Objective Previous studies suggested maternal hypothyroidism during pregnancy to be associated with cognitive impairment of the offspring. Scarce data exist regarding long-term endocrine health of the offspring. This study was aimed to assess whether children born to mothers with hypothyroidism during pregnancy are at an increased risk for long-term endocrine morbidity. Study Design A retrospective population-based cohort study compared long-term endocrine morbidity of children born between the years 1991 and 2014 to mothers with and without hypothyroidism. Multiple gestations, fetuses with congenital malformations, and women lacking prenatal care were excluded. Hospitalizations of the offspring up to the age of 18 years involving endocrine morbidity were evaluated according to a predefined set of ICD-9 codes. Kaplan–Meier's survival curves were used to compare the cumulative risk and a Cox multivariable model was used to adjust for confounders. Results During the study period, 217,910 deliveries met the inclusion criteria; 1.1% of which were with maternal hypothyroidism (n = 2,403). During the follow-up period, the cumulative incidence of endocrine morbidity among children born to mothers with hypothyroidism was 27 per 1,000 person-years and 0.47 per 1,000 person-years in the comparison group (relative risk: 2.14; 95% confidence interval [CI]: 1.21–3.79). The Kaplan–Meier's survival curve demonstrated a significantly higher cumulative endocrine morbidity in children born to mothers with hypothyroidism (log-rank test, p = 0.007). In the Cox regression model controlled for maternal age, birth weight, preterm birth, maternal diabetes, hypertensive disorders of pregnancy, induction of labor, and mode of delivery, maternal hypothyroidism was found to be independently associated with pediatric endocrine morbidity in the offspring (adjusted hazard ratio = 1.92, 95% CI: 1.08–3.4, p = 0.025). Conclusion Maternal hypothyroidism appears to be independently associated with long-term pediatric endocrine morbidity of the offspring. This study was presented in part at the 38th SMFM Annual Meeting, January 29–February 3, 2018, Dallas, TX. The authors are responsible for study design; collection, analysis, and interpretation of data; writing of the report; and the decision to submit the report for publication.

Background/Objectives: Overt hypothyroidism during pregnancy has been linked to adverse outcomes, including preterm birth, low birth weight, and impaired fetal neurocognitive development. This study aimed to evaluate pregnancy complications in women with overt hypothyroidism (TSH ≥ 10) through a cross-sectional study. Methods: Data from 259,897 live-birth pregnancies (2013–2022) from Clalit Health Services (CHS) were analyzed. The study included all CHS-insured women aged ≥ 18 years with available TSH results during pregnancy. Overt hypothyroidism was defined as a mean TSH ≥ 10 mIU/L, while the euthyroid reference group had TSH levels < 4 mIU/L and no history of hypothyroidism or levothyroxine use. Cases of overt hypothyroidism were matched with 15 controls using propensity score-based matching. Covariates included maternal age, ethnicity, socioeconomic status, IVF use, recurrent pregnancy loss, and smoking. Pregnancy complications were compared between groups using descriptive statistics and univariate analysis. A quasi-Poisson regression model was used to assess complication risk in overt hypothyroidism versus matched controls. Results: The final analysis included 9125 euthyroid and 611 overt hypothyroid pregnancies, with comparable baseline characteristics between groups. No significant differences were found in maternal age, ethnicity, socioeconomic scores, IVF rates, recurrent pregnancy loss, diabetes, smoking, gestational age at delivery, or rates of preterm birth, pre-eclampsia, gestational diabetes, cesarean section, and intrauterine growth restriction. Overall, overt hypothyroidism was not associated with increased complications. Sensitivity analyses using maximum TSH levels during pregnancy showed a slightly elevated risk for pregnancy complications (IRR 1.1, CI 1.04–1.18; p = 0.002). Conclusions: Overt hypothyroidism was not associated with an increased risk of adverse pregnancy outcomes when adjusted for confounding factors, suggesting that treatment decisions should be made on an individual basis.