Effect of maternal hypoglycemia on the fetus

Severe hypoglycemia (lost of consciousness or convulsion) has been reported in up to 40% of pregnancies complicated by Type 1 diabetes and in up to 22% of cases there is more than one episode reported during pregnancy. Most of these episodes of severe hypoglycemia occur in the first half of the pregnancy, the most critical time for organogenesis. There is no available evidence linking effects of embryopathy in mothers who have suffered hypoglycemia during pregnancy. However, in animal studies, the potential teratogenic effect of maternal hypoglycemia was observed. Fetal weight may be influenced by repetitive events of maternal hypoglycemia, since in different studies newborns with macrosomia were observed, as well as small for gestational age. The macrosomia observed in relation to these events could be explained by hyperglycemia reactive to hypoglycemia, considering that the average Hb1c of these patients was 5.6%. It is infrequent to observe permanent damage to the central nervous system after episodes of severe maternal hypoglycemia, but repetitive episodes would be related to nerological dysfunction of their children. Children exposed to maternal hypoglycemia can develop impairments in cognitive function and are at increased risk for epilepsy. Glucose plays an important role by providing the substrate to produce the energy required in the synaptic transport of neurotransmitters. Since glucose is not stored in the brain, any interruption in supply would interfere with the normal chemical signaling by neurotransmitters between the brain cells. Although the developing brain of a fetus or a child may be more flexible in use of nonglucose fuels (lactate or ketones bodies) for energy, it could also be more prone to permanent alteration of processes in neurosignaling. Most studies show that there are no changes in heart rate or fetal movements during events of moderate maternal hypoglycemia. These findings suggest that the fetus is able to use alternative energy sources (ketones, lactic acid) during these episodes.