During the latter part of pregnancy, it often becomes more difficult to recognize symptoms of hypoglycaemia as the threshold for developing symptoms will be lowered because of frequent low blood glucose levels. The HbA1c value for women without diabetes is approximately 0.5-1% lower at the end of pregnancy, which is the reason for aiming for an HbA1c close to 6% (the upper limit for individuals without diabetes) during the later part of pregnancy. In a Scottish study, half of the women attained an HbA1c in the non-diabetic range at some point during their pregnancy. Within 1 year, however, most of them increased in HbA1c to levels observed before pregnancy. This may be attributed to not having the time to take care of their diabetes in the most effective way at the same time as caring for an infant at home. Women giving birth to their second or third child had higher HbA1c during pregnancy, suggesting that the amount of work to be done at home affects how easy it is to care for your diabetes during pregnancy.
During pregnancy, the ketone production during periods of insulin deficiency is increased, making ketoacidosis more likely. Ketoacidosis during pregnancy is very dangerous, especially for the unborn child. You should therefore check for ketones in blood or urine regularly, especially if you are being or feeling sick, or have an infection with a raised temperature. A bedtime snack is usually necessary for pregnant women as it decreases the risk of night time hypoglycaemia and fasting ketones. Ketones will show in the urine after only 12-14 hours of fasting. Urine testing every morning will show whether or not you have “starvation ketones” from inadequate carbohydrate intake in the evening. Morning ketones are present in 30% of pregnant women who do not have diabetes. A slight delay in development was found in children aged 2-9 years whose mothers had raised ketone levels during pregnancy.
If you use an insulin pump, your risk of ketoacidosis will increase due to the smaller insulin depot. If the pump infusion set fails during the night you will have high blood glucose levels and elevated levels of ketones in the morning. One method of avoiding this is to give a bedtime injection of intermediate-acting insulin (0.2 U/kg, 0.1U/lb) in addition to the normal basal dose delivered by the pump. The renal threshold is usually lowered in pregnant women, causing an increased excretion of glucose via the urine. Urine tests for glucose cannot be relied upon therefore.