Taking so-called selective serotonin reuptake inhibitors (SSRIs) — such as Prozac — after the 20th week of pregnancy more than doubled the risk, the study found.
SSRIs are a class of compounds typically used to treat depression, anxiety disorders, and some personality disorders.
The study, led by Helle Kieler at the Karolinska Institute’s Centre for Pharmacoepidemiology in Stockholm, looked at 1.6 million single births between 1996 and 2007 in Denmark, Finland, Iceland, Norway and Sweden.
In the general population, the number of newborns with the condition is 1.2 in 1,000, with a mortality rate among babies with high blood pressure in the lungs of 15 percent.
Newborns of some 17,000 mothers who filled out prescriptions for SSRIs before the eighth week of pregnancy showed a slight increased risk of having the condition.
But for 11,000 expectant mothers who took the drugs after week 20 of their pregnancies, the risk more than doubled.
Even for this group, however, the absolute risk for newborns remained fairly low: about three in 1,000, or a 0.2 percent, the researchers said.
Kieler nonetheless suggested that doctors who treat depression in pregnant patients consider a non-drug approach to the condition.
“As the risk in association with treatment in late pregnancy seems to be more than doubled, we recommend caution when treating pregnant women with SSRIs,” the researchers concluded.
The drugs analysed included fluoxetine, citalopram, paroxetine, sertraline, fluvoxamine and escitalopram. Fluoxetine is better known under the brand name
The study was published on Friday in the British Medical Journal.