New study links anemia in early pregnancy to higher autism risk in children

Women who suffer from anemia earlier in pregnancy may give birth to children who have a higher risk of ADHD and autism.

New European research has found that women who suffer from anemia in early pregnancy, a condition which is usually more common in late pregnancy, may give birth to children who have a higher risk of autism and attention deficit hyperactivity disorder (ADHD).

Carried out by researchers at the Karolinska Institutet, Sweden, the new study looked at 532,232 Swedish children and their 299,768 mothers to look at what effect the timing of an anemia diagnosis during pregnancy had on the fetus's neurodevelopment. In particular, the researchers wanted to investigate if there was an association between an earlier diagnosis of anemia and a higher risk of intellectual disability (ID), autism, and ADHD in children.

The findings, published in the journal JAMA Psychiatry, showed that children born to mothers who had anemia diagnosed at the 30th week of pregnancy or before had a higher risk of developing autism, ADHD, and intellectual disability, compared to children born to mothers diagnosed with anemia later in pregnancy and mothers who were not diagnosed at all. 

More specifically, of the children born to mothers who suffered from anemia at week 30 or earlier, 4.9 percent were diagnosed with autism, compared to 3.5 percent of children born to healthy mothers. In addition, 9.3 percent were diagnosed with ADHD, and 3.1 percent were diagnosed with intellectual disability, compared to 7.1 percent and 1.3 percent, respectively, of children born to non-anemic mothers.

After taking into account potentially influencing factors such as the mother's age and income level, the researchers concluded that children born to mothers with early anemia had a 44 percent higher chance of autism 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. 

However, the same associations were not found between these health conditions and anemia diagnosed toward the end of pregnancy, which the researchers say highlights the importance of early screening to determine a woman's iron status and if she needs to adjust her iron intake.

The researchers noted that around 15 to 20 percent of pregnant women worldwide suffer from iron deficiency anemia, which is when the blood's ability to carry oxygen is reduced, often due to a lack of iron. However, the large majority of anemia diagnoses are made toward the end of pregnancy, as the rapidly growing fetus takes up a lot of iron from the mother.

In this study, less than 1 percent of all mothers were diagnosed with early anemia.

"A diagnosis of anemia earlier in pregnancy might represent a more severe and long-lasting nutrition deficiency for the fetus," says Renee Gardner, 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 National Institute of Health in the US recommends 18 mg of iron per day for adult women and 27 mg per day during pregnancy. However, as excessive iron intake can be toxic, pregnant women should discuss their iron intake with their midwife or doctor.