Risk of neurodevelopmental disorders increasesd with maternal anaemia

Anaemia diagnosed earlier in pregnancy is associated with increased risk of development of autism spectrum disorder (ASD), attention-deficit/hyperactivity disorder (ADHD), and particularly intellectual disability (ID) in the offspring, according to results of a recent study.

In the study, the prevalence of ASD, ADHD, and ID was higher among children born to mothers diagnosed with anaemia within the first 30 weeks of pregnancy (ASD: 4.9 percent vs 3.8 percent vs 3.5 percent; ADHD: 9.3 percent vs 7.2 percent vs 7.1 percent; ID: 3.1 percent vs 1.1 percent vs 1.3 percent) compared with mothers with anaemia diagnosed later in pregnancy or mothers not diagnosed with anaemia. [JAMA Psychiatry 2019, doi: 10.1001/jamapsychiatry.2019.2309]

Anaemia diagnosed during the first 30 weeks of pregnancy, but not later, was associated with increased risk of diagnosis of ASD (odds ratio [OR], 1.44; 95 percent confidence interval [CI], 1.13 to 1.84), ADHD (OR, 1.37; 95 percent CI, 1.14 to 1.64), and ID (OR, 2.20; 95 percent CI, 1.61 to 3.01) in the offspring after adjustment for socioeconomic, maternal, and pregnancy-related factors. The strongest association was observed between anaemia and ID without co-occurring ASD (OR, 2.72; 95 percent CI, 1.84 to 4.01), after adjustment.

The association between early anaemia diagnosis and risk of ASD (OR, 2.25; 95 percent CI, 1.24 to 4.11) and ID (OR, 2.59; 95 CI, 1.08 to 6.22) was also apparent in matched sibling analysis. A modest proportion (2.2 percent to 43.1 percent) of the risk of developing these disorders was mediated by obstetric complications such as preterm birth.  

The cohort study enrolled 532,232 nonadoptive individuals (mean age, 17.6 years; male, 51.3 percent) between 6 and 29 years of age at the end of follow-up and their 299,768 mothers. Individuals were eligible if mothers had registered diagnoses of anaemia during pregnancy with gestational timing of first recorded anaemia diagnoses (≤30 weeks or >30 weeks) to assess potential critical windows of development.

Iron demand increases in pregnancy and iron deficiency aenamia is common among pregnant women. Severe maternal iron deficiency can lead to foetal iron deficiency, conferring a risk of developing brain structures, neurotransmitter systems and myelination that are implicated in the aetiology of ASD, ADHD as well as ID. Adverse obstetric outcomes caused by maternal anaemia might also mediate the association.   

“Given that iron deficiency and anaemia are common among women of childbearing age, our findings emphasize the importance of early screening for iron status and nutritional counselling in antenatal care,” concluded the authors.