THE latest celebrity craze for tracking the progress of unborn children via home ultrasound may not be such a good idea after all.
While there is little evidence that routine scans are harmful to a developing fetus, a study of mouse pups suggests that further research into antenatal ultrasound, particularly unnecessary non-medical scans, might be warranted.
The pups showed some evidence of disrupted brain development, although the team does not yet know if their mental function is impaired.
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Pasko Rakic of Yale University medical school and his colleagues injected mouse embryos with a chemical that would allow them to trace the migration of brain cells after birth and then exposed the embryos to ultrasound during the third week of gestation, a crucial period in which mouse brain cells become organised. In humans the main period of neuronal migration is between 11 and 15 weeks.
Dissections following the birth of the mice showed that a small percentage of brain cells had not moved to their normal place. For example, in mice exposed to two 30-minute ultrasound sessions, 6 per cent of the chemically tagged brain cells had not migrated normally (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0605294103).
It may be that the ultrasound waves somehow disrupt the connections formed between cells as they move into their proper location, says Rakic. His team has not yet tested to see if the mice have abnormal mental abilities.
And unlike scans on pregnant women in which medical staff continuously move the ultrasound transducer, the mice were exposed to a constant source of ultrasound waves, which could have increased the risk of disrupting the migration of brain cells. The distance between the embryos鈥� brains and the ultrasound transducer was also shorter than when a woman is scanned.
Pregnant women should not interpret the study as a reason to skip a scheduled scan. 鈥淚t would not be reasonable to extrapolate findings in the mouse model to appropriately performed obstetric ultrasound in the clinical setting,鈥� says Frank Chervenak at the Weill Medical College of Cornell University, New York. 鈥淭he widespread utilisation of obstetric ultrasound during the past generation has transformed pregnancy from the dark ages to an era of enlightenment,鈥� he says. Pregnant women typically have two scans 鈥� one at 12 weeks and another around 18 weeks.
鈥淚t would not be reasonable to extrapolate the mouse findings to appropriately performed obstetric ultrasound鈥�
The US Food and Drug Administration recently advised women not to have commercial ultrasound movies made of their unborn babies, while states such as California have tried imposing stricter regulations on non-medical scans, such as those offered to expectant mothers in US shopping malls for $200.
