Association Between Maternal Hypothyroidism During Pregnancy and Childhood Obesity
There is inconsistent evidence regarding the association between maternal hypothyroidism during pregnancy and childhood obesity, with recent meta-analysis data showing no significant association between maternal hypothyroidism and offspring obesity (OR 1.04,95% CI 0.64,1.70). 1
Current Evidence on Maternal Hypothyroidism and Offspring Obesity
The most recent systematic review and meta-analysis (2024) found no statistically significant association between maternal hypothyroidism during pregnancy and obesity in offspring under 18 years of age 1
A 2021 cohort study similarly found no association between maternal hypothyroidism in pregnancy and child overweight (adjusted risk ratio: 1.31,95% CI: 0.86-1.97) or obesity (adjusted risk ratio: 1.25,95% CI: 0.76-2.05) at 7 years of age 2
While there is no strong evidence for obesity specifically, maternal hypothyroidism appears to be independently associated with broader pediatric endocrine morbidity in offspring (adjusted hazard ratio = 1.92,95% CI: 1.08-3.4) 3
Potential Mechanisms and Related Findings
Maternal obesity (rather than hypothyroidism itself) is associated with alterations in both maternal and neonatal thyroid hormone levels, with increasing maternal obesity linked to higher free T3 levels in both mother and neonate 4
Both maternal and neonatal free T3 levels have been significantly associated with birthweight (β = 0.155, P = 0.027 and β = 0.171, P = 0.018, respectively), suggesting a potential pathway for metabolic programming 4
Some evidence suggests maternal hypothyroidism may be associated with increased risk of hypertension and glucose dysregulation in offspring, even if not directly linked to obesity 1
Clinical Implications
Despite the lack of strong evidence linking maternal hypothyroidism to offspring obesity specifically, treatment of maternal hypothyroidism during pregnancy is still recommended for other important reasons 5:
Pregnant women with elevated TSH should be treated with levothyroxine to restore TSH to reference range (≤2.5 mIU/L for first trimester and ≤3 mIU/L for second and third trimesters) 5
Monitoring and Management
TSH levels should be monitored every 4 weeks until stable, then checked every trimester 5
Levothyroxine requirements often increase during pregnancy due to increased metabolic demands 5
Women planning pregnancy who have elevated TSH should be treated before conception to optimize thyroid function 5
Limitations of Current Evidence
Most studies on this topic were conducted outside North America with varying follow-up periods (6-20 years) 1
The relationship between maternal thyroid function and offspring metabolic outcomes is complex and may involve multiple pathways beyond direct hormonal effects 4, 3
There may be sex-specific effects in how maternal metabolic status affects offspring, with some evidence suggesting girls may be more responsive to maternal nutritional status than boys 6