Medical treatment must balance the health of the mother with potential adverse effects to the developing baby
Children born to women taking anti-depressants in early pregnancy have a small but important increased risk of heart defects, researchers say.
The study published in the British Medical Journal says depression affects up to 20% of pregnant women.
Exposure to anti-depressants in the womb caused problems in less than 1% of children.
The authors say the overall risk is very low and women should speak to doctors before stopping their drugs.
Selective serotonin re-uptake inhibitors (SSRIs) are medicines commonly used for the treatment of depression .
In 2005, the US Food and Drug Administration issued a warning about the SSRI paroxetine because of an increase in birth defects if it was taken during pregnancy.
Septal heart defects
This study looked at whether there was an association between SSRIs taken in the first trimester of pregnancy and malformations in over 400,000 children born in Denmark between 1996 and 2003.
Maternal age and smoking were taken into account.
The defects found are known as septal heart defects where there is a problem with the wall that divides the left side of the heart from the right side.
The researchers from Aarhus University in Denmark said these defects were 0.4% more prevalent in children of women who redeemed a prescription for an SSRI in the first trimester of pregnancy.
Two SSRIs, sertraline and citalopram, were associated with the problem.
Two others, paroxetine and fluoxetine, were not.
A four-fold increase in septal heart defects was found if women were taking more than one SSRI.
There were no other malformations associated with taking SSRIs.
The researchers say the absolute differences in heart defects were low.
Septal heart defects occurred in 2,315 (0.5%) of unexposed children, 12 (0.9%) of SSRI exposed children and 4 (2.1%) of children exposed to more than one type of SSRI.
They estimate that one child for every 246 children exposed was likely to suffer a heart defect.
Lars Henning Pedersen, who led the research, said: "Treatment of depression during pregnancy balances the risk of the medicine with that of the depression, and we investigated only a part of the information needed to make evidence based decisions.
"Even if SSRI use is causally related to septal heart defects, these heart defects might not necessarily require treatment and some might resolve spontaneously."
Professor Basky Thilaganathan, of the Royal College of Obstetrics and Gynaecology, said it was important to remember that many women who suffered depression could be treated without resorting to drugs.
He said: "All hospitals now have a dedicated doctor or liaison officer for women suffering psychiatric symptoms in pregnancy.
"This study shows a less than one in a 100 chance of getting a baby with a defect in the heart."
Cathy Ross, cardiac nurse at the British Heart Foundation (BHF), said: "Depression can be a debilitating condition.
"The benefits to the mother of taking SSRIs during pregnancy needs to be weighed up against the small increase in risk to the foetus."