The TABLET trial
The TABLET trial results: the use of Levothyroxine did not reduce the risk of miscarriage in trial participants nor did it result in a higher rate of live births beyond 34 weeks.
The TABLET trial was set up to see whether a drug called Levothyroxine reduces the risk of miscarriage in women who have thyroid antibodies but who are ‘euthyroid’ – that is, their thyroid hormones are in the normal range. After initially recruiting only women with at least one miscarriage and thyroid antibodies, the researchers opened the trial to include women who had a history of infertility.
In discussion of the results, published in the New England Journal of Medicine online*, the authors note:
“In our multicenter, randomized, placebo-controlled trial, the use of levothyroxine, initiated before conception and continued throughout pregnancy, did not result in a higher rate of live births after at least 34 weeks of gestation than placebo among thyroid peroxidase antibody–positive euthyroid women who had a history of miscarriage or infertility. There was also no significant effect on other pregnancy or neonatal outcomes, including rates of miscarriage and preterm birth.”
Lead author Dr. Rima Dhillon-Smith adds more information about the reason for the trial and its results:
Around 10% of women have thyroid antibodies. These are molecules found in the blood which can fight against the thyroid, causing thyroid problems.
Many women who have these antibodies have a normal working thyroid and so will not have any symptoms. Previous studies have shown that women who have thyroid antibodies, even with a normal working thyroid, are at higher risk of having a miscarriage and premature birth. Small studies have suggested that giving a low dose of a medication called levothyroxine might reduce the risk of miscarriage and improve the chance of having a live baby.
The TABLET trial, published in the New England Journal of Medicine*, investigated whether giving levothyroxine to women with a history of miscarriage or subfertility and known to have thyroid antibodies with a normal thyroid function, would improve the chances of having a live birth.
The study found that giving levothyroxine treatment, started before pregnancy and continued throughout pregnancy, did not improve the chances of having a live baby.
Therefore, the authors recommend that levothyroxine treatment is not given to women who have thyroid antibodies and a normal thyroid in pregnancy as it does not improve outcome.
Dr. Rima Dhillon-Smith PhD MRCOG MBChB
Specialist Registrar in Obstetrics and Gynaecology and Academic Clinical Lecturer in Early Pregnancy and Reproductive Medicine, University of Birmingham, Birmingham Womens Hospital
* New England Journal of Medicine, 4 April 2019
About the TABLET trial
We’ve kept information about the trial below for those who would like to know about it.
TABLET was a randomised, double-blind, placebo-controlled trial:
Randomised The women who take part were given either the treatment drug (Levothyroxine) or a placebo – a dummy drug that has no active ingredients. A computer made the selection so it was completely random.
Double-blind The women in the study weren’t told whether they were taking the active medicine or the placebo – and neither were their doctors. So both were blinded to this information.
Placebo-controlled Half the women in the study had the active medicine and half (the controls) had the placebo. The medicine that they received looked exactly the same to them and their doctors, but a completely separate group kept a record of which women had Levothyroxine and which had the placebo.
Who could take part?
The researchers recruited women who:
- were aged 16 – 40
- hoped to conceive in the next year
- had a previous miscarriage or were due to have fertility treatment
- did not have known thyroid disease – and
- were willing to be selected at random to have either the treatment or a placebo, without knowing which they were given.
Where did it take place?
The following hospitals took part in the trial:
- Arrowe Park Hospital, Wirral
- Basildon Hospital
- Birmingham Heartlands Hospital
- Birmingham Women’s Hospital
- Bradford Royal Infirmary
- Burnley General Hospital
- City Hospital, Birmingham
- Colchester Hospital
- Countess of Chester Hospital
- Crosshouse Hospital, Ayrshire
- Cumberland Infirmary
- Derby Hospital
- Derriford Hospital, Plymouth
- Durham Hospital
- Ealing Hospital, London
- Fairfield General, Burnley
- Frimley Park Hospital
- Furness General Hospital, Cumbria
- Guy’s Hospital, London
- James Cook Hospital, Middlesbrough
- Kings College Hospital, London
- Liverpool Women’s Hospital
- New Cross Hospital, Wolverhampton
- Newham University Hospital
- North Manchester General Hospital
- Ormskirk Hospital
- Princess Royal, Telford
- Queen’s Medical Centre, Nottingham
- Rochdale Hospital
- Royal Bolton Hospital
- Royal Bournemouth Hospital
- Royal Cornwall Hospital
- Royal Devon and Exeter Hospital
- Royal London Hospital
- Royal Oldham Hospital
- Royal Shrewsbury Hospital
- Royal United Hospital, Bath
- Royal Victoria, Newcastle-upon-Tyne
- St Bartholomew’s Hospital
- St James’s Hospital, Leeds
- St Mary’s Hospital, Manchester
- St Mary’s Hospital, London
- St Michael’s Hospital, Bristol
- St Peter’s Hospital, Chertsey
- St Thomas’s Hospital, London
- University College Hospital, London
- University Coventry and Warwickshire Hospitals
- Warrington Hospital
- Watford General Hospital
- Whipps Cross Hospital
- Wrightington Hospital
If you would like more information, please contact the TABLET office at tablet-trial@trials.bham.ac.uk.
If your questions are less medical/scientific and more about feelings or concerns, do contact us at info@miscarriageassociation.org.uk or call us on 01924 200799.