You probably know how hard it can be to settle down at night when you are pregnant.
Most expectant mothers put it down to a growing belly or an awkward sleeping position.
For some women, though, the trouble comes from somewhere else entirely.
Pregnant women who develop restless legs syndrome in their third trimester have about three times the usual risk of perinatal depression.
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That is the main finding of a study of 2,435 women by researchers at the University of Tokyo, published in the Journal of Clinical Sleep Medicine in October 2026.
What restless legs syndrome actually feels like
Restless legs syndrome is a neurological condition. It brings an uncomfortable urge to move the legs, usually in the evening or at night, that eases only when you move.
Many women develop it during pregnancy and lose it again after birth, according to the National Institute of Neurological Disorders and Stroke.
The sensations are hard to pin down. Some women describe a crawling feeling, others a buzzing or a pulling.
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It almost always gets worse at rest, which is why it so often disrupts sleep.
The risk only shows up in the third trimester
Timing turned out to matter a lot. Women screened at 32 weeks who met the criteria for restless legs syndrome had a sharply higher chance of a major depressive episode.
The same screening earlier in pregnancy, in the second trimester, did not produce the same signal.
The team, led by Dr. Kazuhide Tezuka of the University of Tokyo, recommends asking about restless legs symptoms again at third-trimester visits.
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Screening only at the first prenatal appointment misses women heading toward depression.
Perinatal depression is a major depressive episode during pregnancy or in the months after birth.
About 1 in 8 women report symptoms of it after a recent live birth, according to the CDC, and the condition is often missed.
Why iron may link the two problems
The researchers also pointed to a plausible shared cause. Iron deficiency commonly develops in the third trimester and may feed both the leg symptoms and the mood changes, they wrote.
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Iron deficiency anemia is a well-known trigger for restless legs syndrome, the NINDS notes.
That matters because iron status is something a prenatal provider can check with a blood test, and low iron in pregnancy is routinely treatable with supplements under medical supervision.
Women who notice an irresistible urge to move their legs at night in late pregnancy can bring it up at their next prenatal visit and ask about iron testing and about depression screening.
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This article is made and published by Mie Hermansen, who may have used AI in the preparation.