Deceptive Late Maternal Euglycaemia

Background: Strict glycemic control is the most critical factor determining outcome in Gestational Diabetes mellitus. But having capillary blood glucose readings within the target levels, in the late trimester may be deceptive. If fetal hyperinsulinaemia and fetopathy have already set in, maternal glucose may be spuriously normal. We support this hypothesis based on our experience with 4 GDM patients who apparently reported normal blood glucose in late trimester, yet ended up with neonatal complications. Materials and Methods: Records of mothers of four neonates (Infant of diabetic mother) admitted in neonatal ICU with GDM associated complications were retrospectively analyzed. Diagnosis of GDM was made as per the ADA guidelines. The blood glucose values of the 9-point readings (Fasting, pre-lunch, pre-dinner, 1hr and 2hr post breakfast, lunch and dinner) every 3 to 5 days, which the patients shared online were plotted and studied. Mode of delivery and neonatal outcome were noted. Results: All patients (mean age 28.5years, range 24–31) presented to us only in third trimester though two of them had deranged OGTT during first trimester screening elsewhere. The average HbA1c at the time of presentation was 5.425 (Range 4.8 to6.3). Only one of them was on insulin for a short term, which she stopped on her own as the readings continued to be in range even after stopping insulin. Of the 529 last trimester readings shared by the patients, 91.3% were within the target range of FBS< 92mg/dl, 1and 2 post meals <140 and 120 respectively, and pre meals < 95mg/dl. Three of them were induced (Two at 40 weeks and one at 38.4 weeks) for labour. The obstetrical outcomes were as follows: one had LSCS due to non-descent of head, second had vacuum assisted delivery, third had shoulder dystocia and fourth had normal delivery. The neonatal outcomes in respective cases were large for date baby with hypocalcaemia, transient HOCM with hypocalcaemia, shoulder dystocia with perinatal depression, PDA with respiratory distress. Conclusion: GDM should be intervened before the establishment of diabetic fetopathy. Missing the initial spikes in maternal glucose and the consequent surreptitious transfer of glucose to fetus can initiate such fetopathy. There is rerouting or detour of the maternal glucose, to the fetal system, for its disposal. Hence low or normal blood glucose readings in a known GDM patient should alert the clinician about the possibility of fetal glucose steal.(1) Highly suspicious cases can be monitored for polyhydramnios and fetal and maternal weight gain. The best ways to prevent this are pre-conceptional screening for IGT and universal screening for GDM with OGTT in each trimester. Reference: 1. Desoye, Gernot & Nolan, Christopher. (2016). The fetal glucose steal: an underappreciated phenomenon in diabetic pregnancy. Diabetologia. 59. 10.1007/s00125-016-3931-6.aq`