Diabetic complications during pregnancy
Pregnancy places special demands on carbohydrate metabolism and causes the insulin requirement to increase, even in a healthy woman. Consequently, pregnancy may lead to a prediabetic state, to the conversion of an asymptomatic subclinical diabetic state to a clinical one (gestational diabetes occurs in about 1% to 2% of all pregnancies), or to complications in a previously stable diabetic state.
Prevalence of diabetes mellitus increases with age. Maternal and fetal prognoses can be equivalent to those in nondiabetic women if maternal blood glucose is well controlled and ketosis and other complications are prevented. Infant morbidity and mortality depend on recognizing and successfully controlling hypoglycemia, which may develop within hours after delivery.
Causes
In diabetes mellitus, glucose is inadequately used either because insulin isn’t synthesized (as in type 1, insulin-dependent diabetes) or because tissues are resistant to the hormonal action of endogenous insulin (as in type 2, non–insulin-dependent diabetes).
Protective mechanisms
During pregnancy, the fetus relies on maternal glucose as a primary fuel source. Pregnancy triggers protective mechanisms that have anti-insulin effects: increased hormone production (placental lactogen, estrogen, and progesterone), which antagonizes the effects of insulin; degradation of insulin by the placenta; and prolonged elevation of stress hormones (cortisol, epinephrine, and glucagon), which raise blood glucose levels.
In a normal pregnancy, an increase in anti-insulin factors is counterbalanced by an increase in insulin production to maintain normal blood glucose levels. However, women who are prediabetic or diabetic can’t produce sufficient insulin to overcome the insulin antagonist mechanisms of pregnancy, or their tissues are insulin-resistant.
As insulin requirements rise toward term, the patient who is prediabetic may develop gestational diabetes, necessitating dietary management and, possibly, exogenous insulin to achieve glycemic control. The insulin-dependent patient may need increased insulin dosage.
