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.
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).
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.
Signs and symptoms
All women should receive diagnostic screening for maternal diabetes mellitus during pregnancy. Women at higher risk or with a history of gestational diabetes, fetal or birth problems, may warrant early screening in the second trimester using a formal glucose tolerance test.
Uncontrolled diabetes in a pregnant woman can cause stillbirth, fetal anomalies, premature delivery, and birth of an infant who is large or small for gestational age. Such infants are predisposed to severe episodes of hypoglycemia shortly after birth. These infants may also develop hypocalcemia, hyperbilirubinemia, and respiratory distress syndrome.
The prevalence of gestational diabetes makes careful screening for hyperglycemia appropriate in all pregnancies in each trimester. Abnormal fasting or postprandial blood glucose levels and clinical signs and history suggest diabetes in patients not previously diabetic. A 3-hour glucose tolerance test confirms diabetes mellitus when two or more values are above normal.
Diagnosis of fetal status
Procedures to assess fetal status include stress and nonstress tests, ultrasonography to determine fetal age and growth, measurement of urinary or serum estriols and of phosphatidylglycerol and determination of the lecithin-sphingomyelin ratio from amniotic fluid to predict pulmonary maturity.
Both the newly diagnosed and the established diabetic need dietary management and insulin administration to maintain blood glucose levels within acceptable limits. Most women with overt diabetes mellitus require hospitalization at the beginning of pregnancy to assess physical status, check for cardiac and renal disease, and regulate diabetes.
For pregnant patients with diabetes, therapy includes:
frequent visits to the obstetrician and the internist during the first 6 months of pregnancy; weekly visits may be necessary during the third trimester, an internist may be consulted as necessary.
maintenance of blood glucose levels at or below 95 mg/dl during the third trimester
frequent monitoring for glycosuria and ketonuria (Ketosis presents a grave threat to the fetal central nervous system.)
a high-protein diet of 2 g/day/kg of body weight (a minimum of 80 g/day during the second half of pregnancy), a daily calorie intake of 30 to 40 calories/kg of body weight, a daily carbohydrate intake of 200 g, and enough fat to provide 36% of total calories (However, vigorous calorie restriction can cause starvation ketosis.)
exogenous insulin if diet doesn’t control blood glucose levels. Oral antidiabetic agents are generally contraindicated during pregnancy because they may cause fetal hypoglycemia and congenital anomalies.
Generally, the optimal time for delivery is no different from a normal pregnancy, as long as blood sugars are controlled and no fetal compromise is present.
Depending on fetal status and maternal history, labor may be spontaneous induced or a cesarean section performed. During labor and delivery, the patient with diabetes should receive a continuous I.V. infusion of dextrose with regular insulin in water. Maternal and fetal status must be monitored closely throughout labor.
The patient may benefit from half her prepregnancy dosage of insulin before a cesarean delivery. Her insulin requirement will fall markedly after delivery.
VN:F [1.9.20_1166]Diabetic complications during pregnancy,