Background: Severe maternal hypothyroidism during pregnancy may be associated with delayed development and lower IQ in the foetus. BES (2007) and NICE (2011) guidelines recommend maintaining TSH<2.5 mU/l with monitoring of maternal thyroid function test (TFT) 4 weekly, especially in the first trimester.
Aim and methods: A retrospective study on all pregnant women with established hypothyroidism attending the Joint Antenatal Clinic (JANC) at Liverpool Womens Hospital from April 2017 to March 2018, using data from online medical records and GPs referral letters.
Result: 77 patients attended. 37 (48.6%) had TFTs checked in the 6 month period prior to conception. 46% of these had TFTs within the normal range for pregnant women (TSH<2.5 mU/l). Of these, 39% developed TSH >2.5 mU/l once they had conceived. Post conception, 34.2% (of 77) had not had TFTs checked till their review at JANC. In 52% (of 77), TSH was not in the recommended range for pregnancy at the 1st TFT check. Of those with TSH outside the recommended range, 76.7% (43.4% of whole cohort) required adjustment of Levothyroxine dose at 1st JANC visit. 87% of the whole cohort required dose adjustment at least once during pregnancy. The average increase in dose was 55% (range 17400%). TFTs were checked on average 5 times during pregnancy, with average gestation of 32 weeks. The newer American Thyroid Association guideline (2017) recommends TSH<4 mU/l during pregnancy. Based on that we would have needed to adjust the dose of levothyroxine preconception and on the first JANC visit in 54.5% and 37% of patients (n=77) respectively.
Conclusion: A significant proportion of pregnant women with hypothyroidism require alteration of thyroid medication during pre during and post pregnancy. This increasing workload is best undertaken by assessment in a joint clinic, and subsequent telephone follow up.