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Birth weight and risk of renal cell cancer.

BACKGROUND
The prenatal period has been suggested to be important for future cancer risk. Conditions in utero are also important for the development of the kidney, and birth weight, a marker of fetal nutrition and growth, is linearly correlated with the number of nephrons and the structural and functional unit of the kidney. An association between birth weight and renal cell cancer, the major form of kidney cancer, is biologically plausible, but has never been studied.


METHODS
We conducted a population-based, case-controlled study in Sweden of men and women aged 20 to 79 years. We collected self-reported information on categories of birth weight from 648 patients with newly diagnosed renal cell cancer and from 900 frequency-matched control subjects. We used unconditional logistic regression to calculate odds ratios (ORs) and 95% confidence intervals (CIs) as estimates of the relative risks.


RESULTS
An increased risk of renal cell cancer was observed among men with a birth weight of > or =3500 g (adjusted OR = 1.3, 95% CI, 1.0 to 1.8) compared with men with a birth weight between 3000 and 3499 g, especially in the subgroup without hypertension or diabetes (adjusted OR = 1.8, 95% CI, 1.2 to 2.6). No clear association among men with a birth weight <3000 g or among women was found.


CONCLUSIONS
Our study shows that conditions in utero, reflected by birth weight, might affect the risk of renal cell cancer in adulthood. It is unclear why no association was found among women. Further studies, based on weight from birth certificates, are needed to clarify this relationship.