Antidepressants decreased birthweights

June 27, 2016 - 06:20

The infants born to mothers who have used antidepressants during their pregnancy are more likely to be born prematurely and weigh less. That said, researchers are not advising women who use such medications to quit them when they get pregnant.

Annually, about 600 women in Norway use selective serotonin reuptake inhibitors (SSRIs), antidepressants, during their pregnancies. (Photo: Maria Hedegaard, Scanpix Denmark, NTB Scanpix)

Babies who have been prenatally subjected to antidepressants are born about 200 grams lighter than others on average.

These babies are also born on average five days earlier than other infants.

Researchers from Norway and Canada have discovered this through data from the Norwegian Mother and Child Cohort Study (MoBa) and the Medical Birth Registry of Norway (MBRN).

Most common antidepressant

The study looked at women using selective serotonin reuptake inhibitors (SSRIs).

This is currently the most common type of antidepressant used to treat depression.

In Norway around 600 pregnant women per year are known to be using SSRIs.

“For a child weighing four kilos at birth, a reduction of 200 grams doesn’t matter much. But if the baby is born prematurely even a small birthweight reduction can have an impact,” says Hedvig Egeland Nordeng, a professor at the University of Oslo’s School of Pharmacy.

Nothing known about the cause

The study has been published in the International Journal of Epidemiology.

Author Katerina Nezvalova-Henriksen says in a press release that the biological mechanism involved here is still a mystery.

The medical researchers do not know whether it’s the medicine or something else which is causing the lower birthweights and premature deliveries. 

“We cannot rule out that the degree of severity of the mother’s depression is a cause of these differences, rather than the use of the medication,” says Nordeng.

Could cause more anxiety amongst the offspring

Research last year showed that the three-year-old children of mothers who had used antidepressants during their pregnancies had more anxiety symptoms than their siblings who had not been prenatally exposed to the medication.

A large study from the University of Montréal in 2015 has shown that the risk of having children with autism increases by 87 percent if women take SSRIs in the second and third trimesters of their pregnancies. Here too, it is uncertain whether the increased risk can be attributed to the medication or the depression.

Restrictive practice

The study has not triggered a change in guidelines for the treatment of pregnant women who suffer from depression. Medical guidelines call for this mental illness to be treated with medications because depression can have strong negative consequences for the mother and the child.

The first choice for mild or moderate depressions is treatment without the use of drugs, for instance conversational therapy, family therapy or cognitive therapy. When these fail to have a sufficient effect, antidepressants might have to be prescribed as well.

“My impression is that doctors who prescribe antidepressants to pregnant women in Norway have conducted thorough evaluations of the pros and cons of the medication. In general, Norwegian physicians are restrictive regarding medications to pregnant women. The women they prescribe them to really need the medications,” says Nordeng.

She says that some women discontinue use of the medications during pregnancies to avoid harming the foetus. In some cases, they start self-medicating with alcohol or other intoxicants instead. This is much more harmful for the unborn baby.

“The pregnant woman should always discuss the issue with her MD first if she is considering cutting out her use of a prescribed antidepressant.”

Sibling comparisons

Nordeng calls for more research on the use of antidepressants during pregnancy to get a better understanding of the findings.

Over 100,000 mothers and children have been included in the studies of the MoBa and MBRN registers.

The researchers studied siblings in the cohort study. This has enabled them to compare siblings who were exposed to SSRIs in the womb with their brothers or sisters who were not. This research design enabled them to take genetic sibling factors into account that could have impacted birthweights and gestational age. 

The study concludes that genetic sibling factors cannot explain the links found by the researchers.

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Read the Norwegian version of this article at forskning.no

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Translated by
Glenn Ostling

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