Gender of offspring and maternal risk of invasive epithelial ovarian cancer

Harvard University, Cambridge, Massachusetts, United States
Cancer Epidemiology Biomarkers & Prevention (Impact Factor: 4.13). 11/2007; 16(11):2314-20. DOI: 10.1158/1055-9965.EPI-07-0645
Source: PubMed


Gender of a fetus is associated with maternal hormonal milieu and may therefore modify maternal risk of ovarian cancer following a birth. We evaluated the relation between gender of offspring and maternal risk of epithelial ovarian cancer in a large case-control study nested within a nationwide cohort. Cohort members were identified in the Swedish Fertility Register. Cases of invasive epithelial ovarian cancer were identified in the Swedish National Cancer Register from 1961 to 2001. Five controls were matched by age to each case. A total of 7,407 cases and 37,658 controls with only singleton births were included in the analysis. We fit logistic regression models to study the association between gender of offspring and ovarian cancer risk, controlling for covariates. Maternal risk of ovarian cancer was reduced with increasing numbers of male offspring and increased with number of female offspring. Compared with women who gave birth to only girls, multivariate odds ratios (95% confidence interval) of invasive epithelial ovarian cancer were 0.92 (0.87-0.98) for those who gave birth to one boy, 0.87 (0.80-0.94) for two boys, and 0.82 (0.73-0.94) for three or more boys (P value test for trend <0.001). There was a positive but nonsignificant association with number of girls. Similar results were observed when restricting the analysis to women born before 1935. Our findings suggest that hormonal and physiologic conditions in pregnancy with male, but not with female, offspring are associated with a lowered maternal risk of invasive epithelial ovarian cancer.

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Available from: Anders Ekbom, Oct 05, 2015
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    • "Strengths of our study include the population-based nature of the study, the large sample size, and histologically verified cases. With the large number of subjects, analyses of data from this study have been able to identify the postpartum period when the risk of maternal ovarian cancer is at its lowest [18] and examine the effect of offspring gender on the risk of maternal ovarian cancer [29]. There are potential limitations. "
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    ABSTRACT: Pregnancies reduce the risk of ovarian cancer, and among multiparous women, levels of circulating progesterone might be higher during pregnancies with wider birth spacing. We hypothesized that childbirth with wider birth spacing might reduce maternal risk of invasive epithelial ovarian cancer more than births with narrower spacing. We conducted a case-control study nested in a nationwide cohort of Swedish women from 1961 to 2001. We selected five individually age-matched controls for each case of invasive epithelial ovarian cancer, and analysis for the effect of birth spacing was performed for 5,341 cases and 29,047 controls. We applied unconditional logistic regression analyses adjusting for age, ages at childbirth, educational level, area of residence, and gender of offspring. Relative risk of invasive epithelial ovarian cancer associated with each one-year increase in average birth spacing is 1.00 (95% CI = 0.98-1.01) among all women and 0.99 (0.98-1.01) among those born before 1935 and less likely to have used oral contraceptives. Further analyses on the biparous and triparous women did not find a consistent association between birth spacing and the risk of ovarian cancer. Birth spacing is unlikely to be a major determinant underlying the protective effects of childbirth on ovarian cancer risk.
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