The rate of circumcisions performed on newborn boys in U.S. hospitals dropped 6 percentage points over the last three decades, with an especially steep decline in Western states, according to U.S. government data released on Thursday.
The national rate declined to 58.3 percent in 2010 from 64.5 percent in 1979, according to the report from the National Center for Health Statistics. The tally excludes many circumcisions, including those performed in other places such as religious institutions and those performed later in life.
Broadly, rates fell during the 1980s, increased in the 1990s, and fell again in the early 2000s. During the period covered by the data, male newborn circumcision was most common in 1981, at 64.9 percent, and least common in 2007, at 55.4 percent.
Circumcision is a ritual obligation for infant Jewish boys and is also a common rite among Muslims, who account for the largest share of circumcised men worldwide.
The wider U.S. population adopted the practice due to potential health benefits, such as reducing the risk of urinary tract infections in infants and cutting the risk of penile cancer and sexually transmitted diseases, including HIV.
Still, the practice has been the subject of heated debate, including efforts to ban circumcision in San Francisco and Germany.
The American Academy of Pediatrics said last August that the health benefits of infant circumcision outweigh the risks of the surgery.
The National Center for Health Statistics offered little explanation in the report for the falling rates, but said fluctuations over the years followed changes to the American Academy of Pediatrics' assessment of the procedure's medical value.
The center's findings were based on annual discharge data of between 7,000 and 12,000 newborn boys at between 250 and 550 U.S. short-stay, non-federal hospitals.
In Western states, the rate dropped to 40.2 percent in 2010 from 63.9 percent in 1979, the center said. Rates in the Northeast were flat overall. In the Midwest they mirrored national trends. In the South they increased from 1979 until 1998 and then declined.
A variety of factors could be at work.
The federal Medicaid program for the poor has stopped paying for circumcisions in some 18 U.S. states and some insurers have balked at paying for a procedure without a strong medical justification.
Hospitalization lengths over the decades for mothers and newborns have come to be measured in hours, rather than days, prompting more circumcisions to be done in outpatient settings, said Douglas Diekema, a professor of pediatrics at Seattle Children's Hospital.
The margin of error varies across the data in the report. The national rate, for example, has a relative standard error of roughly 3 percent to 5 percent.