EndocrinologyTier 2Disease (DEADMAN)

Endocrine disorders in pregnancy - diabetes mellitus

Description

Diabetes in pregnancy encompasses gestational diabetes (new-onset glucose intolerance recognised during pregnancy) and pre-existing diabetes (type 1 or type 2 diagnosed before pregnancy) - both requiring tight glycaemic control given the risk of fetal macrosomia, birth complications, and, for pre-existing diabetes specifically, congenital malformation risk if glycaemic control is poor around conception

Gestational diabetes affects a substantial proportion of pregnancies, with diagnostic criteria and screening approach having been meaningfully revised in recent guidance

Pregnancy is inherently insulin-resistant (placental hormones - human placental lactogen and others - antagonise insulin action to preferentially direct glucose to the fetus) - gestational diabetes emerges when maternal beta-cell reserve cannot compensate for this physiological insulin resistance, explaining why it typically manifests and is screened for in the second/third trimester when insulin resistance peaks

2025 ADIPS diagnostic criteria for gestational diabetes use revised fasting, 1-hour, and 2-hour oral glucose tolerance test thresholds that differ materially from the older 2014 criteria - current local guidance should be checked directly given this represents a genuine, clinically significant threshold change (not a minor update) affecting diagnosis rates
Pre-existing diabetes requires pre-conception counselling and optimisation of glycaemic control (aiming for near-normal HbA1c before conception) given the congenital malformation risk correlating with periconceptional glucose control

Gestational diabetes: dietary/lifestyle modification first-line, with insulin (the traditional standard) or, increasingly, metformin as an option when lifestyle measures are inadequate
Pre-existing diabetes: insulin is generally preferred in pregnancy given the most established safety data and dose-titration flexibility, with tight glycaemic targets throughout pregnancy
Postpartum reclassification testing is essential for gestational diabetes, given substantially elevated future type 2 diabetes risk requiring long-term follow-up

Fetal macrosomia and birth trauma risk, congenital malformation risk with pre-existing diabetes (periconceptional control-dependent), postpartum type 2 diabetes risk after gestational diabetes, 2025 ADIPS criteria threshold revision

The 2025 ADIPS gestational diabetes diagnostic criteria differ materially from the older 2014 thresholds across the fasting, 1-hour, and 2-hour oral glucose tolerance test values - this is a genuine, clinically significant change (not incremental), and current local guidance should be verified directly rather than relying on previously memorised threshold values

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