Newly published research from the Karolinska Institute underscores the important of early anemia screening during pregnancy.1

The timing of anemia—a common condition in late pregnancy—can make a big difference for the developing fetus, according to the new study. The researchers found a link between early anemia and increased risk of attention-deficit/hyperactivity disorder (ADHD), autism, and intellectual disability in the child. Anemia discovered toward the end of pregnancy did not have the same correlation.

An estimated 15% to 20% of pregnant women worldwide suffer from iron deficiency anemia, a lowered ability of the blood to carry oxygen that is caused by a lack of iron. The vast majority of anemia diagnoses are made toward the end of pregnancy, when the rapidly growing fetus takes up a lot of iron from the mother.

In the current study, the researchers examined what effect the timing of an anemia diagnosis had on the neurodevelopment of the fetus. In particular, they sought to determine whether there was an association between an earlier diagnosis in the mother and the risk of ADHD, autism spectrum disorder, or intellectual disability in the child.

Very few women are diagnosed with anemia early in pregnancy. The Karolinska Institute study encompassed nearly 300,000 mothers and more than 500,000 children born in Sweden between 1987 and 2010, and found that less than 1% of all mothers were diagnosed with anemia before the 31st week of pregnancy. Among the 5.8% of mothers who were diagnosed with anemia, only 5% received their diagnosis early on.

The researchers found that children born to mothers with anemia diagnosed before the 31st week of pregnancy had a somewhat higher risk of developing ADHD and autism, and a significantly higher risk of intellectual disability, compared with the children of healthy mothers and mothers diagnosed with anemia later in pregnancy. Among the children of early anemic mothers, 9.3% were diagnosed with ADHD compared with 7.1% of the children born to healthy mothers; 4.9% were diagnosed with autism compared with 3.5% of children born to healthy mothers; and 3.1% were diagnosed with intellectual disability compared with 1.3% of children born to non-anemic mothers.

After considering other factors such as income level and maternal age, the researchers concluded that the risk of ADHD in children born to mothers with early anemia was 37% higher than for children born to non-anemic mothers; the risk of autism was 44% higher; and the risk of intellectual disability was 120% higher. Even when compared with their siblings, children exposed to early maternal anemia were at higher risk of autism and intellectual disability.


Renee Gardner, PhD, Karolinska Institute.

Importantly, anemia diagnosed after the 30th week of pregnancy was not associated with a higher risk for any of these conditions.

“A diagnosis of anemia earlier in pregnancy might represent a more severe and long-lasting nutrition deficiency for the fetus,” says Renee Gardner, PhD, assistant professor of public health sciences at the Karolinska Institute, and the study’s lead researcher. “Different parts of the brain and nervous system develop at different times during pregnancy, so an earlier exposure to anemia might affect the brain differently compared with a later exposure.”

The researchers also noted that early anemia diagnoses were associated with infants being born small for their gestational age, while later anemia diagnoses were associated with infants being born large for their gestational age. Babies born to mothers with late-stage anemia are typically born with a good iron supply, unlike babies born to mothers with early anemia.

Although the researchers couldn’t disentangle anemia caused by iron deficiency from anemia caused by other factors, iron deficiency is by far the most common cause of anemia. The researchers say the findings could be a result of iron deficiency in the developing brain and may thus support a protective role for iron supplementation in maternity care. The researchers emphasize the importance of early screening for iron status and nutritional counselling but note that more research is needed to find out if early maternal iron supplementation could help reduce the risk of neurodevelopmental disorders in children.

Adult women typically need 15 mg of iron per day, though needs may increase later in pregnancy. Since excessive iron intake can be toxic, pregnant women should discuss their iron intake with their midwife or doctor.


  1. Wiegersma AM, Dalman C, Lee BK, Karlsson H, Gardner RM. Association of prenatal maternal anemia with neurodevelopmental disorders. JAMA Psychiatry. Epub ahead of print, September 18, 2019; doi: 10:1001/jamapsychiatry.2019.2039.

Featured image:

Study coauthors Renee Gardner, PhD (left), and Aline Marileen Wiegersma, MS, Karolinska Institute.