Women who take antidepressants while pregnant may face a slightly increased risk of developing high blood pressure, a potentially serious complication, according to a new study.
It could be an important finding because antidepressants are among the most commonly used drugs during pregnancy. And the solution isn't as simple as going off the medication because that could lead to worsening symptoms of depression.
In a study published in the British Journal of Clinical Pharmacology last week, Canadian researchers looked at data from more than 1,200 pregnant women in Quebec who developed high blood pressure during pregnancy and compared them to more than 12,000 pregnant women without high blood pressure.
They determined that women taking selective serotonin re-uptake inhibitors, a class of antidepressants that includes brand-name drugs such as Prozac and Zoloft, were more likely to develop high blood pressure.
Specifically, researchers found that about 3.5 per cent of women with high blood pressure were taking antidepressants, compared to just 2 per cent in the control group, which is a 53 per cent increase.
But the researchers caution that the actual increase in risk is very slight and that pregnant women taking antidepressants shouldn't go off the drugs without talking to their health-care provider.
Although the findings don't establish a cause-and-effect relationship – it's impossible to say whether the medication caused the high blood pressure – they do raise important concerns about the need for better understanding of drugs and pregnancy, said the lead author Anick Bérard, director of the research unit on medications and pregnancy at CHU Sainte-Justine Research Centre in Montreal.
"We're far from knowing everything that we would like to know with regards to antidepressant use during pregnancy," said Dr. Bérard, who is also a professor in the faculty of pharmacy at the University of Montreal.
High blood pressure during pregnancy can lead to complications, cause damage to the mother's kidneys and other organs and lead to low birth weight or early delivery.
It can also cause a potentially deadly condition called pre-eclampsia, characterized by high blood pressure and excess protein in the urine after 20 weeks gestation. Although many women with pre-eclampsia have healthy babies, serious complications can occur, such as lack of blood flow to the placenta, separation of the placenta from the wall of the uterus, seizures in the mother and permanent organ damage.
"I think any risk is a concern during pregnancy," said Dr. Bérard. "There's no small risk."
This isn't the first time warnings have been sounded about the impact of antidepressants in pregnancy.
Health Canada issued a warning in 2006 after a study published in the New England Journal of Medicine found taking SSRI antidepressants in the second half of pregnancy was linked to persistent pulmonary hypertension in the newborn. It's a rare condition but potentially fatal that occurs when newborns don't receive enough oxygen in the blood.
A study published earlier this year in the British Medical Journal confirmed mothers who take SSRIs are more likely to have newborns with persistent pulmonary hypertension.
Health Canada also notes that SSRIs and other newer antidepressants have been linked to other complications as well as an increased risk of birth defects.
Dr. Bérard said part of the problem is that not enough research has been dedicated to looking at the effects of antidepressants and other types of medication in pregnant women.
"Medications are never tested in pregnant women before they come on the market," she said. "When a drug is marketed, we have zero clinical data on how it's going to behave in pregnant women."
The issue of antidepressants during pregnancy is tricky. Women who don't take medication for symptoms of depression could experience worsening symptoms, making it difficult to take care of themselves or their baby.
The Therapeutics Initiative, a Vancouver-based organization that provides information about drug safety, points out that while some research has suggested depressed pregnant women are more likely to have problems such as premature deliveries, babies with a low birth weight or babies who need intensive care, there is no evidence that depression causes those outcomes.
Although many women are urged to take medication to deal with the symptoms of depression during pregnancy, the Therapeutics Initiative says that, based on the possibility of health risks and little evidence antidepressants lead to major improvements, the risks of medication outweigh the benefits for pregnant women.