Use of metformin and insulin among pregnant women with gestation diabetes in the United Kingdom: A population‐based cohort study

Aims The contemporary prescription patterns of antidiabetic drugs following guideline changes recommending metformin as first‐line gestational diabetes (GDM) pharmacotherapy is underexplored. We aimed to examined use of metformin and insulin during pregnancy among women with GDM over 20 years in the United Kingdom. Methods We conducted a population‐based cohort study using linked data from the Clinical Practice Research Datalink, its pregnancy register and Hospital Episode Statistics from 1998 to 2017. We included pregnancies of women without prior diabetes history who received GDM diagnosis or initiated an antidiabetic drug after 20 weeks gestation. Patient‐level and practice‐level characteristics were compared between metformin initiators and insulin initiators. We described trends of initiating metformin as first‐line treatment and described time to initiation of rescue insulin overall, and by body mass index among metformin initiators. Results Our cohort included 5633 pregnancies from 5393 women with GDM, of whom 38.9% initiated pharmacotherapy (41% insulin, 59% metformin). Metformin prescriptions (as opposed to insulin) increased substantially, from