Introduction: Maternal hypothyroidism is associated with an increased risk of complications both to the pregnant mother and the developing fetus. The 2007 American Endocrine Society Guidelines recommend a rapid titration of thyroxine dose to attain a target TSH concentration of ≤2.5 µU/mL in the 1st trimester (≤3 µU/mL in the 2nd and 3rd trimesters). Objectives Our aims were to assess the adequacy of thyroxine replacement in pregnant women with hypothyroidism and the thyroxine dose increment required. Methods A retrospective audit was performed on 38 women with maternal hypothyroidism referred to the combined endocrine antenatal clinic between June 2008 and December 2009.
Results: The majority (71%) had presumed autoimmune hypothyroidism pre-pregnancy, 10% were post-thyroidectomy, 11% post-radioiodine, 3% post-radioiodine & thyroidectomy. Five per cent had newly diagnosed subclinical hypothyroidism in pregnancy. The median gestational age at the 1st midwife-led antenatal visit was 11 weeks (interquartile range 6.512). The majority of patients were given their 1st combined endocrine antenatal clinic appointment in the 2nd trimester (median 15 weeks; interquartile range 1317.25) with 21% being advised to increase their thyroxine dose prior to clinic (13% endocrinologist, 5% GP, 3% obstetrician). Thyroxine dose adjustment was initiated by an endocrinologist in 92% of cases. The median gestational age at 1st dose increment was 14 weeks. Dose adjustment was not required in 22% of patients. Target TSH was first achieved at a median of 20 weeks (interquartile range 10.7525.25). Thyroxine dose increments during pregnancy were similar for both autoimmune and other aetiologies (median 25%).
Conclusion: Our current management of maternal hypothyroidism is suboptimal, with delayed titration of thyroxine, partly because of the timing of presentation to the midwife-led antenatal clinic and consequently late referrals to endocrinology. Earlier assessment of thyroid function and dose titration could be achieved by increased primary care involvement and better patient education.
Declaration of interest: There is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.
Funding: No specific grant from any funding agency in the public, commercial or not-for-profit sector.