Nearly one in every 25 children is born before the medically approved date, according to a new study conducted by the Children's hospital of Philadelphia and University of Minnesota School of Public Health.

Researchers said that a considerable number of babies are delivered through elective cesarean sections and elective induced labor. The study emphasizes established recommendations by medical and public health organizations against early deliveries without appropriate medical reasons.

Scott A. Lorch - M.D., M.S.C.E., a neonatologist at The Children's Hospital of Philadelphia (CHOP) - said that previous studies showed poorer health outcomes for infants born before 40 weeks gestation when compared to full-term births.

"Unfortunately, many of these earlier births are 'nonindicated,' meaning there is not a medical rationale to deliver the baby early. We analyzed the extent to which these infants are born too soon and without medical indication," Lorch said in a press release.

For the study, the researchers examined 7.3 million uncomplicated term births between 1995 and 2009 in California, Missouri, and Pennsylvania.

The researchers found that the early-term non-indicated birth rate was 3.18 percent during the study period. The rate peaked in 2006, where four percent of uncomplicated births occurred before 39 weeks of pregnancy without medical indication. The rate fell to 3.74 percent, which is 86 percent higher than it was in 1995.

"Our study showed that early elective deliveries are making up between 3 and 4 percent of U.S. births each year. This may seem to be a small number, but with 4 million births a year in the U.S., each percentage point represents 40,000 babies," said Lead author Katy B. Kozhimannil, Ph.D., MPA, of the University of Minnesota School of Public Health.

The finding is published in the journal Medical Care.