Ms Katherine Tran1,2, Associate Professor Terrence Diamond1,2, Dr Frederic Phan1,2, Professor Anthony O'Sullivan1,2
1Department of Endocrinology, St George Hospital, Sydney, Australia, 2School of Clinical Medicine, UNSW Medicine and Health, Sydney, Australia
Biography:
Katherine is a fourth-year medical student undertaking a full-time research year at UNSW.
Abstract:
Background: Overt hypothyroidism during pregnancy is associated with adverse foetal and maternal outcomes, the most deleterious being impaired neurocognitive development of progeny. Observational studies are reporting the association between subclinical hypothyroidism (SCH) and similar adverse effects. What remains unclear is the role of thyroxine therapy in the improvement of these outcomes. In the absence of clear guidelines, the decision to treat remains at the discretion of the practitioner.
Objectives: To investigate the impact of SCH on maternal and neonatal outcomes in subjects with no prior history of thyroid disease and analyse the effect of Levothyroxine therapy on these outcomes.
Methods: We performed a non-randomised retrospective cohort study of 200 pregnant women with SCH presenting to St George Hospital from 2017-2023. Data was obtained from electronic medical records. The study population comprised of participants who either received thyroxine to normalise TSH to 0.1-2.5 mIU/L (n=150) or did not (n=50). Outcomes were: (1) maternal – gestational diabetes, hypertensive disorders, postpartum and antepartum haemorrhage, cumulative blood loss, maternal complications, mode of labour and delivery and (2) neonatal – gestational age, prematurity, APGAR scores, birth weight, birth complications, foetal distress, need for high care. Data analysis was performed using Pearson’s Chi-square test of independence and multinomial and logistic regression models.
Results: Using the diagnostic TSH range 2.5-9.9 mIU/L no significant differences in gestational diabetes (OR=0.33, p=0.25), hypertensive disorders (OR=0.77, p=0.62), postpartum haemorrhage (OR=0.29, p=0.10), antepartum haemorrhage (OR=1.79, p=0.65), maternal complications (OR=1.78, p=0.10), preterm delivery (OR=0.58, p=0.50), newborn complications at birth (OR=0.73, p=0.36), foetal distress (OR=1.51, p=0.30), or need for high care (OR=0.88, p=0.57) were observed between groups. There was no evidence of association between treatment and mode of delivery (x2=0.21, p=0.98) between groups.
Conclusion: These findings suggest that thyroxine has a negligible effect on maternal and neonatal outcomes in pregnant women with SCH.
Keywords
subclinical hypothyroidism, thyroxine replacement, pregnancy outcomes
References
Casey BM, Thom EA, Peaceman AM, Varner MW, Sorokin Y, Hirtz DG, et al. Treatment of Subclinical Hypothyroidism or Hypothyroxinemia in Pregnancy. N Engl J Med. 2017;376(9):815-25.
De Groot L, Abalovich M, Alexander EK, Amino N, Barbour L, Cobin RH, et al. Management of thyroid dysfunction during pregnancy and postpartum: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2012;97(8):2543-65.
Maraka S, Mwangi R, McCoy RG, Yao X, Sangaralingham LR, Ospina NMS, et al. Thyroid hormone treatment among pregnant women with subclinical hypothyroidism: US national assessment. BMJ. 2017;356:i6865.