Falling Insulin Requirements and Adverse Pregnancy Outcomes in Women With Pre-pregnancy Diabetes [10D]

INTRODUCTION: A subset of women with pre-gestational diabetes experience a third-trimester fall in insulin requirements (IR). There is no consensus on whether this fall represents placental dysfunction or is a variant of normal third-trimester physiology. Our study sought to determine whether a third-trimester drop in IR is associated with adverse pregnancy outcomes. METHODS: This is a retrospective cohort study of women with type 1 and 2 diabetes. We compared outcomes in those with and without a ≥15% drop in basal IR. The primary outcome was a composite of stillbirth, spontaneous preterm birth, preterm premature rupture of membranes and iatrogenic preterm birth or emergency caesarean delivery for fetal wellbeing concerns. The results were adjusted for the effect of maternal BMI, presence of microvascular disease, and pre-pregnancy hemoglobin A1c >7. The study was approved by the research ethics board at Mount Sinai Hospital. RESULTS: We included 350 women (146 type 1, 204 type 2), of which 15% had a drop of ≥15% in third-trimester basal insulin requirements. There was no difference in the primary outcome between groups (aOR 0.75 [0.27, 1.81]). In isolation the sensitivity and specificity of a ≥15% drop in basal IR as a diagnostic test for the primary outcome was 13% and 85%, respectively. CONCLUSION: A ≥15% drop in third-trimester basal IR is not associated with and is a poor predictor of adverse pregnancy outcomes in women with pre-pregnancy diabetes. It should not be used in isolation as a sole indication for delivery.