Hypoglycaemia following the 2-hour 75g OGTT in pregnancy - Investigating maternal and foetal outcomes

Abstract

Aims: To investigate differences in maternal and foetal outcomes in pregnancy, where patients developed hypoglycaemia following the 2-hour 75g oral glucose tolerance test (OGTT).

Method: A retrospective cohort study of 200 pregnancies attending the Antenatal Clinic at Tameside General Hospital between 2018 and 2022. Outcomes were compared between 4 groups: normal OGTT [G1; (n = 39, 20%), diagnosis of gestational diabetes mellitus (GDM) based on OGTT [G2; BG ≥ 5.6 mmol/L or 2-h OGTT ≥7.8 (n = 41, 21%)], hypoglycaemia [G3; 2 h OGTT 3.0-3.9 mmol/L (n = 93, 47%)], or clinically significant hypoglycaemia [G4; 2 h OGTT <3.0 mmol/L (n = 27, 14%)]. Maternal BMI, foetal birth weight (FBW), neonatal complications, neo-natal intensive care unit (NICU) stay and conversion to GDM were assessed.

Results: Maternal BMI was lower in G3 and G4 (27.3 kg/m² and 28.1 kg/m² respectively) compared to G1 (30.4 kg/m²) (p = 0.02). NICU stay was more frequent in G3 (12%, n = 11) and G4 (8%, n = 2) compared to G1 (5%, n = 2). Foetal complications occurred in 27% of G3 (n = 25) and 33% of G4 (n = 9) compared to 23% in G1 (n = 9) and 17% in G2 (n = 7). FBW was similar in G1 when compared to G3 and G4 (p = 0.34). Of the 120 patients in G3 and G4, 25 patients self-monitored blood glucose for two weeks; 28% (n = 7) subsequently developed GDM.

Conclusion: Higher rates of NICU stay and foetal complications were seen in both hypoglycaemic groups. In patients with hypoglycaemia following OGTT there is evidence to support self-monitoring blood glucose as 28% were later diagnosed with GDM.

Keywords: Gestational diabetes mellitus; Hypoglycaemia; Oral glucose tolerance test; Pregnancy.