Maternal diabetes affects >8% of the 4 million live births annually in the United States.1 Three fourths of pregnant patients with diabetes have either gestational diabetes or type 2 diabetes diagnosed through prenatal screening. Of the remaining 25%, 1% have preexisting type 1 diabetes, and the remaining are type 2 diabetics. Pregnant diabetic women are at increased risk for spontaneous abortion, particularly patients with poor glycemic control early in pregnancy, preexisting vascular disease, and pre-eclampsia. Pregnant diabetics are also at increased risk for several pregnancy complications, including pregnancy-induced hypertension, preterm labor, spontaneous abortion, pyelonephritis, and diabetic ketoacidosis (DKA). The goal of treatment during pregnancy is to prevent spontaneous abortions, hyperglycemia-induced congenital abnormalities and ketoacidosis, and hypoglycemia.
Oral hypoglycemic agents, such as metformin and glyburide, are occasionally used in select patients with gestational diabetes.2 A significant portion of gestational diabetics can be managed with diet alone if they can maintain glycemic goals with frequent glucose monitoring.
The American College of Obstetricians and Gynecologists recommends the following goals for maintaining euglycemia in pregnant diabetic patients: a fasting blood glucose concentration of ≤95 milligrams/dL and a 2-hour postprandial glucose concentration ≤120 milligrams/dL.3 Patients with gestational diabetes who are managed by diet alone rarely develop acute hyperglycemic complications because glucose values rarely reach levels consistent with DKA. Among patients with preexisting type 1 and type 2 diabetes, the need for insulin increases throughout the course of pregnancy. Historically, all type 2 diabetics were switched to insulin as soon as possible (even prior to conception) to ensure appropriate glycemic control and due to concerns over the safety of oral hypoglycemic agents in pregnancy. Recent studies in gestational diabetes have not shown metformin or glyburide to have any harmful fetal effects, but long-term studies are needed. Although metformin may be continued in select patients, there is no consensus on the use of these oral agents alone in the pregnant patient with type 2 diabetes.2,3,4,5
In general, during the first trimester, the initial insulin requirement is 0.7 units/kg/day. By late pregnancy, patients generally require 1 unit/kg/day.6
Neutral protamine Hagedorn (NPH)/regular insulin combinations are still first-line insulin therapy, but the long-acting analog insulin detemir (Levemir) is approved by the U.S. Food and Drug Administration for use in pregnancy and is category B. Compared to NPH, insulin detemir improves fasting plasma glucose and decreases hypoglycemic events. There is a strong evidence base to recommend insulin detemir in pregnancy, but the lack of definitive fetal benefit means that there is no pressing need to switch a woman whose diabetes is well controlled by NPH insulin to insulin detemir.
Insulin glargine (Lantus) is still category C. It is generally not initiated during pregnancy. However, it seems reasonable to continue insulin glargine when it was successful maintaining excellent glycemic control in a woman who is now pregnant.7
Women with type 1 diabetes have three to five times more hypoglycemic episodes than the period prior to pregnancy.8 Risk factors for severe hypoglycemia during pregnancy include a history of severe hypoglycemia in the year preceding pregnancy, impaired hypoglycemia awareness, long duration of diabetes, low HbA1c in early pregnancy, fluctuating plasma glucose levels, and excessive use of insulin injections between meals.8 Hypoglycemia generally presents as sweating, tremors, blurred or double vision, weakness, hunger, confusion, paraesthesias, anxiety, palpitations, nausea, headache, or stupor. Moderate and infrequent hypoglycemic episodes are generally well tolerated by the fetus.4 Pregnant diabetic women should be educated about the symptoms and treatment of hypoglycemia. Treat mild hypoglycemia (i.e., a glucose level of <70 milligrams/dL in patients who are able to follow commands) by giving juice, glucose, or food by mouth. Provide standard treatment for more severe hypoglycemia, with IV glucose or PO glucose or glucagon 1 to 2 milligrams SC or IV (see chapters 223, "Type 1 Diabetes Mellitus" and 224, "Type 2 Diabetes Mellitus").
DIABETIC KETOACIDOSIS IN PREGNANCY
A pregnant diabetic who is ill appearing, has persistent nausea and vomiting, and/or has a blood glucose level ≥180 milligrams/dL should be screened for DKA with serum or urine ketones and a serum chemistry panel. Management guidelines for pregnant women with DKA are the same as for nonpregnant patients9 (see chapter 225, "Diabetic Ketoacidosis"). In addition to the usual care, obtain fetal heart tones, administer oxygen, and for third-trimester patients, place in the left lateral decubitus position to displace the uterus and improve uterine blood flow. Most fetal heart rate abnormalities subside after correction of maternal hypovolemia and acidosis. Consult with the patient's physician, and admit the patient to the hospital.
The incidence of DKA in pregnancy decreases with early diagnosis of insulin-dependent diabetes, improved prenatal counseling, and care with an identifiable primary care provider.10,11 DKA most commonly affects women in the second or third trimester or pregnant women with new-onset type 1 diabetes.10,12
Women who use continuous SC insulin infusions (the insulin pump) can develop DKA whether they are pregnant or not. DKA can develop very quickly and unexpectedly, especially in patients who have recently started using the pump.13,14 Use of continuous insulin pumps during pregnancy is equivalent, but not superior, to scheduled injections. Management of DKA in a pregnant woman with an insulin pump is the same as the nonpregnant patient.
DKA is not an indication for delivery. Although fetal heart rate monitoring in maternal DKA may initially demonstrate a nonreassuring pattern, patterns usually improve as maternal ketoacidosis is corrected, and mother will tolerate delivery or cesarean section better once acidosis resolves.10,15