Background
Prenatal exposures to xenobiotics during the masculinization programming window are suggested to impact male fecundity later in life. Frequently used nitrosatable drugs, such as penicillins and beta2-agonists, contain amines or amides that may form teratogenic compounds in reaction with nitrite.

Objectives
We explored whether maternal nitrosatable drug use during gestation was associated with biomarkers of male fecundity in adulthood; moreover, the potential modifiable effect of nitrate and vitamin intake was investigated.

Method
We performed a cohort study in the Fetal Programming of Semen Quality cohort that includes semen characteristics, reproductive hormone concentrations, and measures of testis size on 1058 young adult sons in the Danish National Birth Cohort. Information on maternal use of nitrosatable drugs was obtained from questionnaires and interviews around gestational weeks 11 and 16. A multivariable negative binomial regression model was used to obtain relative differences in biomarkers of male fecundity for those whose mothers used nitrosatable drugs compared to those without such maternal use. In sub-analyses, the exposure was categorized according to nitrosatable drug type: secondary amine, tertiary amine, or amide. We investigated dose dependency by examining the number of weeks with intake and explored potential effect modification by low versus high maternal nitrate and vitamin intake from diet and nitrate concentration in drinking water. We added selection weights and imputed values of missing covariates to limit the risk of selection bias.

Results
In total, 19.6% of the study population were born of mothers with an intake of nitrosatable drugs at least once during early pregnancy. Relative differences in biomarkers related to male fecundity between exposed and unexposed participants were negligible. Imputation of missing covariates did not fundamentally alter the results. Furthermore, no sensitive subpopulations were detected.

Conclusions
The results suggest that maternal use of nitrosatable drugs does not have a harmful influence on the male fecundity of the offspring.