Aims: In 2005 we defined a specific reference range for TSH in our pregnant population. We have assessed whether this has resulted in changed management of treated hypothyroidism in pregnant.
Methods: The management of 73 mothers (Group 1) between January 2000 and July 2005 was compared to that of 67 mothers (Group 2) between August 2005 and December 2009. The upper limit of normal for TSH was 4.5 mU/l till July 2005; the specific TSH range defined for pregnancy was 0.11.82 mU/l at booking and 0.032.15 mU/l at 28 weeks. For pragmatic reasons an upper level of 2.5 mU/l was used for this study.
Results: The mean±S.D. of TSH measurements during pregnancy were Gp 1: 4.4±0.91; Gp2: 4.7±1.13. The number of increased TSH levels were Gp1: 1.3±1.57; Gp2: 1.8±1.7. The number of increases in levothyroxine doses were Gp1: 0.9±1.06; Gp2: 1.2±0.91. The incremental increase in levothyroxine was Gp1: 52.4 μg ±37.77; Gp2: 43.4 μg ±26.23. The mean TSH levels at booking were Gp1: 6.96±12.99 (number >4.5=13; >2.5=24); Gp2: 5.2±7.17 (number >2.5=26). The mean TSH levels at 28 weeks were Gp1: 1.95±2.46 (number >4.5=6; >2.5=13); Gp2: 2.35±3.53 (number >2.5=18).
Conclusions: TSH testing and levothyroxine increases were increased following the introduction of a specific TSH range in pregnancy, but a significant number were hypothyroid by this lower reference range at both booking and 28 weeks. Thus biochemical management remained suboptimal.