Risk of infertility
Men who previously had bilateral cryptorchidism have greatly reduced fertility compared to those who had unilateral cryptorchidism and those of the general male population.
Lee et al showed a paternity rate of 62% (38% infertile) in those with bilateral cryptorchidism compared to a matched control group (rate of 94%, ie, 6% infertile), indicating a 6-times increased risk. In contrast, men with unilateral cryptorchidism had a paternity rate of 89.5%. Although this represents a 2-fold increase in infertility, this rate is similar to the level of infertility found in other studies of the general population.
Examination of subfertility, or time to pregnancy, shows that with bilateral cryptorchidism, men have greatly increased waiting times to pregnancy (33.9 mo vs 11.1 mo for those with unilateral cryptorchidism and controls). Lee, Coughlin, and Bellinger also examined the association of pretreatment testis location with fertility rates and various hormone levels (inhibin B, LH, FSH, testosterone) in adulthood. They concluded, "preoperative testis location in men with previous unilateral cryptorchidism is not a major determinant of fertility according to paternity, sperm count, or hormone levels."
Although semen quality may be impaired in men with a unilateral cryptorchid history, the correlation between semen analysis results that indicate impairment, decreased fertility index (number of spermatogonia per 50 tubules), and paternity has been poor. Thus, paternity may be a more useful indicator of fertility in these patients
Hope this helps... FYI- Not sure if you know, but cryptorchidism is an undescended teste, unilateral is one side and bilateral is both. You've probably read all about it. I found this info at
http://www.emedicine.com/med/topic2707.htm near the bottom of the page. I'll keep looking...
Tracy