The Ministry of Health is warning pregnant women who take a common anti-depressant to consult their doctors after the medicine was linked to an increased risk of heart defects at birth.
Two overseas studies have linked paroxetine to cardiac abnormalities in babies. Paroxetine is this country's most popular antidepressant, taken by more than 54,000 people. It is sold under the Paroxetine and Aropax brands.
The risk of any baby being born with a congenital heart defect is 1 per cent. The main defect is hole in the heart, a condition which sometimes will reverse after birth.
Preliminary results from the studies showed the heart-defect risk rose to 2 per cent in the babies of women who took paroxetine during the first three months of pregnancy - an increase the ministry termed "small". Other drugs in the same class of antidepressants, called selective serotonin re-uptake inhibitors, were also associated with an increased risk, although this was less than for Aropax.
Ministry medicine regulation spokesman Stewart Jessamine said the results contradicted earlier research and it was unclear if paroxetine caused the apparent increased risk.
Women taking paroxetine who were pregnant or planning pregnancy should see their doctor to discuss whether they should continue using it, gradually stop, or change to another anti-depressant.
Most patients responded to most antidepressants, he said, but some responded only to one, so it was important that paroxetine continued to be available for pregnant women who were helped only by it.
Up to a tenth of the more than 50,000 women who give birth in New Zealand each year suffer mild to severe depression during pregnancy.
Dr Catherine Hapgood, a psychiatrist at the Waitemata District Health Board's maternal mental health service, said there was reluctance to prescribe any antidepressants during pregnancy, "but there are a group who need them". A pregnant woman's severe depression - including not eating or drinking - could affect a foetus, she said, adding that "suicide is one of the leading causes of maternal death ... [although] it's rare".