Gestational diabetes and the risk of late stillbirth: a case–control study from England, UK

Objective To explore the separate effects of being ‘at risk’ of gestational diabetes mellitus ( GDM ) and screening for GDM , and of raised fasting plasma glucose ( FPG ) and clinical diagnosis of GDM , on the risk of late stillbirth. Design Prospective case–control study. Setting Forty‐one maternity units in the UK. Population Women who had a stillbirth ≥28 weeks of gestation ( n = 291) and women with an ongoing pregnancy at the time of interview ( n = 733). Methods Causal mediation analysis explored the joint effects of (i) ‘at risk’ of GDM and screening for GDM and (ii) raised FPG (≥5.6 mmol/l) and clinical diagnosis of GDM on the risks of late stillbirth. Adjusted odds ratios ( aOR ) were estimated by logistic regression adjusted for confounders identified by directed acyclic graphs. Main outcome measures Screening for GDM and FPG levels Results Women ‘at risk’ of GDM , but not screened, experienced 44% greater risk of late stillbirth than those not ‘at risk’ ( aOR 1.44, 95% CI 1.01–2.06). Women ‘at risk’ of GDM who were screened experienced no such increase ( aOR 0.98, 95% CI 0.70–1.36). Women with raised FPG not diagnosed with GDM experienced four‐fold greater risk of late stillbirth than women with normal FPG ( aOR 4.22, 95% CI 1.04–17.02). Women with raised FPG who were diagnosed with GDM experienced no such increase ( aOR 1.10, 95% CI 0.31–3.91). Conclusions Optimal screening and diagnosis of GDM mitigate the higher risks of late stillbirth in women ‘at risk’ of GDM and/or with raised FPG . Failure to diagnose GDM leaves women with raised FPG exposed to avoidable risk of late stillbirth. Tweetable abstract Risk of #stillbirth in gestational diabetes is mitigated by effective screening and diagnosis.