Gestational hypothyroidism: development of mild hypothyroidism in early pregnancy in previously euthyroid women.

Objective: To determine the proportion of euthyroid women attending a fertility practice who develop hypothyroidism in very early pregnancy (gestational hypothyroidism [GHT]), and to examine the association of GHT with exogenous gonadotropin treatment.

Design: Retrospective cohort study.

Setting: A private reproductive medicine practice.