Outcomes of Pregnancies Affected by Impaired Glucose Tolerance

Objective: Gestational diabetes mellitus (GDM) is associated with an increase in both maternal and neonatal morbidity. There remains uncertainty, however, about the diagnostic criteria for GDM. We compared pregnancy outcomes across three groups of women, with the aim of establishing a threshold for diagnosis of GDM at our institution.

Methods: Women with a glucose tolerance test (GTT) were identified on the hospital's pathology database. Those women with a singleton pregnancy, in whom a GTT had demonstrated a fasting value </=5.5mmol/L, 2-h blood sugar >/=7.8mmol/L and who confined </=34 weeks gestation were eligible for inclusion. Outcomes were collected from the medical records and obstetric database. These women were managed with either diet modification, regular endocrinologist review and standard antenatal care if the GTT met ADA criteria (n=265, TREATED), or standard antenatal care alone if the GTT did not fulfil ADA criteria (n=213, UNTREATED). A third group comprised of women with normal GTT who received identical treatment to the untreated group (n=197, COMPARISON). Statistical analysis was conducted with chi(2) and ANOVA.

Results: In women with untreated GDM, there was significantly more macrosomia, shoulder dystocia, and preeclampsia, compared with the comparison group. These rates were similar between the treated and comparison groups. There were no significant differences in induction of labour, caesarean section rates, or gestational age at delivery between the groups.

Conclusion: Untreated GDM is associated with larger babies and more birth trauma. We recommend the diagnosis of GDM be made with fasting glucose >/=5.5mmol/L and/or 2h >/=7.8mmol/L on 75g GTT.