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Pregnancy and Lactation

Poster Session: Spotlight Session - Medications in Pregnancy and Lactation

(AD) Association of Maternal Levothyroxine Use During Pregnancy with Offspring Birth and Neurodevelopmental Outcomes

Sunday, August 28, 2022

8:00 AM – 6:00 PM CEST

Location: Hall E South

Publication Number: 1028

Presenting Author(s)

Mengqin Ge
– The University of Hong Kong, Hong Kong, Hong Kong

Co-Author(s)

Edmund CL Cheung
– The University of Hong Kong, Hong Kong, Hong Kong
Kenneth Man, PhD
– Lecturer in Pharmacoepidemiology and Medication Safety, University of Hong Kong, London, United Kingdom
Patrick Ip
– Department of Paediatrics and Adolescent Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, Hong Kong
Wing Cheong Leung
– Department of Obstetrics and Gynecology, Kwong Wah Hospital, Hong Kong, Hong Kong
Gloria Li
– Department of Health Technology and Informatics, Faculty of Health and Social Sciences, The Hong Kong Polytechnic University, Hong Kong
Annie Kung
– Department of Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, Hong Kong
Ching-Lung Cheung
– entre for Safe Medication Practice and Research, Department of Pharmacology and Pharmacy, Li Ka Shing Faculty of Medicine, Hong Kong, Hong Kong
Ian Wong
– Professor, Centre for Safe Medication Practice and Research, Department of Pharmacology and Pharmacy, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China, Hong Kong

Background: The influence of maternal levothyroxine treatment during pregnancy remains unclear.

Objectives: To evaluate the associations of maternal levothyroxine treatment during pregnancy with the birth and neurodevelopmental outcomes in offspring.

Methods: Design, Setting, and Participants: This population-based cohort study was conducted among pregnant women using the Hong Kong Clinical Data Analysis and Reporting System. Mother-child pairs in Hong Kong from 2001 to 2015 were included and children were followed up till 2020. Mothers who were exposed to anti-thyroid drugs, thyroidectomy, or radioactive iodine therapy were excluded.
Exposure: Levothyroxine treatment during pregnancy.
Main Outcomes Measures: Preterm birth and small for gestational age (SGA) were included as birth outcomes. Attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD) were included as neurodevelopmental outcomes.
Statistical Analysis: Odds ratios (OR) or hazard ratios (HRs) with a 95% confidence interval (CI) were evaluated to assess the association of gestational levothyroxine use with offspring birth and neurodevelopmental outcomes respectively, using propensity score fine-stratification weighting and Cox proportional hazards regression model.

Results: Among 422,156 mother-child pairs, 2,125 children were born from mothers exposed to levothyroxine during pregnancy. A significantly increased risk of preterm birth was observed in children with maternal levothyroxine exposure during pregnancy, when compared to mothers who had no history of thyroid-related diagnoses or prescriptions (weighted OR [wOR]: 1.22, 95% CI: 1.07, 1.39). Similarly, an increased risk of preterm birth was found among children of gestational levothyroxine users, when compared to children of mothers who had used levothyroxine before but stopped during pregnancy (wOR: 2.16, 95%CI: 1.09, 4.25). Sensitivity analysis by excluding mothers exposed to psychotropic or antiepileptics medications before or during pregnancy also indicated a similar increased risk of preterm birth regarding the gestational use of levothyroxine (wOR: 1.26, 95% CI: 1.10, 1.45). No significant association was observed for the risk of SGA, ADHD, and ASD.

Conclusions: Gestational levothyroxine treatment may lead to an increased risk of preterm birth but not SGA, ADHD, or ASD in offspring. Our findings provided support for the current guidelines on the cautious use of levothyroxine treatment during pregnancy.