O-129 Subclinical hypothyroidism and antithyroid autoantibodies in women with subfertility or recurrent pregnancy loss: a scientific impact paper
Authors: Dhillon-Smith R , Coomarasamy A , Boelaert K , Jeve Y , Maheshwari A 
Published: June 2022

Study question

How should subclinical hypothyroidism (SCH) and autoimmune thyroid disease (ATD) be managed in women with subfertility or recurrent pregnancy loss?

Summary answer

This Royal College of Obstetricians and Gynaecologists (RCOG) scientific impact paper provides evidence based recommendations on the testing for and management of SCH and ATD.

What is known already

Subclinical hypothyroidism and autoimmune thyroid disease have been linked to adverse pregnancy outcomes such as miscarriage and premature birth. There is debate about whether there should be routine testing of thyroid function in both the general population and individuals who are trying for a baby. In addition, the strategies used to manage certain thyroid problems are questioned. Discussions around testing and subsequent management particularly relate to women with a history of subfertility or recurrent pregnancy loss (RPL).

Study design, size, duration

The purpose of this scientific impact paper is to provide evidence based clinical practice recommendations about the controversial subjects of SCH and antithyroid autoantibodies in women with a history of subfertility or RPL. This has been done by reviewing and collating the published evidence and international guidance.

Participants/materials, setting, methods

This body of work is a literature review of published primary studies, systematic reviews and international guidelines relating to the screening for and management of SCH and ATD in women with subfertility or recurrent pregnancy loss. Recommendations for practice and areas for further research have been identified.

Main results and the role of chance

Population-trimester and laboratory-specific reference ranges for serum thyroid stimulating hormone (TSH) and free thyroxine (fT4) should be applied when defining SCH. Untreated mild–moderate SCH (TSH 4.0-10.0mIU/l) is associated with early pregnancy loss and there is low-quality evidence that levothyroxine (LT4) treatment of such women is associated with improved pregnancy and live birth rates.

Routine preconception TSH and fT4 testing should be offered to women with history of RPL or subfertile women undergoing assisted reproduction.

Women receiving LT4 treatment for SCH should have an empirical dose increase in pregnancy, doubling the dose on 2days per week once pregnancy is confirmed, with regular TSH measurements from 7–9weeks gestation.

There is no benefit from LT4 treatment in improving pregnancy outcomes for euthyroid TPOAb-negative women. Knowing TPOAb status allows for stratification of women who will require thyroid function monitoring during pregnancy. The option of performing preconception TPOAb testing for women with infertility or a history of RPL versus routine early pregnancy thyroid function testing alone are both acceptable strategies, until clinical and cost-effectiveness analyses are available. Further studies are required to determine the role of selenium or steroids in improving pregnancy outcomes for euthyroid TPOAb-positive women.

Limitations, reasons for caution

The evidence for treatment of SCH in women with RPL or subfertility is of low quality and therefore must be interpreted with caution.

Wider implications of the findings

SCH and ATD are common conditions and management strategies are widely debated, particularly in women with history of subfertility or recurrent pregnancy loss. Further high quality studies are needed in this area to help strengthen our knowledge on how to manage such patients.

Trial registration number

Not applicable