Anemia in early pregnancy linked with risk for neurodevelopmental disorders

Children born to mothers with iron-deficiency anemia early in pregnancy may be at higher risk for neurodevelopmental disorders, a new study suggests.

In an analysis of data on more than half a million babies born in Sweden, researchers found that anemia in the mother before the 30th week of pregnancy was linked with a heightened risk of disorders including autism, ADHD and intellectual disability.

The study doesn’t prove the anemia causes these problems; it only shows an association. Still, said study coauthor Renee Gardner, the findings suggest “it may be even more important than we have previously understood to boost low iron levels among women who are considering becoming pregnant or who are within the early weeks of pregnancy.” That doesn’t mean women should panic, said Gardner, who studies psychiatric conditions, substance use and social environment at the Karolinska Institute in Stockholm. “It’s important to remember that while anemia is common in pregnancy it’s relatively rare that otherwise healthy women receive this diagnosis before the 30th week of pregnancy.” Anemia is more common later in pregnancy when iron demands of the fetus increase, Gardner said. But when the condition is found after 30 weeks, it’s not associated with an increased risk of neurodevelopmental disorders, she added.

Iron plays a role in the development of the nervous system, Gardner said. “For example, we know that it’s important for neurons making new connections with other neurons and to build the protective coating on the outside of nerve cells that improve signal transmission.” There are other ways low iron early in pregnancy could lead to developmental problems, Gardner said in an email.

“Babies born to mothers who were diagnosed with anemia earlier on tended to be smaller and were more likely to be born preterm,” Gardner said. “The mothers were also more likely to have complicated pregnancies. So, while it’s possible that a lack of iron or other nutrients for a longer period of time during pregnancy directly influences the development of the brain on a molecular level, we also saw some evidence that the complications associated with anemia, such as preterm birth and pre-eclampsia, could explain some of the increased risks that we observed.” As reported in JAMA Psychiatry, Gardner and her colleagues analyzed data from the Stockholm Youth Cohort, a registry of individuals born from 1984 through 2011 who were residing in Stockholm County at any point from 2001 through 2011.

The rates of neurodevelopmental disorders were relatively low both in women with anemia and those with normal iron levels. For example, autism was diagnosed in 4.9% of children born to women with anemia early in pregnancy, 3.8% of those with moms diagnosed with anemia later, and 3.5% of children whose mothers were anemia-free during pregnancy.

Similarly, ADHD was diagnosed in 9.3% of children with moms with anemia early in pregnancy, 7.2% of those with moms with anemia diagnosed later, and 7.1% of those with anemia-free moms.

Intellectual disability was diagnosed in 3.1% of children with mothers who had anemia early in pregnancy versus 1.1% of those whose moms developed anemia later on and 1.3% of kids born to moms without anemia.

Looked at another way, children born to women who had anemia early in pregnancy were 1.44 times more likely to develop autism, 1.37 more likely to develop ADHD and 2.2 times more likely to have intellectual disability compared to children with moms who developed anemia later in pregnancy.

While the new study shows an association between anemia early in pregnancy, “an association is not the same as causation,” said Dr. Nevert Badreldin, an assistant professor of obstetrics and gynecology at Northwestern University’s Feinberg School of Medicine. “It’s hard to assess, based on this information, whether the anemia is in fact creating the association or whether the higher rates of neurodevelopmental disorders are related to something else the women (with anemia early in pregnancy) have in common.” Women should be reassured that the current guidelines recommend screening for anemia at the first prenatal visit, Badreldin said. “So the great majority of women are getting screened early,” she added.