Maternal Breast Cancer Risk Research Articles

Gender of offspring and maternal breast cancer risk.

A high total number of full-term pregnancies is associated with a reduced risk of breast cancer, though pregnancy transiently increases the risk of the disease. However, little attention has been given to a possible association of breast cancer risk with the gender of offspring, even though male fetuses have been associated with several factors linked to a low breast cancer risk, namely, pregnancy toxemia, increased levels of alpha-fetoprotein (AFP) and increased levels of sex hormone-binding globulin. We used data from linked Swedish registries to study the relative importance of male and female offspring as risk correlates of subsequent breast cancer in the mothers. In a nested case-control study, case patients were 2,328 women who had one or more live-born children delivered between 1973 and 1989 and who were subsequently diagnosed with breast cancer during this period. For comparison, 10,256 control subjects, matched to cases by birth year, were randomly selected from among the eligible women. Number of boys was inversely associated and number of girls positively associated with breast cancer risk. Neither of these trends was significantly different from the null value, but the difference between the 2 trends was marginally significant (p=0.06). Moreover, women who gave birth to 2 or more boys but no girls were at significantly lower risk for breast cancer in comparison to women who gave birth to 2 or more girls but no boys; the odds ratio was 0.78 (95% CI 0.64-0.95). The apparently protective effect of pregnancies with male fetuses was limited to women younger than 40 years. Endocrine or other metabolic processes specifically associated with a male rather than a female fetus may impart relative protection against the occurrence of breast cancer during the childbearing period.

Delivery of premature newborns and maternal breast-cancer risk

During the past fifteen years,two new perspectives have been introduced in the study of reproductive history in relation to breast cancer risk. Lambe and colleagues 1 have provided evidence that a livebirth has dual effects on maternal breast cancer risk—a transient increase followed by a long-term more marked decrease. This observation provided an explanation for what has been thought of as a paradox—that, among young women, parity increases rather than decreases breast cancer risk. 2 In addition, several authors have pointed out that an induced abortion may increase the risk of breast cancer but others have suggested this apparent increase simply reflects a lack of long-term protection that would have been con veyed by a full-term pregnancy. 3,4 Neither of these p e rs p e c t i ves has received biological support from an independent point of view. Because premature deliveries are not accompanied by a late gestational-age hormonal surge, they are likely to modify the dual effect.We have examined in a large population-based database whether premat u r e d e l i ve ries impart less short - t e rm breast cancer ri s k increments and less long-term breast cancer risk reduction in comparison to full-term deliveries. Members of the study cohort were identified from the mothers who delivered liveborn or stillborn babies after a gestation period of at least 28 weeks in Sweden from 1973 to 1989—a total of 1 093 466 women who had a total of 1 953 975 deliveries. However 285 592 women had at least one delivery before 1973 and detailed information on such deliveries was not available.Thus,the study base consisted of 807 874 women whose deliveries occurred after 1973. We used a nested case-control design to allow more efficient analyses. Case patients were women diagnosed with breast cancer during the same period, as ascertained from the records of the National Cancer Registry. For each case patient, five control patients were randomly selected from the study base. These women were individually matched by birth year to the index case, were alive at least to the date of the diagnosis for the index case, and had not been previously diagnosed with breast cancer. Included in the analysis were 2318 breast cancer cases who had complete information on gestation length and had only singleton births. Similarly, 10 199 control women age-matched to the case were available for a n a l y s i s. A premature delive ry is defined as having a gestation age of less than 37 weeks. Age at first birth was adjusted for in all analyses. Among all parous women,having a premature, rather than a term, delivery of their first pregnancy was associated with an overall breast cancer odds ratio of 1·17 (95% CI 0·98–1·40). Premature delivery was not associated with breast cancer risk among women younger than 40 years of age (1·03, 0·79–1·35), whereas it was associated with a significantly increased risk among those aged 40 or older (1·30, 1·02–1·65). Both results are compatible with the previously outlined expectations. Among uniparous women, a premature delivery was associated with a slightly lowered breast cancer risk within 5 years after the delivery compared with a term delivery, whereas it was associated with increased risk later on (table). A similar pattern was evident among multiparous women. The findings of our study indicate that the transient riskincreasing effect of a full-term pregnancy on breast cancer ri s k , which is mostly evident among women in their childbearing years, is less evident after a premature delivery. We have also found that a premature delivery conveys less long-term protection against breast cancer than a term delivery, possibly because it has a more modest impact on the process of terminal differentiation. 5 Our findings suggest that the effect of pregnancy outcomes,including interruption through induced abortion, on maternal breast cancer risk should be examined with variable time lags. They also allow for a coherent view of the complex relation betwe e n reproductive characteristics and breast cancer risk.

Pregnancy Characteristics and Maternal Risk of Breast Cancer

In a population-based case-control study of parous women less than 45 years of age, we evaluated the relations of various pregnancy characteristics to maternal breast cancer risk. Cases (N = 1,239) diagnosed with in situ or invasive breast cancer from 1990 to 1992 in Atlanta, GA, Seattle/Puget Sound, WA, and five counties in central New Jersey, and population controls (N = 1,166) identified by random-digit dialing, were interviewed regarding the details of their pregnancies. We used logistic regression to estimate relative risks (RR) and 95% confidence intervals (CI) and to adjust for breast cancer risk factors. Women who reported nausea or vomiting in their first pregnancy had a slightly lower risk of breast cancer (RR = 0.87; 95% CI = 0.72-1.0). We found no strong or consistent associations for maternal risk related to gestational length, pregnancy weight gain, gestational diabetes, pregnancy hypertension, or gender of the offspring, although we found some evidence for reductions in risk for toxemia (RR = 0.81; 95% CI = 0.61-1.1) and specific sex (RR for female twins vs singletons = 0.48; 95% CI = 0.20-1.3) and timing characteristics of twinning. Overall, these data provide little support for the hypothesis that pregnancy hormone levels are associated with subsequent maternal risk of breast cancer in young women.

Maternal factors and breast cancer risk among young women.

The results from previous studies have provided evidence to support the hypothesised association between intrauterine oestrogen exposure and subsequent risk of breast cancer. Information has not been available to study this relationship for several perinatal factors thought to be related to pregnancy oestrogen levels. Data collected from the mothers of women in two population-based case-control studies of breast cancer in women under the age of 45 years (510 case mothers, 436 control mothers) who were diagnosed between 1983 and 1992 in three western Washington counties were used to investigate further the relationship between intrauterine oestrogen exposure and risk of breast cancer. A pregnancy weight gain of 25-34 pounds was associated with breast cancer risk (odds ratio [OR] = 1.5; 95% confidence interval [CI] 1.1, 2.0); however, women whose mothers gained 35 pounds or more were not at increased risk. Use of antiemetic medication in women with any nausea and vomiting (OR = 2.9; 95% CI 1.1, 8.1) and use of diethylstilboestrol (DES) (OR = 2.3; 95% CI 0.8, 6.4) appeared to be positively associated with breast cancer risk. The results from this study provide limited support for the hypothesis that in utero oestrogen exposure may be related to subsequent breast cancer risk among young women.

Delayed childbearing by education level in the United States, 1969-1994.

Advanced maternal age at first birth, but not at subsequent births, may have detrimental health implications for both mother and child, such as a poor birth outcome and an increased risk of maternal breast cancer. However, positive outcomes may also result such as an improvement in economic measures and offspring's performance on cognitive tests. Research has indicated that women increasingly are delaying their first births beyond the early twenties, but the recent trends in socioeconomic disparity in age at first birth, and the implications for public health, have not been well described. This study used national birth certificate data for 1969-1994 to examine age at first birth by maternal education level. Current Population Survey data were also used to examine changes over time in age and educational distribution among women of childbearing age. Age at first birth increased during the time period. Median age at first birth increased from 21.3 to 24.4 between 1969 and 1994, and the proportion of first-time mothers who were age 30 or older increased from 4.1% to 21.2%. Age at first birth increased rapidly among women with 12 or more years of education; nearly half (45.5%) of college graduate women who had their first birth in 1994 were age 30 or older, compared with 10.2% in 1969. However, little change was observed among women with fewer than 12 years of education; among those with 9-11 years of education, only 2.5% of first births in 1994 occurred at age 30 or older. The trend toward postponed childbearing has occurred primarily among women with at least a high school education. Health services use, such as infertility treatment and cesarean section, may increase as a result of delayed childbearing among higher educated women. Future examinations of the association between maternal age at first birth and health outcomes may need to take greater account of socioeconomic differentials.

Multiple births and breast cancer risk

International Journal of CancerVolume 66, Issue 1 p. 140-140 Research LetterFree Access Multiple births and breast cancer risk Chung-cheng Hsieh, Corresponding Author Chung-cheng Hsieh Cancer Center, University of Massachusetts Medical Center, Worcester, MACancer Center, University of Massachusetts Medical Center, Worcester, MASearch for more papers by this authorDimitrios Trichopoulos, Dimitrios Trichopoulos Department of Epidemiology, Harvard School of Public Health, 677 Huntington Avenue, Boston, MA, USASearch for more papers by this author Chung-cheng Hsieh, Corresponding Author Chung-cheng Hsieh Cancer Center, University of Massachusetts Medical Center, Worcester, MACancer Center, University of Massachusetts Medical Center, Worcester, MASearch for more papers by this authorDimitrios Trichopoulos, Dimitrios Trichopoulos Department of Epidemiology, Harvard School of Public Health, 677 Huntington Avenue, Boston, MA, USASearch for more papers by this author First published: 28 March 1996 https://doi.org/10.1002/(SICI)1097-0215(19960328)66:1<140::AID-IJC24>3.0.CO;2-GAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. References Dietz, A. T., Newcomb, P. A., Storer, B. E., Longnecker, M. P. and Mittendorf, R., Multiple births and risk of breast cancer. Int. J. Cancer, 62, 162– 164 (1995). Hsieh, C.-c., Goldman, M., Pavia, M., Ekbom, A., Petridou, E., Adami, H.-O. and Trichopoulos, D., Breast cancer risk in mothers of multiple births. Int. J. Cancer, 54, 81– 84 (1993). Jacobson, H. I., Thompson, D. W. and Janerisch, D. T., Multiple births and maternal risk of breast cancer. Amer. J. Epidemiol., 129, 865– 873 (1989). Trichopoulos, D., Hypothesis: does breast cancer originate in utero? Lancet, 335, 939– 940 (1990). Volume66, Issue128 March 1996Pages 140-140 ReferencesRelatedInformation

Dual effect of parity on breast cancer risk

This study examined whether breast cancer risk increased for a short period after childbirth, but decreased after a longer period of time. Data from an international case-control study on breast cancer conducted in the 1960s were used to study the modifying effect of age at enrolment on the relationship between parity and breast cancer risk, comparing first uniparous with nulliparous women, and then biparous versus uniparous women. The statistical analysis was performed by modelling through multiple logistic regression, adjusting for study site, age at menarche, menopausal status and obesity index. Comparing uniparous with nulliparous women, an early age at birth seems to be protective for all periods after birth, whereas a late age at birth imparts a higher risk than nulliparity in the period immediately after birth, which declines with the passage of time. The modification effect by age was not apparent when biparous women with different age at second birth were compared with uniparous women. The results support the hypothesis that pregnancy oestrogens impart a transient increase of maternal breast cancer risk when the full-term pregnancy occurs late in a woman's life.

The relation between multiple births and maternal risk of breast cancer.

Data from two case-control studies conducted in New York State during 1982-1986 were used to examine the relation between multiple births and the maternal risk of breast cancer. The cases were 2,561 women between 20 and 79 years of age with a diagnosis of primary breast cancer. Controls (n = 2,616) were selected from driver's license files and matched to cases by year of birth and county of residence. The odds ratio for any multiple birth was 0.94 (95% confidence interval (CI) 0.56-1.56) in women less than 55 years of age and 0.95 (95% CI 0.62-1.46) in women aged 55-79 years. A previous study had shown a multiple last birth to be protective against breast cancer in women less than 55 years of age (odds ratio (OR) = 0.60, 95% CI 0.43-0.85). A decreased risk of breast cancer was also observed for this age group in the present study, but the magnitude of the effect was not as strong and the confidence interval included unity (OR = 0.85, 95% CI 0.43-1.68). A logistic model that controlled for age at first pregnancy, number of live births, age, and county of residence increased the odds ratio to 0.97 for a multiple last birth. The current study does not support an association between multiple births and maternal risk of breast cancer.

Parental age at birth and risk of breast cancer in daughters: a prospective study among US women

We examined the relation between parental age at birth and risk of breast cancer among daughters in a population of 118,309 US women who were 30 to 55 years of age in 1976 and without prior diagnosis of cancer. During 1,140,239 person-years of follow-up, we documented 1,799 incident cases of breast cancer in this population. After adjusting for established breast cancer risk factors, we observed only a weak and nonsignificant trend in risk of breast cancer with increasing maternal age at birth and no relation for paternal age. After adjusting for other risk factors, the chi trend was 1.10, P = 0.27 for increasing maternal age at birth. Daughters born to mothers 30 to 34 years of age had an age-adjusted relative risk of breast cancer of 1.11 (95% confidence interval: 0.89, 1.37) compared to daughters born to mothers less than 20 years of age. The weak positive trend in risk with increasing maternal age was present among both pre- and postmenopausal women. These findings suggest that there is little or no association between maternal age and risk of breast cancer, and that paternal age is not related to risk of breast cancer.

Maternal Age and Breast Cancer Risk

Maternal age at time of birth was investigated as a risk factor for breast cancer in a study of 1,176 matched case-control pairs. There was no pattern of increasing adjusted relative risk of breast cancer with increasing maternal age, nor was the mean maternal age of cases older than that of controls. Similar negative results were found among the subset of subjects up to 35 years old, a group previously found to show marked maternal age effects. Thus previous reports of an association between breast cancer and advanced maternal age may have been due to chance, extraneous factors, or a misleading reliance on unadjusted mean maternal ages, rather than on relative risks.