The participants involved in the Auckland Birthweight Collaborative Study were born between October 1995 and November 1997, but only the 871 participants of European descent were followed up after the age of 3 because of a low response rate from other ethnic groups.
As part of the study, parents were asked whether they had taken paracetamol, aspirin, antacids and anti-inflammatories during pregnancy. There were only significant links to behavioural difficulties with those who had taken paracetamol - which was taken by almost half of the women surveyed.
When their children were 7 years old, the most common behavioural problems were emotional and conduct-related. When their children were 11 years old, the problems were mostly related to hyperactivity and inattention.
Lead researcher Dr John Thompson said the results were alarming and indicated more research needed to be done to assess the exact risk and consequences of taking paracetamol during pregnancy.
"Paracetamol is the first thing we go for because everybody thinks it is nice and safe."
However, he said the thing about paracetamol was it crossed the placenta so could affect the fetus.
Professor Wayne Gillett, head of department of women's and children's health at the Dunedin School of Medicine, said stopping paracetamol use was not the right approach as the risk was small and the findings were based on limited studies.
"As a general rule paracetamol is still a very safe treatment ... If it wasn't available then gosh, only more dangerous drugs would be used or none at all which of course would lead to misery in women." Any medicine should be used cautiously and in balance, he said.
The study
• Data analysed from Auckland Birthweight Collaborative Study, which began in 1995.
• Mothers were asked whether they took paracetamol, aspirin, antacids and anti-inflammatories during pregnancy.
• Parents were surveyed when their children were 7 years old and both children and • parents were surveyed when the children turned 11.
• A link was found between children whose mothers had taken paracetamol during pregnancy and ADHD-like behaviour.
What is ADHD?
• Stands for attention deficit hyperactivity.
• The most common neurodevelopmental disorder among New Zealand school-age children.
• Main characteristics are inattention, hyperactivity and impulsiveness.
• Affects 5-10 per cent of children.
After effects worry for mother
Hamilton mother-of-two Hayley Nak took paracetamol during both her pregnancies and is now shocked to learn it may affect her children later on.
Hayley Nak with 5 month old Cecelia.
When the 29-year-old was pregnant with her first daughter Larissa, now almost 3, she caught chicken pox and was prescribed paracetamol. Her doctor ruled against anything stronger.
When pregnant with Cecelia, now 6 months old, she battled sinus infections and was again given paracetamol and other medication.
At no stage when she was being prescribed paracetamol did her doctor raise any potential risks and it was not until after she had her daughter that she learned about reports linking it to ADHD. She also spoke to her midwife about taking paracetamol at the time and she did not raise any concerns.
"They are both getting their regular Plunket visits and are at the doctors and everything is fine so I'm just hoping that is not going to be the case."
