Women with an HbA1c of 41-49 mmol/mol (5.9-6.6%): a higher risk subgroup that may benefit from early pregnancy intervention

Abstract

Aims: To examine whether women with an HbA1c of 41-49 mmol/mol (5.9-6.6%) at diagnosis of gestational diabetes are higher risk than women with an HbA1c of < 41 mmol/mol (5.9%) and whether pregnancy outcomes are improved if treated at < 24 weeks' gestation.

Methods: This was an observational study of women with gestational diabetes diagnosed by early HbA1c screening or subsequent oral glucose tolerance test at < 34 weeks' gestation who delivered at National Women's Health, Auckland, from July 2012 to June 2014. Data were extracted from the hospital database. Women with HbA1c 41-49 mmol/mol (5.9-6.6%) were divided into those seen < 24 weeks (Early, n = 134) and those seen ≥ 24 weeks (Later, n = 151). Those with HbA1c < 41 mmol/mol (5.9%) were labelled Other GDM (n = 661).

Results: The Early and Later groups, compared with Other GDM, had more Polynesian and fewer (non-Indian) Asian women, higher BMI and more required medication (P < 0.001). More were smokers (P = 0.007, 0.02) and more had chronic hypertension (P < 0.001, 0.02). There were higher rates of adverse outcomes in the Later group than the Other GDM group (pre-eclampsia 8.0% vs. 2.4%, P = 0.001, preterm birth 16.6% vs. 8.2%, P = 0.002, neonatal admission 15.5% vs. 9.2%, P = 0.02). Outcomes were similar between the Early group and Other GDM group (pre-eclampsia 1.5% vs. 2.4%, P = 0.5, preterm birth 10.5% vs. 8.2% P = 0.4, neonatal admission 13.6% vs. 9.2%, P = 0.12). Comparing the Early and Later groups, the Early group had less pre-eclampsia, 1.5% vs. 8.0%, adjusted P = 0.03. Other outcomes were not statistically different.

Conclusions: An HbA1c of 41-49 mmol/mol (5.9-6.7%) identifies a higher-risk group of women with gestational diabetes. Overall, our data support early treatment of women with an HbA1c ≥ 41 mmol/mol (5.9%).