A Trial to Compare Efficacy and Safety of Follitropin Delta Versus Placebo (Inactive Treatment) in the Treatment of Men With Idiopathic Infertility (Unexplained Reduction of Semen Quality) (ADAM)

Inclusion Criteria: * History of infertility with current partner at randomisation must be 12-60 months if current partner is aged \<35 years or 6-60 months if current partner is aged 35-38 years. * Men between the ages of 18 and 50 years. * Total sperm count 5-39 million at screening; confirmed by two consecutive samples taken ≥2 weeks apart before randomization. * Total sperm motility of ≥10% at screening; confirmed by two samples taken ≥2 weeks apart before randomisation. If a semen sample has been taken within 3 months prior to screening and been analysed at an andrology laboratory, it can be included as the first of the two semen samples at screening. * Semen volume ≥1.4 mL at screening; confirmed by two consecutive samples taken ≥2 weeks apart before randomization. * Serum follicle-stimulating hormone (FSH) levels of 2-12.0 IU/L (measured at central laboratory) at screening) * Serum luteinising hormone (LH) levels of 1.2-7.5 IU/L (measured at central laboratory) at screening. * Serum total testosterone levels of ≥300 ng/dL (equals ≥10.4 nmol/L; measured at central laboratory) at screening. * Agree to have regular intercourse with current female partner with the intent of spontaneous conception within 9 months from randomization. * Agree to provide information on female partner's positive urine pregnancy test(s) and documentation of ultrasound(s), delivery, and neonatal/infant health. Current partner fulfilling the criteria below: * Pre-menopausal woman between the ag…