Relation of Severity of Maternal Hypothyroidism to Cognitive Development of Offspring

Abstract

Background—An association between maternal subclinical hypothyroidism and low intelligence quotient (IQ) in the oVspring has recently been shown. Objective—To provide evidence for the causality of the association by testing the hypothesis that severity of maternal hypothyroidism correlates inversely with IQ of the oVspring. Methods—IQ scores were compared among 8 year old oVspring of 124 control mothers whose thyroid stimulating hormone (TSH) concentrations were 99.85th percentile. Results—Mean (SD) IQs for each group of children (in ascending order of maternal TSH concentration) were 107 (13), 102 (15), and 97 (14). The diVerence between the extremes was significant (p = 0.003). The percentage of children with IQs > 1 SD below the control mean was 15, 21, and 50 respectively (p = 0.003). The odds ratio of having an I Q>1S Dbelow the control mean, after controlling for socioeconomic status, was 4.7 (p = 0.006) for the third group compared with the controls. Conclusions—The inverse correlation between severity of maternal hypothyroidism and IQ of the oVspring supports a causal relation and makes the need to screen for and treat pregnant women for hypothyroidism even more compelling. (J Med Screen 2001;8:18‐20)