Children conceived with assisted reproductive technology have similar early childhood development as other children, after multiple births are taken into account, according to a new study.

"This is a feel good message of really just reassuring couples who are considering infertility treatment," said lead author Edwina H. Yeung of the Eunice Kennedy Shriver National Institute of Child Health and Human Development in Bethesda, Maryland.

There has been longstanding concern that infertility treatment may affect brain development in childhood, but in the new study, children born of these treatments were no worse off except that they were more often born as twins or multiple births than children conceived without fertility treatment, the authors wrote.

Since multiple births may affect childhood development and mothers have a higher risk of pregnancy and delivery complications, the results should further encourage fertility specialists to use techniques that decrease the risk of multiple births, like single embryo transfer, Yeung told Reuters Health by phone.

The researchers tracked more than 5,800 infants born between 2008 and 2010 in upstate New York, including 1,830 who were conceived with fertility treatments and 2,074 who were born as twins.

Infertility services or medications used by some mothers in the study included oral or injectable medicines that stimulate ovulation, or ovulation induction plus intrauterine insemination, or so-called assisted reproductive technology, such as in vitro fertilization, frozen embryo transfer or donor eggs or embryos.

Several times until the children reached age three, parents completed an Ages and Stages Questionnaire assessing their child's fine motor and gross motor skills, communication, personal-social functioning, and problem-solving ability.

Infertility treatment in general was not associated with children failing in any of these areas.

Assisted reproductive technology was associated with an increased risk of failing one or more of the domains, but the association went away when the researchers accounted for singletons and twins separately. It was reduced further when the researchers accounted for birth weight, which is usually lower for multiple births, according to the report in JAMA Pediatrics.

These results further support that the procedures used today are safe, said Sven Sandin, a statistician and epidemiologist at the Karolinska Institutet in Stockholm, Sweden, who was not part of the new study.

"Especially earlier, multiple embryos were transferred to increase the success rate," Sandin told Reuters Health by email. "Such a procedure will result in an increased rate of twin birth, and twins have a well-known increased risk of autism and many other outcomes."

"If there is an increased risk among twins but not among singletons one could suspect that the observed risk is associated with twinning and not with the procedures per se," he said.

Some diagnoses, like autism, usually don't happen by age three, so Yeung and her coauthors are following the same group of kids through age eight.

Infertility treatments are becoming more common, but still only 1 to 2 percent of births are conceived with assisted reproductive technology in the U.S., she said.

That makes it hard to study enough children to compare the risks and benefits of different types of fertility treatment, she said. This study included mostly Caucasians, so it may not be generalizable to other ethnicities, she said.

"The techniques should be fairly similar in other regions and health systems even though the underlying cause for choice of ART at all or a specific procedure may differ," Sandin said.