Pregnancy outcome of Japanese patients with glucokinase–maturity‐onset diabetes of the young

AIMS/INTRODUCTION: Glucokinase–maturity‐onset diabetes of the young (GCK‐MODY; also known as MODY2) is a benign hyperglycemic condition, which generally does not require medical interventions. The only known exception is increased birthweight and related perinatal complications in unaffected offspring of affected women. As previous data were obtained mostly from white Europeans, the present study analyzed the pregnancy outcomes of Japanese women with GCK‐MODY to better formulate the management plan for this population. MATERIALS AND METHODS: The study participants were 34 GCK‐MODY families whose members were diagnosed at Osaka City General Hospital during 2010–2017. A total of 53 pregnancies (40 from 23 affected women, 13 from 11 unaffected women) were retrospectively analyzed by chart review. RESULTS: Birthweights of unaffected offspring born to affected women were significantly greater as compared with those of affected offspring (P = 0.003). The risk of >4,000 g birthweight (16%), however, was lower as compared with that previously reported for white Europeans, and none of the offspring had complications related to large birthweight. Insulin treatment of the affected women resulted in a significant reduction in the birthweights of unaffected offspring. Perinatal complications including small‐for‐gestational age birthweight were found only in affected offspring born to insulin‐treated women. CONCLUSIONS: In Japanese GCK‐MODY families, unaffected offspring born to affected women were heavier than affected offspring. However, insulin treatment of affected women might not be advisable because of the lower risk of macrosomic birth injury, and an increased risk of perinatal complications in affected offspring.