Masked hypoglycemia in pregnancy.

Background and objective Hypoglycemia is a major hindrance for optimal glycemic control in women with gestational diabetes mellitus[GDM] on insulin. We objectively estimated masked hypoglycemia [glucose < 2.77mmol/L for ≥30minutes] in pregnant women using a continuous glucose monitoring system[CGMS]. Methods Twenty pregnant women with GDM on insulin [cases] and ten age-matched euglycemic pregnant women [controls] between 24-36 weeks of gestation were recruited. Both groups self monitored their blood glucose(SMBG), and underwent continuous glucose monitoring[CGM] for 72 hours to assess masked hypoglycemia. The masked hypoglycemic episodes were further stratified into two groups (interstitial glucose 2.28-2.77mmol/L and ≤2.22mmol/L). Results Masked hypoglycemia was recorded in 35%(7/20) of cases and 40%(4/10) of controls using CGM, with an average of 1.28 and 1.25 episodes per subject, respectively. The time spent at glucose levels between 2.28-2.77 mmol/L did not differ between the two groups (mean 114 vs. 90 minutes,P = 0.617); but cases spent a longer duration with glucose ≤2.2mmol/L. Babies born to women with GDM were significantly lighter to controls (2860 gram vs. 3290 gram,P = 0.012). There was no significant difference in birth weight within the groups among babies born to women with /or without hypoglycemia. Conclusion Euglycemic pregnant women as well as those with GDM on insulin had masked hypoglycemia. Masked hypoglycemia was not associated with adverse maternal or fetal outcomes. Therefore, low glucose levels in the hypoglycemic range may represent a physiologic adaptation in pregnancy. This response is exaggerated in women with GDM on insulin.