Subclinical hypothyroidism during pregnancy is associated with an increased likelihood of pre-eclampsia, a systematic review shows.

Pregnant women with thyroid-stimulating hormone (TSH) levels on the high or low end of the normal reference range are also at elevated risk of hypertensive disorders of pregnancy, the international researchers say.

The team — including endocrinologist Professor John Walsh from Sir Charles Gairdner Hospital in Perth — say their data highlight the relevance of follow-up thyroid function tests during pregnancy in those treated with levothyroxine to avoid under- or overtreatment.

In a meta-analysis of 19 cohorts, they examined data from nearly 40,000 pregnant women who were classified according to thyroid function status, to determine the link between thyroid dysfunction with the risk of pre-eclampsia and gestational hypertension.