Association of Prenatal Maternal Anemia With Neurodevelopmental Disorders

Question Is maternal anemia during pregnancy associated with risk of 3 commonly co-occurring neurodevelopmental disorders: autism spectrum disorder, attention-deficit/hyperactivity disorder, and intellectual disability? Findings In this cohort study of 532232 nonadoptive Swedish children and their 299768 mothers, anemia diagnosed earlier in pregnancy (<= 30 weeks) was significantly associated with increased offspring risk of autism spectrum disorder, attention-deficit/hyperactivity disorder, and intellectual disability. These associations were not apparent for anemia diagnosed later in pregnancy. Meaning The findings suggest that maternal anemia occurring during early pregnancy is associated with increased risk for autism spectrum disorder, attention-deficit/hyperactivity disorder, and in particular, intellectual disability, emphasizing the importance of early screening for iron status and nutritional counseling in antenatal care. Importance Given the critical role that iron plays in neurodevelopment, an association between prenatal iron deficiency and later risk of neurodevelopmental disorders, such as autism spectrum disorder (ASD), attention-deficit/hyperactivity disorder (ADHD), and intellectual disability (ID), is plausible. Objective To test the a priori hypothesis that anemia diagnosed in mothers during pregnancy is associated with an increased risk of ASD, ADHD, and ID in offspring and that the magnitude of the risk varies with regard to the timing of anemia in pregnancy. Design, Setting, and Participants This cohort study used health and population register data from the Stockholm Youth Cohort to evaluate 532232 nonadoptive children born from January 1, 1987, to December 31, 2010, in Sweden, with follow-up in health registers until December 31, 2016. Data analysis was performed from January 15, 2018, to June 20, 2018. Exposures Registered diagnoses of anemia during pregnancy. Gestational timing of the first recorded anemia diagnosis (<= 30 weeks or >30 weeks) was considered to assess potential critical windows of development. Main Outcomes and Measures Registered diagnoses of ASD, ADHD, or ID or co-occurring combinations of these disorders. Results The cohort included 532 232 individuals (272 884 [51.3%] male) between 6 and 29 years of age at the end of follow-up (mean [SD] age, 17.6 [7.1] years) and their 299 768 mothers. The prevalence of ASD, ADHD, and ID was higher among children born to mothers diagnosed with anemia within the first 30 weeks of pregnancy (4.9% ASD, 9.3% ADHD, and 3.1% ID) compared with mothers with anemia diagnosed later in pregnancy (3.8% ASD, 7.2% ADHD, and 1.1% ID) or mothers not diagnosed with anemia (3.5% ASD, 7.1% ADHD, and 1.3% ID). Anemia 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% CI, 1.13-1.84), ADHD (OR, 1.37; 95% CI, 1.14-1.64), and ID (OR, 2.20; 95% CI, 1.61-3.01) in offspring in models that included socioeconomic, maternal, and pregnancy-related factors. Early anemia diagnosis was similarly associated with risk of ASD (OR, 2.25; 95% CI, 1.24-4.11) and ID (OR, 2.59; 95% CI, 1.08-6.22) in a matched sibling comparison. Considering mutually exclusive diagnostic groups, we observed the strongest association between anemia and ID without co-occurring ASD (OR, 2.72; 95% CI, 1.84-4.01). Associations of these disorders with anemia diagnosed later in pregnancy were greatly diminished. Conclusions and Relevance In contrast to maternal anemia diagnosed toward the end of pregnancy, anemia diagnosed earlier in pregnancy was associated with increased risk of the development of ASD, ADHD, and particularly ID in offspring. Given that iron deficiency and anemia are common among women of childbearing age, our findings emphasize the importance of early screening for iron status and nutritional counseling in antenatal care. This cohort study examines whether maternal anemia during pregnancy is associated with risk of autism spectrum disorder, attention-deficit/hyperactivity disorder, and intellectual disability in youths.