Two new US studies suggest that taking SSRIs during pregnancy does not significantly increase the risk of most birth defects. However, both studies found that taking certain SSRIs while pregnant was linked with a small increased risk of some rare birth defects.
SSRI stands for selective serotonin reuptake inhibitor, a class of drugs used to treat depression, anxiety and some personality disorders.
The two studies are published today in the New England Journal of Medicine (NEJM).
One study was led by researchers at Boston University’s Slone Epidemiology Center. The other study was led by researchers at the University of British Columbia and the National Center on Birth Defects and Developmental Disabilities.
Dr Michael Katz, Acting Medical Director of the March of Dimes, a not for profit organization that aims to improve the health of babies by preventing birth defects, premature birth, and infant mortality, said that the two studies highlight the importance of continuing to monitor a drug’s safety after it has been approved and is being used by the population at large.
Clinical trials conducted on drugs in the run up to approval are tested on relatively few people which means that only the more common side effects are likely to emerge. Once a drug is approved, and much larger numbers of people start taking it, that is when the rarer side effects are noticeable.
Also, as Dr Katz pointed out, pregnant women rarely participate in clinical trials:
“Most prescription drugs are not tested on pregnant women,” said Dr Katz.
“So we must start monitoring the effects of these medications as soon as they reach consumers, and keep monitoring for as long as it takes to get good data on risks to mothers and babies,” he added.
In the study led by Boston university, researchers assessed the link between first-trimester use of SSRIs by pregnant women and the risk of birth defects among nearly 10,000 babies with defects and nearly 6,000 without. The patients were taking part in the Slone Epidemiology Center Birth Defects Study.
They found that overall use of SSRIs was not linked significantly to increased risk of craniosynostosis, omphalocele or heart defects. However, when they analysed individual SSRIs they found a significant link between the SSRI sertraline and two defects: omphalocele and septal defects.
Sertraline has several brand names for example Zoloft, Sertralin, Asentra, Gladem, Stimuloton, Xydep, Serlain, Serlift, and Concorz.
Craniosynostosis, also known as cloverleaf skull or kleeblattschadel, is a birth condition where the sutures in the skull of the newborn close too early, causing problems with brain and skull growth and creating pressure inside the skull.
Omphalocele is where the intestines, liver, and sometimes other organs protrude through the navel in a sac because the muscles of the abdominal wall don’t develop properly. This is a normal feature of the early fetus, but the protrusion comes back inside the abdomen in later development.
A septal defect is a fault in a part of the heart that separates the right atrium from the left ventricle.
The researchers pointed out that while their findings suggested some increased risks between individual SSRIs and certain defects, this was not the case with SSRI use overall and the the specific defects found are rare and the absolute risks are very small.
In the study led by the University of British Columbia and the National Center on Birth Defects and Developmental Disabilities, researchers used data from the National Birth Defects Prevention Study on nearly 10,000 babies with major birth defects and just over 4,000 without who were born between 1997 and 2002.
Information on exposure to SSRIs was obtained through telephone interviews with mothers and was defined as taking any SSRI from 1 month before to 3 months after conception. There were 26 categories and subcategories of birth defects.
As with the first study, the researchers found that the overall picture did not show significant links between SSRI use in early pregnancy and congenital heart defects or most other categories or subcategories of birth defects.
However, they did find a significant link between SSRI use and anencephaly, craniosynostosis and omphalocele. The researchers pointed out that the absolute risks were small and that their observations should be confirmed by other studies.
Anencephaly is a rare birth defect where a large part of the brain, skull and scalp is missing. It results from a defect in the development of the neural tube in the fourth week of pregnancy.
The March of Dimes does not advise women to stop taking their anti-depressant medication if they discover they are pregnant. They should talk to their doctor about the risks of the medication to themselves and their baby, and the doctor may recommend a change in prescription. It could be dangerous to stop taking anti-depressant medication abruptly.
Approximately one in ten pregnant women in the US suffer from depression, some of them undiagnosed.
“First-Trimester Use of Selective Serotonin-Reuptake Inhibitors and the Risk of Birth Defects.”
Louik, Carol; Lin, Angela E; Werler, Martha M; Hernandez-Diaz, Sonia; and Mitchell, Allen A.
N Engl J Med 2007 356: 2675-2683.
Volume 356:2675-2683; June 28, 2007; Number 26.
“Use of Selective Serotonin-Reuptake Inhibitors in Pregnancy and the Risk of Birth Defects.”
Alwan, Sura; Reefhuis, Jennita; Rasmussen, Sonja A; Olney, Richard S; Friedman, Jan M; the National Birth Defects Prevention Study.
N Engl J Med 2007 356: 2684-2692.
Volume 356:2684-2692; June 28, 2007; Number 26.
Written by: Catharine Paddock
Writer: Medical News Today