Preterm babies have double the risk to be born with major birth defects than full-term infants, a study by the U.S. Centers for Disease Control and Prevention’s National Center on Birth Defects and Developmental Disabilities, the March of Dimes Foundation and several other organizations revealed.

Lead author Margaret Honein, PhD, MPH of the CDC and colleagues analyzed 6.9 million babies born between 1995 and 2000 in 13 states, accounting for about 30 percent of U.S. births in order to better understand the relationship between birth defects and preterm birth.

In fact, the study comes at a time when preterm births hit record numbers nationwide. More than a half million babies are born too soon each year and the rate continues to rise. That prompted federal officials to authorize more research and education into the causes and effects of premature birth.

“The causes of most birth defects are still not known. While it is likely that the most common defects are caused by a combination of genetic and environmental factors, the identification of specific risk factors continues to be a major research and public health priority,” Honein said, according to Science Daily.

The study found that about 8 percent of preterm babies, those born before week 37 of pregnancy, had a birth defect, but things looked even worse for very preterm babies, those born between 24 and 31 weeks gestation. They were five times as likely as full-term infants to have a birth defect.

Infants in this group usually had central nervous system defects, such as spina bifida, and cardiovascular defects, such as a hole in the heart.

Although causes of these birth defects are not sure, Honein blamed smoking during pregnancy and maternal obesity before pregnancy.

This study is not the first to highlight the dramatic consequences preterm births have on infants. No later than November last year, a study by the March of Dimes Foundation published in the Journal of Pediatrics found that preterm babies are more likely to die during their first week of life than full-term babies.

“We have known from previous studies that late preterm infants have greater risk of certain problems like respiratory distress syndrome (RDS), feeding difficulties, temperature instability (hypothermia), jaundice and brain development, Now we have evidence that there is a greater risk of death among these babies,” said Dr. Jennifer L. Howse, president of the March of Dimes Foundation at the time.

The new findings were published in this week’s issue of the Maternal and Child Health Journal.