Thyroxine replacement in pregnancy and pre-conception: An audit of patient and GP knowledge of guidelines and current clinical practice in Leicestershire

Nikki Kieffer, Endocrine Nurse Specialist, Department of Diabetes and Endocrinology, Leicester Royal Infirmary

Thyroxine is essential for the development of a baby’s brain and nervous system. In pregnancy the baby’s own thyroid gland only begins to produce thyroid hormones after the 12th week. This means that during the first 12 weeks of pregnancy the only source of thyroxine available to the developing baby is from the mother. It is therefore essential that the mother is on an adequate dose of thyroxine to ensure that there is enough available for both the mother and the developing baby.

Guidelines for the management of hypothyroidism in pregnancy suggest that women on thyroxine replacement should be having the dose of thyroxine adjusted to its optimal level prior to pregnancy or at the latest as soon as they become pregnant. To be sure that the mother is on the right dose of thyroxine replacement during pregnancy it is suggested that, once the thyroxine dose has been adjusted to keep the Thyroid Function Tests (TFTs) within the recommended levels, then TFTs should be checked at least once per trimester (12 weeks).

Whilst we do have a dedicated Endocrine/Antenatal clinic in our hospital it is rare for women on thyroxine to be referred to this clinic until they have been seen by the community midwife at 12 weeks gestation, with the result that they are rarely seen until they are well into their second trimester of pregnancy. It is unclear as to how they are being managed in early pregnancy and by whom. As only very small numbers are referred to the clinic it seems that some women are not being referred at all and it is unclear as to who is managing these patients during their pregnancies. This prompted two questions. The first question is are GPs managing these women and if so are they aware of and using the current guidelines? The second question is whether women on thyroxine are aware of the need to optimise thyroxine before and during pregnancy and whether they are being advised appropriately.

In July 2010 I submitted my idea for a study to look into these questions to the British Thyroid Foundation and was awarded The Evelyn Ashley Smith Award for a Nurse with Specialist Interest in Thyroid disorders. This gave me the funding to be able to carry out this study.

This was done via the Leicestershire Thyroid Register which currently monitors thyroid hormone levels in patients on thyroxine replacement and advises on replacement doses directly to the patient by post. Questionnaires were sent to 100 women of child-bearing age and to their GPs. The women were asked questions to identify whether they had been more closely monitored in pregnancy and whether their dose of thyroxine had been changed during pregnancy, and if so by whom. The GPs were asked about their awareness and use of the guidelines. This initial study showed a distinct lack of knowledge in both GPs and patients. The questionnaires were updated with more specific questions in some areas and were sent out to over 500 women who had not previously been contacted, and to 210 GPs.

65% of the seventy GPs who replied had no knowledge of any guidelines. Only a small percentage was aware of the target values for TFTs during pregnancy and when thyroxine doses should be changed. Nearly half said they would leave monitoring and changes of thyroxine dose to the Endocrine Antenatal clinic – a worry given the late referral to this service.

232 replies were received from the patients. Just under half of these (44%) had either not been pregnant or had not been on thyroxine at the time of pregnancy. Of the remainder about half had been advised to change their dose of thyroxine in pregnancy and about one third had been advised to increase the frequency of thyroid blood tests.

From the replies to these questionnaires it is clear that the knowledge of how to manage thyroxine replacement in pregnant women is poorly understood by GPs and women on thyroxine replacement are often not being managed during their pregnancies as recommended in the guidelines.

As a result of these findings we plan to draw up local guidelines for GPs and to advertise more widely the availability of expert advice from the Endocrine Antenatal Service. We also plan to write a quick guide for women on what to do with their thyroxine replacement when planning a pregnancy and the importance of increased monitoring and adjustment of doses during pregnancy. We plan to send this guide out via the thyroid register.

I am grateful to the British Thyroid Foundation for giving me the opportunity to carry out this study. I would also like to thank Dr James Falconer-Smith for his help in identifying the women eligible for this study from the thyroid register. I am sure that, as a result of this study, hypothyroid women in Leicestershire will benefit from improvements made to the management of women on thyroxine replacement during pregnancy.