Using a standard dose of antidepressants during pregnancy appears to be safe for the baby, suggests new research from the University of Oslo and Akershus University Hospital. Persistently high doses, however, may be linked to changes in the placenta and a higher chance that the newborn needs intensive care.

Many women who become pregnant while taking antidepressants face a difficult decision: Should they continue their medication to protect themselves against severe depression, or stop to avoid possible risks to the baby?
“We know that untreated severe mental illness can be dangerous for both the baby and the mother,” says Professor Soili Marianne Lehto from the University of Oslo (UiO) and Akershus University Hospital (Ahus). “Lack of appropriate treatment can increase the risk of relapse, suicidal thoughts, poor engagement with antenatal care and complications in pregnancy. For many, this choice feels like an ethical and medical dilemma when it comes to antidepressant medications.”

Standard doses of antidepressants appear safe in pregnancy
In a new study, Lehto and colleagues examined the use of antidepressants during pregnancy and possible perinatal outcomes. The results indicate that using antidepressants at standard doses during pregnancy appear to be safe, based on the outcomes examined after birth.
“Using a standard dose does not seem to be harmful to the baby based on the factors we have assessed after birth,” says senior researcher Guro Pauck Bernhardsen at Akershus University Hospital.
The researchers looked at several perinatal outcomes, including birth weight, placental weight, umbilical cord length, preterm birth, as well as Apgar score (a rapid assessment of newborn health) and whether the newborn was admitted to the neonatal intensive care unit (NICU).

High, long-term doses linked to increased risk
The size of the dose is critical, according to the study. “We see that persistently high doses of antidepressants are associated with changes in the placenta. Sustained high doses are also linked to an increased risk that the baby will need treatment in a neonatal intensive care unit.” says Bernhardsen.

For women taking medication for severe mental illness and who are worried about continuing during pregnancy, these findings are partly reassuring. “Our findings support the view that use of standard-dose SSRIs during pregnancy may be safe. However, persistently high doses may carry extra risk. These women should be closely followed up by a doctor during pregnancy.”, says Bernhardsen.

The study: SSRIs, dose, duration and patterns of use
The researchers focused on one common group of antidepressants: SSRIs (selective serotonin reuptake inhibitors), widely used to treat depression and anxiety. “SSRIs are the most commonly used antidepressants in the Nordic countries, including among pregnant women,” explains Bernhardsen.
Unlike many earlier studies that categorized use simply as “yes” or “no,” this study examined dose, duration and usage patterns across pregnancy.

The team used registry data from Kuopio University Hospital in Finland. They compared 553 mothers who used antidepressants during pregnancy with 2,765 mothers who did not use antidepressants in pregnancy. The groups were matched on depression, other psychiatric diagnoses and age to make the comparison as similar as possible. Women who used antidepressants were divided into four categories based on how they took the medication: 1) Standard dose throughout pregnancy, 2) low dose that increased during pregnancy 3) high dose throughout pregnancy, and 4) tapering from a standard dose early in pregnancy down to a lower dose later. The researchers then examined outcomes for both mothers and babies after birth.

Why the placenta matters
For mothers who needed high doses of antidepressants throughout pregnancy, the researchers found several notable results. It is already known that placental weight correlates with infant birth weight; a relatively large placenta compared with the baby can indicate that the placenta has been less effective at supplying nutrients. In this study, women who took high doses had larger placentas and a higher placenta-to-birthweight ratio.

“Measuring placental size relative to the baby’s weight can provide important information about whether the baby achieved optimal growth in utero. Poor growth can indicate a need for extra follow-up after birth and may have implications for long-term health,” Bernhardsen explains.
These same infants had roughly double the risk of NICU admission compared with infants of women who did not use antidepressants during pregnancy.

Balancing medication changes against mental health risks
In Norway, just under 2% of pregnant women use SSRIs. “The lower proportion of SSRI use among pregnant women compared with non-pregnant women may indicate that many choose to stop treatment for depression during pregnancy. This is likely due to uncertainty about possible consequences for the foetus,” Lehto says.
She stresses the importance of individual evaluation of antidepressant dosaging in pregnant women. In addition, newborns of women on high doses should be observed more closely after birth. “The risks of changing or reducing treatment should always be taken into account when making decisions on antidepressant dosage in pregnant women,” Lehto emphasises.

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What are SSRIs?
SSRI stands for selective serotonin reuptake inhibitor, and is a group of medicines used in the treatment of depression and anxiety. They work by increasing the availability of the neurotransmitter serotonin in the brain. Serotonin plays an important role in a range of cognitive functions, mood, memory and sleep.