A 5-year South Island observational cohort study of pregnancies complicated by an elevated HbA1c in the prediabetes range 41-47 mmol/mol measured at booking (prior to 24 weeks gestation) — ASN Events
  1. Schedule
  2. Session 1: Antenatal and Technology
  3. A 5-year South Island observational cohort study of pregnancies complicated by an elevated HbA1c in the prediabetes range 41-47 mmol/mol measured at booking (prior to 24 weeks gestation)

A 5-year South Island observational cohort study of pregnancies complicated by an elevated HbA1c in the prediabetes range 41-47 mmol/mol measured at booking (prior to 24 weeks gestation) (#8)

Ruth Hughes 1 2 , Emma Abraham 1
  1. Department of Obstetrics and Gynaecology, University of Otago, Christchurch, New Zealand
  2. Obstetrics and Gynecology , Waitaha Canterbury, Christchurch Women's HospitalTe Whatu Ora, Medical doctor: Specialist, New Zealand

Introduction/aims: Measurement of HbA1c in early pregnancy to screen for pre-existing diabetes is routine across New Zealand.  This screening practice also identifies prediabetes and the best management of these mothers is unclear and differs by centre and the NZ ministry of health gestational diabetes (GDM) guidelines recommend a glucose tolerance test at 24-28 weeks gestation.  We aim to describe antenatal management and postpartum follow-up of pregnancies complicated by prediabetes at booking.  

Methods: A 5-year retrospective observational study of pregnancies complicated by a HbA1c 41-47mmol/mol measured at booking (<24 weeks gestation), by the Southern Community Laboratory that services most of the South Island of NZ. Outcomes were sourced from electronic and paper hospital records. Ethical approval granted by Health and Disability Ethics Committee.

Results: Excluding those with known pre-existing diabetes, 361 pregnancies were included. The mean (SD) age and BMI were 32.5 (6.0) years and 34.3 (8.7) kg/m2.  Ethnicity was Māori 18.3%, Pasifika 14.4%, Indian 16.1%, other Asian 19.4%, European + other 31.9%.

Antenatal care differed by centre.  Of the 259 ongoing pregnancies, 145 (group A) were referred early to a diabetes clinic for self-monitoring of blood glucose and 114 (group B) were offered a further diagnostic test.  In group A, 91% required pharmacotherapy in addition to lifestyle management, 82.7% commencing treatment <24 weeks gestation. In group B, 64% required pharmacotherapy with 26.3% starting <24 weeks gestation.  There were no perinatal deaths in group A and 4 (3.5%) in group B.

Post-partum follow-up ranged from 3 months to 5 years, 78.8% had ≥1 follow-up HbA1c and 80.0% were abnormal.  The cumulative postpartum rate of prediabetes was 44.4%, type 2 diabetes 32.8%, type 1 diabetes 1.1%, and GCK MODY 1.8%.  In contrast, we examined a control group of pregnancies complicated by GDM but with a normal HbA1c at booking (n=359) followed for 5 years postpartum.  5% had no further testing and of the 341 tested, 87.4% were normal, 13.5% had prediabetes, 3.5% had type 2 diabetes and 0.9% had type 1 diabetes.

Discussion/Conclusions: The current NZ MoH GDM guidance delays the opportunity for early intervention in the vulnerable group of mothers with a booking HbA1c 41-47mmol/mol.  In addition to a higher rate of adverse pregnancy outcome compared with the background birthing population, this group have a very high rate of progression to diabetes postpartum. Optimising treatment after the first antenatal HbA1c test could reduce barriers to care and enhance equitable outcomes.  

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