Children whose mothers were treated with a medication used for high blood pressure in pregnancy may be more at risk of developing behavioural disorders, according to new research.

Researchers in the Netherlands examined a study of women who developed high blood pressure during pregnancies in the 1980s and discovered that those women who were treated with one particular medication were significantly more likely to have children with ADHD (attention-deficit hyperactivity disorder).

However, obstetricians and gynaecologists in the UK have described the study as ‘limited’ and say women should not be alarmed by the findings.

Pre-eclampsia

High blood pressure ( hypertension) affects between 10% and 15% of women in pregnancy. Women with the condition fall into three categories:

  * Pre-eclampsia: a serious condition which can lead to seizures and occasionally to death if left untreated (2%-5% of pregnancies)
  * Chronic hypertension: where women have already had high blood pressure before getting pregnant (1%-3% of pregnancies)
  * Gestational hypertension: where high blood pressure develops because of the strain put on the woman’s body by pregnancy (5%-10% of pregnancies)

Pregnant women with hypertension are treated with antihypertensive medication to reduce their risk of developing complications such as strokes and kidney damage.
Dutch hospitals

The Dutch researchers looked at a previous study of children born to mothers with pregnancy-induced hypertension (PIH) and pregnancy-aggravated hypertension (PAH) at 12 hospitals between 1983 and 1987. The women were treated with labetalol or methlydopa for PIH or PAH and were compared to women with PIH or PAH who were treated with bed rest - a popular non-pharmacological management at the time.

The same groups of women were approached when their children were between four and 10 years old for a follow-up study.  The children were assessed on their cognitive and behavioural development in areas such as concentration, memory, IQ and gross and fine motor development. 
‘Higher risk’

Out of a total of 4,000 cases, the researchers selected 202 for closer investigation. They found that the children who had been exposed to labetalol before birth had a ‘significantly higher risk’ of ADHD than those who had been prescribed bed rest. Also, some children exposed to methyldopa went on to develop sleeping problems.

They note that previous research has shown that babies of mothers given labetalol were more likely to be small for their gestational age, with possible consequences for brain development.

The findings appear in the latest edition of BJOG: An International Journal of Obstetrics and Gynaecology.
‘Plausible’

Professor Philip Steer, BJOG editor-in-chief, says in a news release: “The results of this study are interesting although they could have occurred by chance.  Nonetheless, there are plausible reasons why antihypertensive drugs may be harmful to the functional development of the foetus, with long-term effects.

“One always has to balance the short-term benefits of a treatment against possible long-term consequences.  The results suggest that more large-scale studies looking at the effects of antihypertensive drugs on the baby long-term are warranted.”

In a separate commentary on the paper, Professor Michael Belfort of the Department of Obstetrics and Gynecology at University of Utah Medical School in the US, questions the findings from the paper, suggesting that the collection of data might have been biased. He cites the low follow-up rate as one potential problem.

Belfort calls for better studies on the effect of medications given to pregnant women. “Until confirmatory data is available,” he says, “I do not believe that this study should prompt physicians to stop prescribing these drugs to hypertensive patients when they are indicated.

“Methyldopa and labetalol have for many years been primary agents used for control of blood pressure in pregnancy, and until such time as we have prospective trials that unequivocally show deleterious effects, we should be careful about avoiding them if they are indicated. Sometimes the avoidance of use of a drug because of a theoretical risk can lead to serious consequences as a result of under-treatment of a dangerous condition”.
‘Sceptical’

The Royal College of Obstetricians and Gynaecologists (RCOG) also expresses scepticism over the latest findings. It says the small number of children studied (202), along with other factors, limits the value of the research.

Dr Tahir Mahmood, RCOG Vice President, says in an emailed statement: “This study is interesting but it does not mean that pregnant women suffering from hypertension should be all prescribed with bed rest.  Indeed, there may be serious consequences for the woman if timely drug treatment isn’t provided. 

“At present, the benefits of using antihypertensive drugs, when indicated, far outweigh any theoretical risks associated with their use.”

He continued, “The RCOG advises all pregnant women to keep to their antenatal appointments with their midwives so that their pregnancy progress is monitored.  Further help will be provided and referrals to an obstetrician will be made if a woman’s pregnancy is considered high-risk.”

The RCOG says new guidelines are currently being drawn up for managing women with high blood pressure during pregnancy.

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By Peter Russell
WebMD Health News