Rates increased almost twofold in metropolitan Atlanta from 1968 to 1993,
from around 18 per 10,000 births to approximately 40 per 10,000 births. Similarly, rates
increased almost twofold in a national birth defects surveillance system based on hospital
discharge data between 1970 and 1993. Given that rates are about 40 per 10,000 total
births (males and females), they are about 80 per 10,000 male births. Therefore,
almost one per 100 males are born with hypospadias.
The cause of the increase in hypospadias is not known. Original suspicions
were that the increase was due to increasing rates of diagnosis of more mild cases that
were formerly not recorded in medical records. However, the percentage of mild cases in
the Atlanta surveillance system has not increased over the time period. In fact, the
percentage of severe cases has increased over this time period, suggesting that other
explanations should be sought.
In addition to obvious cosmetic problems, boys with untreated hypospadias,
especially the severe type, may have difficulty urinating while standing. Hypospadias is
also often accompanied by a downward bowing of the penis called chordee. It can lead to
difficulties in achieving an effective erection in adulthood. Hypospadias and chordee of
all but the most minor degree are generally corrected surgically in infancy.
For the vast majority of hypospadias cases, no clear cause can be
identified. A small percentage are inherited. Another small percentage may result from the
use of drugs during pregnancy that disrupt the normal sex hormone pathways in the
developing fetus. Rates are highest among whites, lowest among Hispanics, and intermediate
among African Americans.