PurposeMany studies have shown improved semen parameters after varicocele surgery; however, the benefit in terms of improved pregnancy rates and live births is still disputed in cases of severe oligoasthenozoospermia (OAS). The present study evaluated the outcome of microscopic subinguinal varicocelectomy in terms of the spontaneous pregnancy rate in patients with severe OAS.Materials and MethodsThis was a retrospective, observational, analytic study of 56 men with OAS who underwent microscopic varicocelectomy at our center between 2008 and 2015. The subjects were followed for a mean period of 12.4 months. Outcome was compared among groups of men with mild (sperm concentration, 10.2–19 million/mL), moderate (5.7–9.5 million/mL), and severe (<5 million/mL) OAS who were operated on during the same period.ResultsA total of 13 of 35 men (37.1%) with severe OAS achieved spontaneous pregnancy. Mean sperm density increased from 2.29 million/mL preoperatively to 14.09 million/mL postoperatively. The mean time to pregnancy from the date of surgery was 8.5 months. The spontaneous pregnancy rate in men with mild and moderate OAS was 62.5% and 46.2%, respectively.ConclusionsAlthough pregnancy rates after varicocele surgery are lower preoperatively in men with severe OAS than in men with mild or moderate OAS, the spontaneous pregnancy rate of 37.1% still compares very favorably with outcomes after a single attempt at in vitro fertilization.