Common drugs used to treat high blood pressure in pregnancy may affect a baby's development, although more research is needed, experts said today.
The medicines labetalol and methyldopa are sometimes given to women suffering high blood pressure, including mild to moderate cases.
Experts in the Netherlands examined 4,000 patient records from 12 hospitals for the study, which also involved following 202 children.
All the women had high blood pressure that developed in pregnancy or which had been made worse by being pregnant. High blood pressure in pregnancy affects about 7pc of women.
Their children were tested for central nervous system problems when between four and 10, including IQ, concentration, motor development and behaviour.
The results showed that around twice as many children exposed to labetalol had attention deficit hyperactivity disorder (ADHD) than those exposed to methyldopa.
They were also around four times more likely to have ADHD than children whose mothers had only been prescribed rest.
Meanwhile, youngsters exposed to methyldopa appeared to have more sleeping problems than those exposed to labetalol or whose mothers had been prescribed bed rest.
Test scores on other aspects of functional development did not differ between the groups.
The authors stressed they were working on a hypothesis and that more research would be needed to confirm a link between high blood pressure drugs and a baby's development.
The study was published in BJOG: An International Journal of Obstetrics and Gynaecology.
Its editor-in-chief Professor Philip Steer said: "Hypertensive diseases in pregnancy can lead to serious complications such as stroke if left untreated.
"For this reason, doctors prescribe antihypertensive medication to keep blood pressure down to reasonable levels."