Coffee drinking during pregnancy may affect son's sex hormone levels.

Oct 05, 2008

Ramlau-Hansen, CH, AM Thulstrup, JP Bonde, J Olsen and BH Bech. 2008. Semen quality according to prenatal coffee and present caffeine exposure: two decades of follow-up of a pregnancy cohort. Human Reproduction online August 28.

Synopsis by Kim Harley, Ph.D.

Adult men may have lower testosterone levels if their mother drank large amounts of coffee during pregnancy.

Adult men whose mothers drank more than seven cups of coffee a day when pregnant had lower levels of testosterone and other sex hormones than men with lower prenatal exposure to the brew. This is the first study to examine the long-term effects of prenatal coffee and caffeine exposure on human male reproductive health.

Caffeine is known to cross the placenta and affect the fetus during pregnancy. Animal studies show that prenatal exposure to caffeine metabolites changes testicular development; however, in this study, what caused the effects - whether the caffeine or something else in the coffee - was not clearly identified. This new study from Denmark finds that the adult sons whose mothers drank large amounts of coffee during pregnancy had testosterone levels almost 10% lower than those whose mothers drank none to three cups of coffee per day. Lower levels of the hormone inhibin B and lower semen volume were also seen among men with high prenatal coffee exposure, although the results were not statistically significant. In addition, the men's current caffeine consumption was examined in relation to their testosterone levels.

The researchers found that higher caffeine intake was associated with higher testosterone levels, a finding supported by other studies. These opposite results illustrate how similar exposures occurring at different times of life, in this case fetal versus adult exposure, can render different effects. The study was small, with only 343 men enrolled, and the amount of coffee consumed by mothers was high. The men were sons of women who were enrolled in a pregnancy study between 1984 and 1987. The mothers reported their coffee intake during the pregnancy. The results of this preliminary study suggest that further research is warranted to fully understand the long-term impacts of high exposures during development.