Falling Insulin Requirement in Pregnant Women With Diabetes Delivering Preterm: Prevalence, Predictors, and Consequences

Abstract

Context Falling insulin requirement often leads to considerations of whether the pregnancy can continue safely or if delivery is indicated. Objective To evaluate prevalence and predictors of falling insulin requirement in pregnant women with pre-existing diabetes delivering preterm and explore the relationship to fetal asphyxia and neonatal morbidity. Methods Prospective cohort study of 101 consecutive singleton pregnant women with pre-existing diabetes delivering preterm <37 weeks (68 type 1 and 33 type 2 diabetes) where the prevalence of falling insulin requirement (≥20%) before delivery was recorded. Results In total, 27% (27/101) experienced falling insulin requirement of median 30% (interquartile range 24-40) before delivery. In all women with type 1 diabetes the prevalence was 37% (25/68) while it was 43% (24/56) in those with indicated preterm delivery and 6% (2/33) among women with type 2 diabetes. In women with type 1 diabetes and indicated preterm delivery, falling insulin requirement was first identified at 34 +5 (33 +6-35 +4) weeks +days and delivery occurred 3 (1-9) days later. Gestational age at delivery, prevalence of suspected fetal asphyxia and neonatal morbidity were similar in women with and without falling insulin requirement. Neither glycemic control, nausea, or preeclampsia were associated with falling insulin requirement. Conclusion Falling insulin requirement often preceded preterm delivery in women with type 1 diabetes, foremost when preterm delivery was indicated, but was not related to fetal asphyxia or neonatal morbidity. Whether falling insulin requirement in late pregnancy is a warning sign of placental insufficiency or mainly reflects variations in normal physiology needs further investigation.