Physiological effects of pregnancy on glucose metabolism

Pregnancy is a diabetogenic state for the following reasons:

• human placental lactogen has anti-insulin and lipolytic effects. It increases the glucose levels in maternal plasma and thus makes more glucose available to the fetus
• steroid hormones have an anti-insulin effect (especially corticosteroids and progesterone)
• some insulin may be destroyed by the placenta

Despite the insulin resistance of pregnancy, hyper- insulinaemia results in fasting levels of blood glucose which are 0.5 mM lower than in non-pregnant women.

Insulin resistance is made evident by the higher peaks of blood glucose following meals.

The diabetogenic effects of pregnancy are increased by:

• maternal obesity
• repeated pregnancy

Glycosuria is more common during pregnancy due to a lowered renal threshold for glucose excretion.