Levothyroxine before and during pregnancy does not improve the odds of a live birth in women with normal thyroid function and thyroid peroxidase (TPO) antibodies, a study shows.

The TABLET trial, conducted at 49 centres in the UK, was presented at the Endocrine Society’s annual meeting in New Orleans and simultaneously published in the New England Journal of Medicine.

TPO antibodies are present in about 10% of euthyroid women and they have been linked to increased risk of miscarriage and preterm birth.

Two earlier small studies had found “potentially some benefit” of low-dose levothyroxine in reducing the miscarriage rate and improving the live birth rate, said lead author Dr Rima Dhillon-Smith of the University of Birmingham, UK.