The relationship between twin births and maternal risk of breast cancer: A meta-analysis

Hye Sook Kim, Ok Hee Woo, Kyong Hwa Park, Sang Uk Woo, Dae Sik Yang, Ae Ree Kim, Eun Sook Lee, Jae Bok Lee, Yeul Hong Kim, Jun Suk Kim, Jae Hong Seo

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)


Women who undergo a greater number of menstrual cycles may be at increased risk of breast cancer, possibly due to cumulative exposure to ovarian hormones. Pregnancy reduces the lifetime number of menstrual cycles and also influences the levels of ovarian hormones. Twin pregnancies differ from singleton pregnancies in both hormone levels and perinatal changes. To date, a meta-analysis on the effects of twin birth on the risk of maternal breast cancer has not been conducted. Among 17 relevant publications identified in a systematic search, some suggest that twin births may be associated with lower breast cancer risk but others do not; therefore, the results are inconclusive. Although our pooled results of all 17 published studies did not show a reduced maternal risk of breast cancer for twin births (HR 0.94; 95% CI = 0.87-1.02; P = 0.127), a trend toward reduced maternal risk of breast cancer was identified in a subgroup analysis of cohort studies (HR 0.91; 95% CI = 0.83-1.01; P = 0.068). The results of this meta-analysis suggest that twin pregnancy does not significantly decrease the maternal risk of breast cancer.

Original languageEnglish
Pages (from-to)671-677
Number of pages7
JournalBreast Cancer Research and Treatment
Issue number2
Publication statusPublished - 2012 Jan

Bibliographical note

Funding Information:
Acknowledgments This study was supported by a grant of the Korean Healthcare Technology R&D Project, Ministry of Health and Welfare, Republic of Korea (A040151).


  • Breast cancer
  • Meta-analysis
  • Twin births

ASJC Scopus subject areas

  • Oncology
  • Cancer Research


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