Pregnant women can be reassured there is no evidence repeated ultrasounds will harm their baby, scientists say.
Women can be reassured ultrasounds are safe, say experts
Ultrasounds have been carried out to check the health and development of foetuses for around 30 years.
But concerns had been raised that repeated scans could be linked to growth restrictions in babies.
However, a study by a researchers at the University of Western Australia published in the Lancet, found no evidence of long-term harm.
In the UK, it is recommended that women have two ultrasound scans - where images are created from sound waves - during their pregnancies.
In cases where there are concerns over the babies development, women may undergo more.
The Australian researchers had carried out a study in 1993 which suggested there could be a link between repeated ultrasound scans in late pregnancy (after 18 weeks) and growth restrictions among newborn babies.
In this latest study, they looked at the children's development up until the age of eight.
Physical and developmental checks were carried out on 2,700 children at the ages of one, two, three, five and eight.
Half had been exposed to up to five ultrasound scans while in the womb, while the rest had had only one ultrasound exposure before birth.
It was found that the physical sizes of the children were similar in both groups from the age of one upwards.
There were also no significant differences between the groups in relation to their speech, language, behaviour or neurological development.
Dr John Newnham, who led the research, said: "Exposure to multiple prenatal ultrasound examinations from 18 weeks' gestation onwards might be associated with a small effect on foetal growth.
"But is followed in childhood by growth and measures of developmental outcome similar to those in children who had received a single prenatal scan."
The researchers said uncertainty remained about suggestions repeated ultrasound exposure was linked to an increase in the number of left-handed babies born, but said the connection could be "nothing more than chance".
'Scanner must be trained'
Sanjay Vyas, a consultant in obstetrics and gynaecology at Southmead Hospital, Bristol welcomed the Australian research.
He said: "It is very reassuring to those of who use ultrasound and, just as importantly, to pregnant women.
"There are three things pregnant women worry about when they are undergoing any kind of procedure; what will the results be, what can't be seen and will having this test harm my baby.
"Some women also ask if ultrasounds are like an X-ray, which they associate with possible harm."
But Mr Vyas said women should check the person carrying out the ultrasound was trained, so they could be confident any problems would be detected and that something innocuous would not be misinterpreted.