Ultrasound scans and brain changes. (Pregnancy & Birth).

Swedish scientists have found evidence that ultrasound scans may cause brain changes in unborn babies. Their research is based on findings of men who were more likely to be left-handed that had mothers who received ultrasounds.

They believe the scans may have affected some male babies' central nervous systems. Some experts believe that a change from right- to left-handedness is indicative of some kind of brain alterations.

Seven thousand men were studied whose mothers had scans in the 70s. These were compared with 172,000 men whose mothers had not had scans. The study shows that ultrasounds may have produced an extra three left-handed babies per 100 births.

The biggest difference was found in the group born after 1975. This is when doctors introduced a second scan later in pregnancy. These men were 32 percent more likely to be left-handed than those in the control group. The researchers concluded there were some possibilities the ultrasound had affected the brain. Even though the risk may be remote, this was serious enough to merit concern.

The researchers stated, "The present results suggest a 30 percent increase in left-handedness among boys prenatally exposed to ultrasound.... If the association reflects brain alterations, this means as many as one in 50 male fetuses prenatally exposed to ultrasound are affected." The research showed no evidence of harm to the babies.

Researchers involved in the study are still encouraging women to have ultrasounds because the risk is not validated. The scientists state that the human brain undergoes critical development late into a woman's pregnancy. The male brain is especially vulnerable because it continues to develop later than the female brain. Women should be fully briefed on the risks of ultrasound and should avoid having scans unless they are essential.

--from http://news.bbc.co.uk/ and Epidemology, December 2001