Optimal glycaemic control is of the utmost importance to achieve the best possible outcome of a pregnancy complicated by diabetes. This holds for pregnancies in women with preconceptional type 1 or type 2 diabetes as well as for pregnancies complicated by gestational diabetes. Glycaemic control is conventionally expressed in the HbA1c value but the HbA1c value does not completely capture the complexity of glycaemic control. The daily glucose profile measured by the patients themselves through measurements performed in capillary blood obtained by finger stick provides valuable information needed to adjust insulin therapy. Hypoglycaemia is the major threat to the pregnant woman or the woman with tight glycaemic control in the run-up to pregnancy. Repetitive hypoglycaemia can lead to hypoglycaemia unawareness, which is reversible with prevention of hypoglycaemia. A delicate balance should be struck between preventing hyperglycaemia and hypoglycaemia. Insulin requirements are not uniform across the day: it is low during the night with a more or less pronounced rise at dawn, followed by a gradual decrease during the remainder of the day. A basal amount of insulin is needed to regulate the endogenous glucose production, short-acting insulin shots are needed to handle exogenous glucose loads. Insulin therapy means two choices: the type of insulin used and the method of insulin administration. Regarding the type of insulin, the choice is between human and analogue insulins. The analogue short-acting insulin aspart has been shown to be safe during pregnancy in a randomised trial and has received registration for this indication; the short-acting analogue insulin lispro has been shown to be safe in observational studies. No such information is available on the long-acting insulin analogues detemir and glargine and both are prescribed off-label with human long-acting insulin as obvious alternatives. Randomised trials have not been able to show superiority of continuous subcutaneous insulin administration (CSII (insulin pump)) over intensive insulin injection therapy (multiple-dose insulin (MDI)) on any maternal or foeto-neonatal end point. However, group sizes were far too small to allow assessment of superiority and issues such as manageability of the disease and quality of life were never assessed. These two issues are of major importance to patients. The first trimester is often the period of most hypoglycaemic events, and insulin therapy should be especially closely monitored and adjusted in this period. After midterm, insulin requirements increase. Continuous glucose monitoring can offer better insights into the glycaemic profile than self-monitoring of blood glucose levels by the patients but the place of these new monitoring techniques has yet to be established more clearly. Insulin therapy during labour means short-acting insulin adjusted to achieve glucose levels between 4 and 8 mmol l(-1) to prevent neonatal hypoglycaemia as much as possible. After delivery, glycaemic control must be relaxed to prevent hypoglycaemia, especially in women who breastfeed.
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