Labetalol, a drug sometimes given to pregnant women with high blood pressure, has been shown to increase a child's chances of developing attention-deficit hyperactivity disorder (ADHD), according to preliminary tests in The Netherlands.
The drug was compared with the effect of another blood pressure drug, methyldopa, and found to be twice as likely to cause the disorder, although the scientists say more studies are needed to confirm this.
The research scrutinised the records of 4,000 women from 12 hospitals, which included testing 202 children. Each woman had high blood pressure, either been caused by their pregnancy or had been exacerbated by their pregnancy.
Scientists tested the IQ, concentration level, motor development and behaviour of the children when they were aged between four and 10. Around twice as many children whose mothers were given labetalol were found to have ADHD than those whose mothers were given methyldopa.
Compared with mothers who were given no drugs but told to rest instead, the labetalol children were four times more likely to have ADHD.
But the methyldopa children were found to have more problems with sleeping than labetalol children or those whose mothers were told to rest.
Other functional development did not differ between the children.
The scientists said they are still developing a hypothesis and confirming a link between the drugs and a baby's development would require further research.
The findings were published in BJOG: An International Journal of Obstetrics and Gynaecology.