Studies highlight risks of infertility treatments

(CNN) -- The first test-tube baby was born more than 20 years ago, but that doesn't mean the technology has been perfected in that time.

Two new studies released in this week's New England Journal of Medicine shows there are some serious risks using test tube technology -- risks that researchers say prospective parents need to know about.

The statistics are striking. So called test-tube babies -- born with the help of ART, or assisted reproductive technology -- are twice as likely to be born with a major birth defect compared to babies conceived naturally. Also, single birth babies born with this technology are twice as likely to weigh 5.5 pounds or less -- even if they're born full-term.

"I think the decision of whether to go with ART is a very personal choice and a very complex choice and I think all of the risks and benefits need to be weighed," says Dr. Laura Schieve of the Centers for Disease Control and Prevention.

But on a positive note, the studies show infertile couples who use treatments like in vitro fertilization still have a 90 percent chance of having healthy children.

The question remains. Why are test tube babies at higher risk for birth defects and low birth weight?

Researchers looked at aspects of infertility and found no explanation.

"That suggests to us that there may be something about the ART procedure itself that was related to this increased risk in low birth weight," says Schieve.

That's a concern for researchers who've seen an increase in the marketing of these infertility services. The use of these services increased almost 50 percent in recent years.

"We're concerned that couples may be exposing themselves to the risks of these procedures, these potential risks even though they may not meet the formal definitions of infertility," says Dr. Allen Mitchell of the Boston University School of Public Health.

That definition is failure to conceive after a year of trying on your own. For couples who don't fit the definition, the risks of infertility treatment may be too high.