Oxidative DNA damage in human sperm influences time to pregnancy

BACKGROUND: Oxidative stress and related DNA damage in human sperm may be important for fecundity and pregnancy outcome. METHODS: We studied the level of oxidative DNA damage in terms of 7-hydro-8-oxo-2'-deoxyguanosine (8-oxodG) in sperm DNA among 225 first-pregnancy planners. Over the six menstrual cycle follow-up time, after cessation of contraception, 135 pregnancies were conceived. RESULTS: The likelihood of pregnancy occurring in a single menstrual cycle was inversely associated with the 8-oxodG level (P < 0.01). The odds ratio of pregnancy in each of the first three or all six follow-up menstrual cycles was 0.42 (0.23-0.78; 95% CI) and 0.61 (0.36-0.91) per unit increase in the log 8-oxodG/100 000 dG ratio after adjustment for potential confounders, (including sperm concentration) respectively. The intra-individual coefficient of variation of 8-oxodG in 2-6 monthly repeated sperm samples from 116 men was 19% for the 8-oxodG/dG ratio, whereas the inter-individual coefficient of variation was 49%. The 8-oxodG level was not significantly associated with smoking, consumption of alcohol or caffeine, exposure to welding fumes or the plasma levels of sex hormones. CONCLUSIONS: The data suggest that oxidative damage to sperm DNA influences fecundity and the level of damage is relatively constant within an individual and not influenced by smoking.