A common antidepressant may increase newborn babies' risk of congenital and heart malformations, if it is prescribed in the first 12 weeks of pregnancy, experts warn.

Paroxetine, a selective serotonin reuptake inhibitor or SSRI, is used to treat depression, anxiety disorders, obsessive-compulsive disorder as well as post-traumatic stress disorder.

Around one in five women of childbearing age suffer depressive symptoms, that can lead to mild to moderate depression.

Scientists note prescriptions for antidepressants in pregnancy have increased in recent years.

A review of 23 studies into the effects of the antidepresant paroxetine, a selective serotonin reuptake inhibitor or SSRI, found babies exposed to the drug in the first 12 weeks of pregnancy are at 23 per cent higher risk of congenital malformations (file image posed by model)

The most common drugs used to treat depression in pregnant women are SSRIs.

And up until 2005, one drug in that class - paroxetine - was considered safe to use during pregnancy.

However, a small, unpublished study conducted by the manufacturer, suggested an increased risk of cardiac malformations in infants exposed to the drug before birth.

Meanwhile, subsequent pieces of research using various study designs in different populations across Europe and North America generated conflicting results.

However, a trend remained towards an increased risk.

To provide a comprehensive assessment of the effect paroxetine has on newborns, researchers led by Professor Anick Bérard of CHU Sainte-Justine and the University of Montreal, reviewed all relevant studies on the topic, published between 1966 to 2015.

They analysed a total of 23 eligible studies.

When compared with babies who had never been exposed to paroxetine, those exposed to the drug in the first trimester - 12 weeks - were found to have a 23 per cent increased risk of major congenital malformations.

Clinical decisions regarding whether or not to treat depression in pregnancy are made by balancing the potential risks of an untreated illness with the potential small risks of treatment Dr Michael Bloomfield, UCL

Furthermore those newborns were found to have a 28 per cent increased risk of major cardiac malformations.

The investigators noted the baseline risk of major malformations is three per cent, and of cardiac malformations is one per cent.

However, they said any increase is significant, especially when considered that the benefit of using SSRIs during pregnancy - a time when changes in metabolism cause the drugs to be cleared from the body at a faster rate - is debatable.

Dr. Bérard said: 'Given that the benefits of antidepressants overall, and selective serotonin reuptake inhibitors, including paroxetine specifically, during pregnancy is questionable at best, any increase in risk - small or large - is too high.

'Indeed, the risk/benefit ratio suggests non-use in women with mild to moderately depressive symptoms, which is 85 per cent of pregnant women with depressive symptoms.

'Therefore, planning of pregnancy is essential, and valid treatment options such as psychotherapy or exercise regimens are warranted in this special population.'

Despite the study's findings, experts urged caution, noting each case should be assessed carefully for its pros and cons by the pregnant woman and her doctor.

Dr Patrick O'Brien, of the Royal College of Obstetricians and Gynaecologists, who was not involved in the review, said while the 'absolute risk remains very low' there does exist 'a small increased risk of birth defects'.

Furthermore, those babies exposed to the common SSRI, used to treat depression, anxiety and OCD, were found to be at 28 per cent greater risk of cardiac defects. However, experts have urged caution, noting depression in pregnancy can be very serious for women, and can impact on the health of her baby, adding it is vital to consider the benefits of antidepressant medication on a case by case basis (file image)

'Depression in pregnancy can be very serious for women and can also impact on the health of her baby, so it's important to consider the benefits of antidepressant medication in such cases,' he said.

'Our advise for pregnant women suffering with depression would be that generally the benefits outweigh the risks.

'However, all pros and cons should be discussed and weighed up by a woman, together with her obstetrician.'

Dr Michael Bloomfield, clinical lecturer in Psychiatry at the MRC Clinical Sciences Centre and University College London, agreed.

He said: 'While depression during and following pregnancy is very common, it can be a potentially devastating and life-threatening illness, both to the mother and her infant.

'Clinical decisions regarding whether or not to treat depression in pregnancy are made by balancing the potential risks of an untreated illness with the potential small risks of treatment.

'Owing to existing concerns about safety of paroxetine in pregnancy it is not currently recommended as the first line treatment for depression.'

Dr Bloomfield said further, larger studies are needed 'on this important topic to tease out many potential confounding factors in this research relating to cause and effect'.