastfeed their children (III-B).

Validation: Level of evidence, quality of research in the recruited publications, and ensuing recommendations were reviewed and discussed by members of the SOGC Breast Disease Committee as well as by a member of the Gynaecological Oncology Committee. External reviewers with expertise in the area were also solicited for comments and criticism.

Publication types

  • Guideline
  • Practice Guideline

MeSH terms

  • Breast Feeding*
  • Breast Neoplasms / etiology*
  • Breast Neoplasms / therapy*
  • Evidence-Based Medicine
  • Female
  • Humans
  • Lactation*
  • Medical Oncology / standards
  • Obstetrics / standards
  • Parity
  • Patient Education as Topic
  • Pregnancy
  • Pregnancy Complications, Neoplastic / etiology*
  • Pregnancy Complications, Neoplastic / therapy*
  • Pregnancy Outcome*
  • Prognosis
  • Research Design
  • Risk Factors