Pregnant women who take common, over-the-counter pain relief tablets containing paracetamol could cause their newborn children to develop serious behavioural problems, a study found.
A survey of Danish mothers shows that taking the drug during pregnancy increased the risk of a child developing a severe form of attention deficit and hyperactivity disorder (ADHD).
The Department of Health in Hong Kong said while the study had raised possible concerns on the use of paracetamol in pregnancy, more studies were needed before any conclusions could be drawn on whether the clinical guideline for using such drugs should be amended.
The Hospital Authority, which runs local public hospitals, said clinics would continue to prescribe paracetamol, which is also known as acetaminophen, according to the condition of patients. The leading painkiller brands in Hong Kong containing paracetamol are Panadol and Coltalin.
The study, published on Monday in the Journal of the American Medical Association Pediatrics, came to its conclusions based on survey data on more than 64,000 Danish women from 1996 to 2002.
More than half said they took paracetamol at least once during pregnancy.
Women who took the drug while pregnant had a 37 per cent higher risk of having a child who would later be given a hospital diagnosis of hyperkinetic disorder - the particularly severe form of ADHD.
They also had a 29 per cent higher chance of having children who were later prescribed medication for attention deficit hyperactivity disorder, and a 13 per cent higher chance of exhibiting ADHD-like behaviour by age seven.
"Findings from this study should be interpreted cautiously and should not change practice," said an accompanying editorial in the journal by Miriam Cooper and colleagues at the Cardiff University School of Medicine.
"However, they underline the importance of not taking a drug's safety during pregnancy for granted."
The president of the Society of Hospital Pharmacists of Hong Kong, William Chui Chun-ming, called the finding "shocking" as paracetamol had always been considered safe for pregnant women.
"This is the one medicine that pregnant women have relied on when they suffered pain or fever."
But he believed it was not yet necessary to stop using paracetamol at this stage.
Drugmaker GlaxoSmithKline, which produces Panadol, did not reply to questions from the Post.