Thyroxine dose adjustment during pregnancy
A Dawson1, JM Ng1, A Wakil1, R Krishnan2, Y Igzeer2, EA Masson1, BA Allan1 & S W Lindow2
Background: Thyroid hormone is essential in foetal neurological development and thyroid hormone deficiency in pregnant women has been linked to lower intelligence quotient and underperformance in their children later in life. Thyroid hormone requirement increases during pregnancy by approximately 50% in the first trimester. We audited our practice of increasing thyroid hormone dose at booking and thereafter in pregnant women attending our combined obstetric medical clinic.
Patients and methods: Retrospective audit of all pregnant women with pre-existent hypothyroidism who delivered between May and August 2008. Seventeen patients were included.
Results: At antenatal booking there were 8 patients with TSH above 2 mU/l of whom only one had the dose of thyroxine increased. However, 6 more had their thyroxine dose increased as they advanced in pregnancy by the obstetricmedical clinic. The percentage by which the thyroxine was increased ranged between 20 and 100%. Of those who did not have their thyroxine dose altered, 2/10 had suppressed TSH, 6/10 had TSH<2 mU/l, 1/10 had TSH=>2 and < 4.5 while one had very high TSH, probably due to non compliance.
Conclusion: This audit illustrates over half of women with hypothyroidism are attending antenatal booking with a TSH level above the recommended range (>2.0 mU/l). Additionally dose adjustment was often not done until subjects were seen in secondary care (later in the first trimester).
Recommendations: (1) Educate primary care and maternity services that target range for TSH in pregnancy is 0.5 to 2.0 mU/l. (2) Educate midwives and GPs about the need to increase thyroxine dose during the initial stages of pregnancy. Printing leaflets directed to hypothyroid women of child bearing age with the intent to become pregnant or those who have just become pregnant may be beneficial.