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(See also Diabetes Mellitus and Disorders of Carbohydrate Metabolism)
Pregnancy aggravates preexisting type 1 (insulin-dependent) and type 2 (non–insulin-dependent) diabetes but does not appear to exacerbate diabetic retinopathy, nephropathy, or neuropathy.
Gestational diabetes (diabetes that begins during pregnancy) can develop in overweight, hyperinsulinemic, insulin-resistant women or in thin, relatively insulin-deficient women. Gestational diabetes occurs in 1 to 3% of all pregnancies, but the rate may be much higher in certain groups (eg, Mexican Americans, American Indians, Asians, Indians, Pacific Islanders).
Diabetes during pregnancy increases fetal and maternal morbidity and mortality. Neonates are at risk of respiratory distress, hypoglycemia, hypocalcemia, hyperbilirubinemia, polycythemia, and hyperviscosity. Poor control of preexisting or gestational diabetes during organogenesis (up to about 10 wk gestation) increases risk of major congenital malformations and spontaneous abortion. Poor control of diabetes later in pregnancy increases risk of fetal macrosomia (usually defined as fetal weight > 4000 or > 4500 g at birth), preeclampsia, and spontaneous abortion. However, gestational diabetes can result in fetal macrosomia even if blood glucose is kept nearly normal.
Treatment
Preconception counseling and optimal control of diabetes before, during, and after pregnancy minimize maternal and fetal risks, including congenital malformations. Because malformations may develop before pregnancy is diagnosed, the need for constant, strict control of glucose levels is stressed to women who have diabetes and who are considering pregnancy (or who are not using contraception).
Most experts recommend that all pregnant women be screened for gestational diabetes (see Approach to the Pregnant Woman and Prenatal Care: Laboratory testing). A glucose tolerance test is usually recommended, but the diagnosis can probably be made by a fasting plasma glucose of > 126 mg/dL or a random plasma glucose > 200 mg/dL.
To minimize risks, clinicians should do all of the following:
In regional perinatal centers, specialists in management of diabetic complications are available.
During pregnancy
Treatment can vary, but some general management guidelines are useful (see Table 1: Pregnancy Complicated by Disease: Management of Type 1 Diabetes Mellitus* During Pregnancy , Table 2: Pregnancy Complicated by Disease: Management of Type 2 Diabetes Mellitus* During Pregnancy, and Table 3: Pregnancy Complicated by Disease: Management of Gestational Diabetes During Pregnancy). Women with type 1 or 2 should monitor their blood glucose levels at home. During pregnancy, normal fasting blood glucose levels are about 76 mg/dL (4.2 mmol/L); treatment aims to keep fasting blood glucose levels at < 95 mg/dL (< 5.3 mmol/L) and 2-h postprandial levels at ≤ 120 mg/dL (≤ 6.6 mmol/L). The goals are no wide blood glucose fluctuations and glycosylated Hb (Hb A1c) levels kept at < 8%.
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Table 1
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| Management of Type 1 Diabetes Mellitus* During Pregnancy |
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Time Frame
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Measures
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Before conception
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Diabetes is controlled.
Risk is lowest if Hb A1c levels are ≤ 8% at conception.†
Evaluation includes
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24-h urine collection (protein excretion and creatinine clearance) to check for renal complications
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Ophthalmologic examination to check for retinal complications
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ECG to check for cardiac complications
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Prenatal
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Prenatal visits begin as soon as pregnancy is recognized.
Frequency of visits is determined by degree of glycemic control.
Diet should be individualized according to ADA guidelines and coordinated with insulin administration.
Three meals and 3 snacks/day are recommended, with emphasis on consistent timing.
Women are instructed in and should do blood glucose self-monitoring.
Women should be cautioned about the dangers of hypoglycemia during exercise and at night.
Women and their family members should be instructed in glucagon administration.
Hb A1c level should be checked every trimester.
Fetal monitoring with the following should be done weekly from 32 wk to delivery (or earlier if indicated):
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Nonstress tests
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Biophysical profiles
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Kick counts
Amount and type of insulin should be individualized. In the am; two thirds of the total dose (60% NPH, 40% regular) is taken; in the pm; one third (50% NPH, 50% regular) is taken.‡
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During labor and delivery
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Vaginal delivery at term is possible if women have documented dating criteria and good glycemic control.
Amniocentesis is not done unless indicated for another problem or requested by the couple.
Cesarean delivery should be reserved for obstetrical indications or fetal macrosomia (> 4000 or > 4500 g), which increases risk of shoulder dystocia.
Delivery should occur by 38-40 wk.
During delivery, a constant low-dose insulin infusion is usually preferred, and the usual sc administration of insulin is stopped. If induction is planned, the usual pm NPH insulin dose is given on the day before induction.
Postpartum and continuing diabetes care should be arranged.
Postpartum insulin requirements may decrease by up to 50%.
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*Guidelines are only suggested; marked individual variations require appropriate adjustments.
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†Normal values may differ depending on laboratory methods used.
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‡Some hospital programs recommend up to 4 insulin injections daily. Continuous sc insulin infusion, which is labor-intensive, can sometimes be given in specialized diabetic research settings.
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ADA = American Diabetes Association; Hb A1c
= glycosylated Hb; NPH = neutral protamine Hagedorn.
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Table 2
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| Management of Type 2 Diabetes Mellitus* During Pregnancy |
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Time Frame
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Measures
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Before conception
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Hyperglycemia is controlled.
Risk is lowest if Hb A1c levels are ≤ 8% at conception.†
Weight loss is encouraged if BMI is >27 kg/m2.
The diet should be low in fat, relatively high in complex carbohydrates, and high in fiber.
Exercise is encouraged.
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Prenatal
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For overweight women, diet and caloric intake are individualized and monitored to avoid weight gain of > 9 kg; daytime snacks are discouraged.
Moderate walking after meals is recommended.
Women are instructed in and should do blood glucose self-monitoring.
The 2-h postbreakfast blood glucose level is checked weekly at clinic visits.
Hb A1c level should be checked every trimester.
Fetal monitoring with the following should be done weekly from 32 wk to delivery (or earlier if indicated):
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Nonstress tests
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Biophysical profiles
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Kick counts
Amount and type of insulin is individualized. For obese women, regular insulin is taken before each meal. For women who are not obese, two thirds of the total dose (60% NPH, 40% regular) is taken in the am; one third (50% NPH, 50% regular) is taken in the pm.
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During labor and delivery
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Management is the same as for type 1 (see Table 1: Pregnancy Complicated by Disease: Management of Type 1 Diabetes Mellitus* During Pregnancy).
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*Guidelines are only suggested; marked individual variations require appropriate adjustments.
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†Normal values may differ depending on laboratory methods used.
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BMI = body mass index; Hb A1c
= glycosylated Hb; NPH = neutral protamine Hagedorn.
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Table 3
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| Management of Gestational Diabetes During Pregnancy |
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Time Frame
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Measures
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Before conception
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Women who have had gestational diabetes in previous pregnancies should try to reach a normal weight and engage in modest exercise.
The diet should be low in fat, relatively high in complex carbohydrates, and high in fiber.
Fasting plasma glucose and Hb A1c levels should be checked.
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Prenatal
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Diet and caloric intake are individualized and monitored to prevent weight gain of > 9 kg. Obese women are discouraged from daytime snacks.
Moderate exercise after meals is recommended.
Fetal monitoring with the following should be done weekly from 32 wk to delivery (or earlier if indicated):
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Nonstress tests
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Biophysical profiles
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Kick counts
Insulin therapy is reserved for persistent hyperglycemia (fasting plasma glucose > 95 mg/dL or 2-h postprandial plasma glucose > 120 mg/dL) despite a trial of dietary therapy for ≥2 wk.
Amount and type of insulin should be individualized. For obese women, regular insulin is taken before each meal. For women who are not obese, two thirds of the total dose (60% NPH, 40% regular) is taken in the am; one third (50% NPH, 50% regular) is taken in the pm.
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During labor and delivery
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Vaginal delivery at term is possible if women have a well-documented delivery date and good diabetic control.
Amniocentesis may not be required.
Cesarean delivery should be reserved for obstetric indications or fetal macrosomia (> 4000 or > 4500 g), which increases risk of shoulder dystocia.
Delivery should occur by 38-40 wk.
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Hb A1c
= glycosylated Hb; NPH = neutral protamine Hagedorn.
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Insulin is the traditional drug of choice because it cannot cross the placenta and provides more predictable glucose control; it is used for types 1 and 2 diabetes and for some women with gestational diabetes. Human insulin is used if possible because it minimizes antibody formation. Insulin antibodies cross the placenta, but their effect on the fetus is unknown. In some women with long-standing type 1 diabetes, hypoglycemia does not trigger the normal release of counterregulatory hormones (catecholamines, glucagon, cortisol, and growth hormone); thus, too much insulin can trigger hypoglycemic coma without premonitory symptoms. All pregnant women with type 1 should have glucagon kits and be instructed (as should family members) in giving glucagon if severe hypoglycemia (indicated by unconsciousness, confusion, or blood glucose levels < 40 mg/dL [< 2.2 mmol/L]) occurs.
Oral hypoglycemic drugs (eg, glyburide) are being increasingly used to manage diabetes in pregnant women because of the ease of administration (pills compared to injections), low cost, and single daily dosing. Several studies have shown that glyburide is safe during pregnancy and that it provides control equivalent to that of insulin for women with gestational diabetes. For women with type II diabetes before pregnancy, data for use of oral drugs during pregnancy are scant; insulin is most often preferred. Oral hypoglycemics taken during pregnancy may be continued postpartum during breastfeeding, but the infant should be closely monitored for signs of hypoglycemia.
Management of complications
Although diabetic retinopathy, nephropathy, and mild neuropathy are not contraindications to pregnancy, they require preconception counseling and close management before and during pregnancy.
Retinopathy requires that an ophthalmologic examination be done every trimester. If proliferative retinopathy is noted at the first prenatal visit, photocoagulation should be used as soon as possible to prevent progressive deterioration.
Nephropathy, particularly in women with renal transplants, predisposes to pregnancy-induced hypertension. Risk of preterm delivery is higher if maternal renal function is impaired or if transplantation was recent. Prognosis is best if delivery occurs ≥ 2 yr after transplantation.
Congenital malformations of major organs are predicted by elevated Hb A1c levels at conception and during the first 8 wk of pregnancy. If the level is ≥ 8.5% during the 1st trimester, risk of congenital malformations is significantly increased, and targeted ultrasonography and fetal echocardiography are done during the 2nd trimester to check for malformations. If women with type 2 diabetes take oral hypoglycemic drugs during the 1st trimester, fetal risk of congenital malformations is unknown (see Table 2: Drugs in Pregnancy: Some Drugs With Adverse Effects During Pregnancy).
Labor and delivery
Certain precautions are required to ensure an optimal outcome.
Timing of delivery depends on fetal well-being. Women are told to count fetal movements during a 60-min period daily (fetal kick count) and to report any sudden decreases to the obstetrician immediately. Nonstress testing (see Normal Pregnancy, Labor, and Delivery: Fetal Monitoring) is begun at 32 wk and, if results are nonreassuring, is followed by a biophysical profile (measurement of amniotic fluid and fetal muscle tone, movement, and breathing pattern). These tests and similar noninvasive prenatal fetal monitoring tests (called antenatal testing) are initiated earlier if women have severe hypertension or a renal disorder or if fetal growth restriction is suspected. Amniocentesis to assess fetal lung maturity is often necessary for women with the following:
Type of delivery is usually spontaneous vaginal delivery at term. If labor does not begin spontaneously by 38 to 40 wk, induction is necessary because of the increasing risk of stillbirth and shoulder dystocia. Dysfunctional labor, fetopelvic disproportion, or risk of shoulder dystocia may make cesarean delivery necessary.
Blood glucose levels are best controlled during labor and delivery by a continuous low-dose insulin infusion. If induction is planned, women eat their usual diet the day before and take their usual insulin dose. On the morning of labor induction, breakfast and insulin are withheld, baseline fasting plasma glucose is measured, and an IV infusion of 5% dextrose in 0.45% saline solution is started at 125 mL/h, using an infusion pump. Initial insulin infusion rate is determined by capillary glucose level. Insulin dose is determined as followed:
For spontaneous labor, the procedure is the same, except that if intermediate-acting insulin was taken in the previous 12 h, the insulin dose is decreased. For women who have fever, infection, or other complications and for obese women who have type 2 and have required > 100 units of insulin/day before pregnancy, the insulin dose is increased.
Postpartum
After delivery, loss of the placenta, which synthesizes large amounts of insulin antagonist hormones throughout pregnancy, decreases the insulin requirement immediately. Thus, women with gestational diabetes and many of those with type 2 require no insulin postpartum. For women with type 1, insulin requirements decrease dramatically but then gradually increase after about 72 h.
During the first 6 wk postpartum, the goal is tight glucose control. Glucose levels are checked before meals and at bedtime. Breastfeeding is not contraindicated but may result in hypoglycemia if oral hypoglycemics are taken. Women who have had gestational diabetes should have a 2-h oral glucose tolerance test with 75 g of glucose at 6 to 12 wk postpartum to determine whether diabetes has resolved.
Last full review/revision December 2008 by Sean C. Blackwell, MD
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