Ultrasound Might Affect Baby's Brain Development

Mouse study suggests a link, but experts say more research is needed

TUESDAY, Aug. 8, 2006 (HealthDay News) -- Preliminary findings in mice suggest that fetal ultrasound might affect newborn brain development.

In baby mice whose mothers were exposed to ultrasound for 30 minutes or longer during pregnancy, a small but significant number of nerve cells did not migrate to their proper locations in the brain, Yale University researchers reported in this week's Proceedings of the National Academy of Sciences.

"These results call for a further investigation in larger and slower-developing brains of non-human primates and comprehensive epidemiological studies in humans," the team wrote.

But Dr. Pasko Rakic, chairman of the Yale department of neurobiology and leader of the study, was quick to offer parents reassurance about the safety of ultrasound -- done for the proper reasons -- in human pregnancies.

"If I had a daughter and she was pregnant, I would recommend she had it for medical reasons," Rakic said.

"I couldn't agree with him more," said Dr. Joshua Copel, a professor of obstetrics, gynecology and reproductive sciences at Yale and spokesman for the American College of Obstetrics and Gynecology (ACOG). He was not involved in the study.

Copel stressed that, to minimize any risk, "ultrasound should be performed for medical reasons, not for entertainment."

The researchers noted that mice are very different from humans, so the results of their study must be interpreted with caution.

"The forms of migration [of brain cells] and the timing of migration differ in primates like humans than in mice," Copel said. "In humans, there is a much longer period in which neurons [nerve cells] are migrating."

"This was only done in the mouse," Rakic said. "We are going to do the same study in larger animals that are more similar to humans."

A study reported in 2004 by Australian researchers found that repeat ultrasound exams during pregnancy had no long-term effect on either the mental function or growth of children.

That study included more than 2,700 children whose mothers-to-be had ultrasound examinations. The children were examined at 2, 3, 5 and 8 years of age by researchers at the University of Western Australia. They reported no significant differences among the children that might indicate prenatal ultrasound exams had deleterious effects on development.

Nevertheless, Copel said, there is good reason to follow ACOG guidelines, which state that "the lowest possible ultrasound setting should be used to get the necessary diagnostic information" and that the examination should be as brief as possible. A typical pregnancy ultrasound tests lasts 15 to 20 minutes.

"Time and range should be kept to a minimum," Copel said.

While ACOG recommends that ultrasound examinations be done for specific reasons, such as a suspected ectopic pregnancy, a possible miscarriage or detection of possible birth defects, many physicians include one examination as part of routine care, at 18 to 20 weeks of pregnancy. The March of Dimes Birth Defects Foundation estimates that 70 percent of American women have at least one ultrasound examination during their pregnancy.

More information

For more on ultrasound in pregnancy, head to the March of Dimes.

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