Between 2006 and 2012 there was a decline in episiotomy, which is a surgical procedure in which the birth canal is surgically widened in order for the mother to have an easier birth.

The common procedure is estimated to be performed in 25 percent of all vaginal births in the U.S., a news release reported, but the procedure has unclear benefits.

To make their findings the researches looked at 2,261,070 women who were hospitalized for a vaginal delivery in 510 hospitals, of whom 325,193 underwent episiotomy (14.4 percent). The team observed a decline in the rate of episiotomy between the years of 2006 and 2012; during this time period the rate dropped from 17.3 percent to 11.6 percent.

There were several demographical factors that were found to influence the rate of episiotomy: "5.7 percent of white women vs. 7.9 percent of black women; and 17.2 percent with commercial insurance vs. 11.2 percent with Medicaid insurance," the researchers reported,

The data was taken from the Perspective database to identify women who underwent a vaginal delivery between 2006 and 2012. The database included more than 500 hospitals, which is about 15 percent of the national hospitals that include deliveries.

Hospital factors such as location and teaching status were also found to have an influence on more or less episiotomy use.

"These observations suggest nonmedical factors are related to use of episiotomy," the authors write.

The researchers noted that among the 10 percent of U.S. hospitals that used the procedure most frequently the average adjusted hospital episiotomy rate was 34.1 percent as opposed to 2.5 percent seen in the hospitals that were least likely to turn to the procedure.

The findings were published in a recent edition of the JAMA Network Journals.