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Since registration started in the 1950s, the incidence of testicular cancer (TC) in the Western world has increased, which is also the case in Norway. Men born in Norway during World War II (WWII), however, have a lower TC incidence than men born in the years before or after WWII. Increased fetal exposure to estrogen during the first trimester of pregnancy has been proposed as a risk factor for the development of TC later in life. Increased maternal weight is associated with higher insulin levels, leading to lower sex hormone-binding globulin levels and thereby increased levels of bioavailable estrogens for transplacental transfer from mother to fetus. The aim of the present study was therefore to examine whether there was an association between maternal weight and the incidence of TC among those who were born in a time period where the nutritional conditions changed,i.e., around the time of WWII. We compared data for a random sample of women giving birth in Oslo, Norway, in the years 1931 to 1955 with the TC incidence among men born in the whole country in the same time period. Maternal weight at delivery was used as a proxy for first-trimester weight. We found a correlation (Spearman's rho = 1.00,p< 0.01; Pearson's r = 0.95,p= 0.02) between the TC incidence and maternal weight adjusted for birth weight and maternal age. Although one cannot draw firm conclusions from ecologic correlations, these findings suggest that the increase in TC incidence over the past decades could be at least partly attributed to the increased maternal body weight observed in most populations in the relevant time period since TC is thought to be associated within uteroconditions.