A study shows that the percentage of underweight or premature newborn babies has increased over the last seven years.

According to the results of a study by Doctor Kim Min-hee at Konkuk University Hospital, infants weighing less than 25-hundred grams accounted for four-point-four percent of newborn babies in 2006, up from three-point-eight percent in 2000.

The total number of newborns weighing less than 15-hundred grams rose from 0.2 percent to 0.4 percent over the seven-year period.

According to the study, the percentage of babies born prematurely also went up to four-point-nine percent in 2006 from three-point-eight percent seven years earlier.

Births by women aged 35 or older accounted for about 12 percent of all newborns in 2006, about twice the percentage from seven years ago.

Doctor Kim attributed the increase in underweight babies to smoking during pregnancy, late marriages, and improper diets. She also said increased cases of multiple gestation added to the higher percentages of underweight infants.