Size Matters in Male Fertility (But Not How You Think)Rebecca Odes
A new study found that when it comes to a man’s fertility, size counts. But it’s not the size of the penis that matters. It’s the size of the perineum, which, in men, is the space between the scrotum and the anus. This area of the body is also known as the “anogenital distance”, and in less biologically and more colloquially inclined circles, as the “taint”.
In what i09 calls “one of the most heroic scientific experiments ever” University of Rochester researcher Shanna Swan measured the anogenital distance (AGD) of 126 men born after 1987. The average distance was two inches, and men with a shorter distance had some significant fertility disadvantages.
A man with a shorter-than-average perineum, Swan found, was 7.3 times more likely to have a low sperm count than a man with a longer-than-average one. Shorter scrotum-to-anus distances were also associated with less well-formed sperm than those emerging from men with longer perineal lengths.
Why would this be? According to the study abstract: “In animals, male AGD (anogenital distance) at birth reflects androgen levels during the masculinization programming window and predicts adult AGD and reproductive function. Our results suggest, therefore, that the androgenic environment during early fetal life exerts a fundamental influence on both AGD and adult sperm counts in humans, as demonstrated in rodents.”
In other words, the distance between the scrotum and the anus may be defined at the same time as the rest of the male reproductive system is growing in utero (AKA “the masculinization programming window”). So a shorter anogenital distance might be a visible indicator of a hormonal issue at the time of male genital development, affecting sperm count and quality later in life.
I’m imagining a whole lot of men contorting themselves with tape measures over this study. But then, they may be used to that.