Birth characteristics in men with infertility.

Research question: Are low birth weight, prematurity, being born small for gestational age, or both, associated with a higher risk of male factor infertility in adulthood? Design: Retrospective study of a clinical sample of 892 men, diagnosed with an infertility factor (male, female, combined or unexplained) together with their female partner at a University Hospital clinic in Sweden between 2005 and 2010. Data on birth weight and gestational age at birth were retrieved from the Swedish Medical Birth Register. The distribution of non-optimal birth characteristics in relation to infertility factor was described. A control group was created consisting of two men for each index man, born in Sweden in the same year as each index men, as well as a reference group consisting of all men born in Sweden the same years. Results: The likelihood of having been born small for gestational age was almost fivefold higher in men with male factor infertility than in men with unexplained infertility (OR 4.84, 95% CI 1.32 to 1780). Men with male factor infertility were more often born with non-optimal birth characteristics than the control group (14.8% versus 8.5%; P = 0.010) and the reference group (14.8% versus 11.4%; P < 0.001). Men with azoospermia were more often born with non-optimal birth characteristics, compared with men without azoospermia (21.3% versus 12.1%; P = 0.038). Conclusions: The results suggest an association between intrauterine growth restriction and male factor infertility in adulthood.