Pregnant women who take certain anti-depressants can significantly increase their chance of having babies that develop a condition known as pulmonary hypertension, according to a study published Thursday in the British Medical Journal.
An estimated 1 in every 1000 babies born develop pulmonary hypertension, characterized by high blood pressure in the lung arteries, according to the American Academy of Pediatrics.
The condition occurs when newborn babies are not able to adapt to breathing on their own, which can potentially lead to organ failure and brain damage. On average, 11 percent of newborns diagnosed with this condition will die from it, according to the American Academy of Pediatrics.
The study suggests that women who took one of the most prescribed class of antidepressant medications known as selective serotonin reuptake inhibitors (SSRI) during pregnancy, were twice as like to have their baby develop pulmonary hypertension compared with mothers who didn't take SSRIs.
But many experts said the risk is still low.
"You're doubling the risk of extremely low risk to again, an extremely low risk," said Dr. Marjorie Greenfield, division director of obstetrics and gynecology at University Hospitals Case Medical Center in Cleveland.
SSRIs, more commonly known by their brand names such as Zoloft, Paxil, and Celexa and Lexapro, are taken by 1.5 percent of pregnant women in the U.S.
The study reviewed 6 million births that took place from 1996 to 2007 in Denmark, Finland, Iceland, Norway and Sweden.
Study researchers said they took into consideration the mothers' health conditions such as obesity, diabetes, or behaviors such as smoking, or the way the baby was delivered. These factors have previously been associated to a baby's development of pulmonary hypertension.
The U.S. Food and Drug Administration first issued a warning about the potential link in July 2006. The agency based their advisory on one study published in the New England Journal of Medicine that suggested pulmonary hypertension was six times more common in babies whose mothers took antidepressants after their second trimester compared with babies whose mothers did not take an antidepressant.
In December 2011, the agency revised its initial warnings, advising physicians to continue treating mothers with antidepressants.
"Given the conflicting results from different studies, it is premature to reach any conclusion about a possible link between SSRI use in pregnancy and PPHN [pulmonary hypertension]," according to the FDA safety announcement made in December.
Many physicians said that while it's unlikely the current study will change any larger guidelines, the large number of babies taken into account provides physicians with stronger evidence of a potential link.
"[These results] will add a layer of 'caution' in the continuation of treatment in late term pregnancy," said Dr. Amir Afkhami, assistant professor in the department of Psychiatry and Behavioral Sciences at George Washington University.
Previous studies also suggest that untreated depression during pregnancy can raise the risk of premature delivery and low birth weight.
"This risk is not small and therefore outweighs the risk of PPH [persistent pulmonary hypertension]," said Dr. Jennifer Payne, director of Women's Mood Disorders Center at Johns Hopkins School of Medicine.
A majority of women who stop medication during pregnancy relapse into depression, Payne said.
However, some women are able to function without medication during pregnancy, Greenfield said. And for them, finding alternatives such as talk therapy, or steering clear of medications could be helpful.
"There's risk to having unmedicated depression as well as risk for treating depression," said Greenfield. "There needs to be good communication with moms about weighing risks and benefits."