About 5 million babies all over the world are born and conceived through assisted reproductive technology, experts said.

In the United States, the rate of children conceived through in-vitro fertilization (IVF) treatments is high. According to the Society for Assisted Reproductive Technology (SART), more than 63,000 babies were born through the reproductive technique in 2013.

With that number, families and medical experts are concerned about the long-term side effects of the treatment in "test-tube" children.

Because most couples that go through the IVF treatment are older, there is a range of health factors that could potentially affect fetal growth and development.

"Patients with infertility are often older, and may have medical conditions. You have to be able to differentiate those potential effects from any effects of the fertility treatment, per se," said Dr. Norbert Gleicher of the Center for Human Reproduction.

Is There A Possible Link Between IVF And Neurological Disorders In Children?

Past studies have suggested that IVF is significantly associated with several negative outcomes: congenital birth defects, low birth weight, minor problems in brain development, and premature birth.

Researchers from the University of California, Los Angeles (UCLA) found that among 4,795 babies conceived through IVF in California, 3,463 IVF babies were born with birth defects.

They also compared IVF babies and other babies conceived through other ART techniques with those who were naturally conceived. About 9 percent of IVF children had birth defects compared with 6.6 percent of non-IVF children. This led them to conclude that babies conceived through IVF were 1.25 times more likely to be born with abnormalities.

The catch is, the risk for birth defects was only found to be higher in IVF children than in children born through artificial insemination or ovulation induction.

UCLA researchers said the birth defects are possibly the result of whatever was contributing to infertility in the first place, but the difference between IVF babies and other ART babies somehow show that the procedure done in IVF is the primary culprit, they said.

Meanwhile, in a 2013 study conducted in Swedish children, scientists from the King's College also conducted the same research. They found that 47 children in 100,000 IVF babies had developed cognitive deficiencies.

Lead author Sven Sandin said mental retardation may potentially be added to the list of effects of IVF.

However, researchers said that factors linked to poor fertility may be at play in their findings, and that the development issues in the study were not debilitating and were minor abnormalities.

"Suboptimal neurological condition does not imply overt problems in daily life. It does, however, indicate an increased vulnerability for developmental problems such as learning and behavior problems," the authors wrote. "This means that our findings do not have significance on the level of the individual child, but that they do have significance for the population at large."

Still, no matter what the results are, experts say there is no way to easily reach a conclusion regarding the matter.

However, a new study in New York offers reassurance for couples who rely on assisted reproductive techniques.

Fear Not, There Is No Difference In Development Delays

A team of researchers from the National Institutes of Health, the New York State Health Department and other institutions found that delays in growth and development are not prevalent in children conceived through IVF.

Test-tube children are also not at a greater risk for developing learning disabilities, autism, or speech and language disorders compared with children conceived naturally, they said.

In a study featured in the journal JAMA Pediatrics, the team evaluated year 2008 to 2010 data from 4,824 mothers of 5,841 children in the state of New York, excluding New York City. Of the children, 1,830 were conceived through IVF treatment, and 2,074 were twins.

To see if there were any delays in growth and development, researchers collected data about the children at four, eight, 12, 18, 24, 30, and 36 months.

In the end, the team found that there were no differences between children who were born through IVF and children who weren't. About 13 percent of IVF children had delays, while 18 percent of non-IVF children had delays.

"This is a feel-good message of really just reassuring couples who are considering infertility treatment," said Dr. Edwina H. Yeung, the study's lead author.

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