Researchers have found an increasing number of pregnant women are using the drug methamphetamine, or P, leading to mental illness and poor mother-child relationships.
Auckland University lecturer in psychological medicine Trecia Wouldes runs a unit studying the use of methamphetamine by pregnant women.
The unit is one of five involved in the research, along with four in the United States.
Dr Wouldes says the number of P-addicted pregnant women referred to her unit was more than double of any of the others.
She says there's a close correlation between the use of the drug and mental illness in the women, which will ultimately affect their child's development.
Dr Wouldes says the children are likely to have learning difficulties, and may be bullies, or bullied themselves, at school.
