The study says the rate of cases of the rare condition is double in infants born to women who take selective serotonin-reuptake inhibitors in late pregnancy.
Because of the way the study is designed, the authors cannot say the drugs cause the condition; they can only note there is an association between the use and increased cases of the condition.
They saw the suggestion of increased risk in several different types of SSRIs, suggesting the risk relates to the class of drugs, not one individual brand.
A commentary on the findings by researchers from the Hospital for Sick Children's Motherisk program points to holes in the study, saying other issues might account for the findings.
Motherisk director Dr. Gideon Koren and a colleague wrote that while the findings suggest a possible causative link, more work is needed.
The study, by researchers from the Karolinska Institute in Stockholm, Sweden, is being published in the medical journal BMJ.
Persistent pulmonary hypertension — high blood pressure in the lungs — can be life-threatening, and is seen in about one or two out of every 1,000 newborns. Babies born to women who are overweight, who smoke, who have diabetes or use non-steroidal anti-inflammatory drugs in pregnancy are known to be at increased risk.
Several previous studies have looked at whether SSRI use in pregnancy increases the risk that the resulting baby will be born with persistent pulmonary hypertension.
But the findings have been inconclusive. They have ranged from no association to the suggestion that women who used the antidepressants were six times more likely to give birth to a baby who develops the condition.
The new study looked at records for 1.6 million full-term births in the Denmark, Finland, Iceland, Norway and Sweden between 1997 and 2006.
Of those, about 30,000 were babies born to women who had prescriptions for SSRIs in pregnancy, and roughly 11,000 had prescriptions in late pregnancy. That is where the increased rate of the condition was seen. The authors used 140 days into the pregnancy onward for their definition of late.
They recommended doctors use caution when treating pregnant women with SSRI antidepressants. "It is essential to plan the treatment and to weigh the risks of persistent pulmonary hypertension of the newborn when treating women in late pregnancy with those of relapse of depression and neonatal abstinence syndrome if therapy is interrupted," they said.
But Koren's commentary noted that filling a prescription for a drug doesn't mean the women took it, and pointed out a recent study showed that many women with depression did not take their antidepressants during pregnancy.