And the effects, more pronounced in boys, can last until the end of primary school, British researchers claim.
Paracetamol is commonly used to relieve pain during pregnancy and is recommended as the treatment of choice by the NHS.
But scientists wanted to find out if there were any effects of taking paracetamol during mid-pregnancy and the behaviour of the child.
They said the results show an association between the drug and the effects they describe but the evidence is not strong enough to say the drug causes it.
Lead study author Professor Jean Golding of the University of Bristol said: “Our findings add to a series of results concerning evidence of the possible adverse effects of taking paracetamol during pregnancy such as issues with asthma or behaviour in the offspring.
“It reinforces the advice that women should be cautious when taking medication during pregnancy and to seek medical advice where necessary.”
The new study looked at children between the ages of six months and 11 years and tested their memory and IQ until the age of 17.
Researchers examined 14,000 children using questionnaire and school information from Bristol’s Children of the 90s study.
They also analysed the results of the children’s memory, IQ and pre-school development tests, temperament and behaviour measures.
When they were seven months pregnant, more than one in four mums said they had taken paracetamol sometimes or more often during the previous three months.
Scientists found a “casual link” between paracetamol intake and behaviour issues in children that were not related to the reasons why the medication was taken or to social factors.
But they added more research is needed to determine whether there is a firm association between the two and to understand whether such behaviour issues would be temporary or permanent.
Prof Golding added: “It is important that our findings are tested in other studies - we were not in a position to show a causal link, rather an association between two outcomes.
“It would also be useful now to assess whether older children and adults are free of difficult behavioural problems if their mother had taken paracetamol.”
The research was published today in the Paediatric and Perinatal Epidemiology medical journal.