Effect of male occupational heat exposure on time to pregnancy.

The relationship between male occupational heat exposure and the time required to achieve a pregnancy [TTP] was studied in a retrospective survey of 402 fertile couples. The TTP for t he subgroups 'exposure t o heat' (median = 4 .0 months; mean 11.8; SD = 13.3) and 'professional driver >3 h/day' (median = 4.5; mean = 14.4; SD = 28.5) was significantly longer (both p < 0.05) than for the controls (median = 2.8; mean = 7.8; SD = 13.3). Bakers and welders showed comparable results: only 14% of the bakers' partners became pregnant within 3 months (cf. 55% of controls, p < 0.05) and only 29% became pregnant within 6 months (cf. 74% of controls, p < 0.02). This study suggests that occupational exposure to heat is a 'weak' risk factor for male subfertility.