An increased risk of breast cancer after delayed first parity.
BACKGROUND
As delayed childbirth increases for socioeconomic and fertility reasons, its impact on breast cancer risk needs definition.


METHODS
From 1975 to 1981, 1307 women with childbirth at >or=40 years of age were identified. They were divided into four groups by estimated first birth median ages (EFBMA): 23, 34, 38, and 41 years, corresponding to previous parity of more than 3, 2 or 3, 1, and zero, respectively. Cancer Registry cross-referencing identified those diagnosed with breast cancer.


RESULTS
Breast cancer developed in 39 women. The EFBMA of 41 years carried a relative risk of 3.7, (95%CI: 1.30 to 10.5) compared with age 23. Odds ratio of breast cancer was 1.08 (95%CI: 1.02 to 1.14) with each year older at first birth and 0.79 (95% CI: 0.67 to 0.93) for each additional previous birth.


CONCLUSIONS
Increased breast cancer risk with advancing maternal age at first childbirth is supported by 3.7 relative risk in women with an EFBMA of 41 years compared with those with an EFBMA of 23 years.
Lee
Susan H
SH
The Breast Health Center, Program in Women's Oncology, Women and Infants' Hospital of Rhode Island, Brown University School of Medicine, Providence, RI, USA.
Akuete
Kwei
K
Fulton
John
J
Chelmow
David
D
Chung
Maureen A
MA
Cady
Blake
B
D000328:Adult; D001943:Breast Neoplasms / Q000209:etiology*; D005260:Female; D006801:Humans; D008423:Maternal Age; D010298:Parity; D018566:Pregnancy, High-Risk; D012307:Risk Factors