Months of hard work controlling your blood sugar and now it all comes down to some hours of labor that still needs good glucose control for the baby. If the sugar levels are high in the mom just prior to delivery this gets carried into the baby causing its pancreas to make extra insulin. If the baby is then delivered there is no more sugar coming from the mom so the baby gets a low blood sugar, neonatal hypoglycemia. The normal sugar in a healthy newborn can dip down to 2.2 mmol/L (40mgs/dL) – much lower than adults can tolerate. Babies born to women with diabetes are more likely so have low blood sugars in the first few hours after birth.
Blood glucose metabolism is being pulled and pushed in all directions in those without diabetes making it hard to control for those with diabetes. Hormones that are involved with labor may also have an impact on blood sugar. The uterus has to push the baby out the birth canal and that uses energy. The stress hormones epinephrine are likely high, the mother is often not eating in case a cesarean section is needed. And then when the placenta is delivered suddenly the hormones that were blocking how insulin works are gone and the woman is supersensitive to insulin. Despite these upheavals it is important to control blood sugar during labor.
For women with GDM their body is making some insulin, just not enough, so most of these women can be simply watched during labor with regular testing of blood sugar. Our system is the woman just continues to check her sugar before breakfast and after meals and if eating to take insulin if it has been needed. Once active labor starts we check the blood sugar every one to two hours (if over 5.6 mmol/L (101 mgs/dL)every two hours) and as long as it stays under 6.5 mmol/L (117 mgs/dL) then all is well. Since many of these women are not eating much and their uterus is burning up calories the sugars usually stay just fine.
If the woman was on insulin for her gestational diabetes we generally look at the amount in relation to her weight, if using less than 0.5 units per kg per day we just watch things like for diet controlled people. If she was taking more insulin that the 0.5 units per kg per day then we usually recommend an intravenous infusion of insulin with intravenous sugar so that we can control the glucose and provide calories. Reviewing our data it may be that we could raise this cut off for needing the intravenous protocol to 1.0 units per kg per day.
What is probably important that there is some protocol in place to handle gestational diabetes in labor, one that involves checking the blood sugar to be sure it stays under 7.0 mmoml/L (126 mgs/dL) and plans to deal with it if it should rise higher. Once the baby is delivered the GDM usually goes away, any insulin can be stopped and the mother can enjoy the fruits of her labor. We normally just check the sugar once the next day to confirm all is well, arrange a blood test for diabetes in six weeks but the routine diabetes testing for the mom is now over.