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Early maternal anemia tied to intellectual disability, ADHD and autism

Karolinska Institutet

late pregnancy

The timing of anaemia - a common condition in late pregnancy - can make a big difference for the developing fetus, according to new study. Researchers found a link between early anaemia and increased risk of autism, ADHD and intellectual disability in children.

FAB RESEARCH COMMENT:

Anaemia in pregnancy is most commonly caused by maternal iron deficiency, and affects 15-20% of pregnancies worldwide.

Iron deficiency in early life is already known to have the potential to cause lifelong impairments of brain development and function - raising risks for intellectual and other cognitive impairments and for behavioural disorders including ADHD or Autism Spectrum Disorders (ASD).

However, the impact of iron deficiency (or any other essential nutrient deficiencies) on the unborn child is also known to reflect both the timing and the severity of the deficiency - as well as numerous other factors that may either magnify, or help to compensate for, its effects.

In this new study from Sweden, maternal anaemia in early to mid-pregnancy (before week 30) was found to predict significantly increased risks for ADHD, ASD, and intellectual disability (ID) in the resulting children - while anaemia that only occurred in late pregnancy did not.

  • Controlling for other known risk factors, the increased risks for children born to mothers with early anaemia vs those without anaemia were 37% for ADHD, 44% for ASD and 120% for intellectual disability. 

As the researchers emphasise, these findings highlight the importance of early screening of iron status and nutritional counseling for all mothers-to-be in order to reduce rates of maternal anaemia, and improve child developmental outcomes.  

They also flagged the need for more research trials to assess the relative benefits vs risks of iron supplementation during pregnancy - as an excess of iron can also be harmful.

For more information on iron in pregnancy, please see the following lists of articles, which are regularly updated:


For details of this research study, see:


See also:

18 Sept 2019 - MedXpress

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The timing of anemia - a common condition in late pregnancy - can make a big difference for the developing fetus, according to research at Karolinska Institutet published in JAMA Psychiatry.

The researchers found a link between early anemia and increased risk of autism, ADHD and intellectual disability in children. Anemia discovered toward the end of pregnancy did not have the same correlation.

The findings underscore the importance of early screening for iron status and nutritional counseling.

An estimated 15 to 20 percent of pregnant women worldwide suffer from iron deficiency anemia, a lowered ability of the blood to carry oxygen that is often 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 impact the timing of an anemia diagnosis had on the fetus' neurodevelopment, in particular if there was an association between an earlier diagnosis in the mother and the risk of intellectual disability (ID), autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD) in the child.

Overall, very few women are diagnosed with anemia early in pregnancy. In this study of nearly 300,000 mothers and more than half a million children born in Sweden between 1987-2010, less than 1 percent of all mothers were diagnosed with anemia before the 31st week of pregnancy. Among the 5.8 percent of mothers who were diagnosed with anemia, only 5 percent 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 autism and ADHD and a significantly higher risk of intellectual disability compared to healthy mothers and mothers diagnosed with anemia later in pregnancy.

Among the early anemic mothers, 4.9 percent of the children were diagnosed with autism compared to 3.5 percent of children born to healthy mothers, 9.3 percent were diagnosed with ADHD compared to 7.1 percent; and 3.1 percent were diagnosed with intellectual disability compared to 1.3 percent of children to non-anemic mothers.

After considering other factors such as income level and maternal age, the researchers concluded that the risk of autism in children born to mothers with early anemia was 44 percent higher compared to children with non-anemic mothers, the risk of ADHD was 37 percent higher and the risk of intellectual disability was 120 percent higher.

Even when compared to their siblings, children exposed to early maternal anemia were at higher risk of autism and intellectual disability. 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, project coordinator at the Department of Public Health Sciences at Karolinska Institutet 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 to a later exposure."

The researchers also noted that early anemia diagnoses were associated with infants being born small for gestational age while later anemia diagnoses were associated with infants being born large for 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 the 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 counseling 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.