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Complications of Pregnancy

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Diabetes Mellitus and Pregnancy

 

Pregestational diabetes mellitus complicates 0.2 percent to 0.5 percent of pregnancies.

Pathophysiology

There is an increased incidence of congenital anomalies and spontaneous abortions in women who are in poor glycemic control during the period of fetal organogenesis, which is nearly complete at seven weeks postconception. Poor glycemic control in pregnant women with diabetes may cause fetal macrosomia (the major manifestation of diabetic fetopathy), which leads to difficult deliveries, an increased need for cesarean delivery, and an increase in fetal morbidity.

Management of pregnancy complicated by diabetes mellitus

First trimester

Routine prenatal laboratory evaluation is performed. In addition to the standard prenatal laboratory panel, tests in diabetic gravida include:

Early morning urine test for microalbuminuria is the earliest clinical sign of diabetic nephropathy. A urine albumin concentration is >20 to 30 mg/L indicates microalbuminuria. Glycosylated hemoglobin concentration is obtained.
Thyrotropin (TSH) and free thyroxine should be measured.
Baseline electrocardiogram should be obtained if not performed within the preceding year.
Dilated and comprehensive eye examination by an ophthalmologist should be performed during the first trimester, then at least every three months until parturition.

Frequency of Testing During Pregnancy in Women with Type I Diabetes

Test Frequency
Hemoglobin A1c Every 4-6 weeks
Blood glucose. Home measurements 4-8 times daily; during weekly/biweekly visits in physician’s office.
Urine ketones During period of illness; when any blood glucose value is >200 mg/dL
Serum creatinine Each trimester.
Urinalysis Weekly/biweekly office visits.
Thyroid function tests Baseline measurements of serumfree T4 and TSH.
Eye examination Baseline and then every 3 months

Women who are in very poor metabolic control after the first visit may require admission to the hospital. Admission is also required for diabetic ketoacidosis.

Glucose monitoring.

Measurements of blood glucose in women with type 1 diabetes should occur at 7:30 AM, 10 AM, 1 PM, 4:30 PM, and 6:30 PM. If the first morning blood glucose value is high, testing should also be performed at bedtime and in middle of the night. Bedtime and middle-of-the-night tests are important to discover, treat, and prevent nocturnal hypoglycemia. Urinary ketones should be measured periodically, especially when the woman is ill or when any blood glucose value is over 200 mg/dL.

Target blood glucose values in pregnant diabetic woman:

A fasting capillary blood glucose concentration of 55 to 65 mg/dL. One-hour postprandial blood glucose concentration less than 120 mg/dL.

Diet recommendations

Approximately 30 kcal/kg per day if the woman is at ideal body weight.
24 kcal/kg per day if 20 to 50 percent above ideal body weight.
12 to 18 kcal/kg per day if more than 50 percent above ideal body weight.
36 to 40 kcal/day if more than 10 percent below ideal body weight.
The recommended distribution of calories is 40 to 50 percent carbohydrate, 20 percent protein, and 30 to 40 percent fat.
Three meals and three snacks per day are recommended. An acceptable calorie distribution would be 10 percent of calories at breakfast, 30 percent at both lunch and dinner, and 30 percent as snacks. A daily supplement of ferrous sulfate (30 mg) and folate (400 μg) is also recommended.

Insulin regimen. Most women with type 1 diabetes require at least three injections of insulin per day.

The average insulin requirement in pregnant women with type 1 diabetes is 0.7 units/kg in the first trimester, often increasing to 0.8 U/kg for weeks 18 to 26, 0.9 U/kg for weeks 27 to 36, and 1.0 U/kg for weeks 37 to term.
Women with type 2 diabetes also should be treated with insulin for blood glucose control, preferably started during the preconception period. During the first trimester, insulin requirements are similar in women with type 1 and type 2 diabetes. However, as the pregnancy proceeds into the third trimester, insulin requirements increase proportionately more in women with type 2 than type 1 diabetes; in one study, for example, the respective insulin doses are 1.6 and 1.2 U/kg per day.

Administer a combination of regular insulin and intermediate-acting insulin (such as NPH insulin). The insulin is initially distributed as follows:

* Approximately 45 percent of the total daily dose is given as NPH insulin and 22 percent as regular insulin before breakfast.
* Approximately 17 percent of the total daily dose is given as both NPH and regular insulin before dinner.
* The premeal dose of regular insulin (including lunch) is given on a sliding scale according to the blood glucose value.

Insulin Adjustment Based upon Self-Measured Blood Glucose (BG) Concentrations

Time Insulin dose being analyzed Adjustment recommendations
7:30AM Bedtime NPH If BG is >90 mg/dL, check at bedtime and 3:00 AM BG.If bedtime value is high, increase dinner regular
10 AM Morning regular insulin If 1 hour postprandial value is above 140 mg/dL, increase next morning regular insulin by 2 units. If the value is <110 mg/dL, decrease next morning AM regular by 2 units.
1 PM Morning NPH insulin If 1 hour postprandial value is above 140 mg/dL, increase next day’s lunch regular insulin by 2 units. If the value is below 110 mg/dL, decrease next day’s lunch regular insulin by 2 units.
4:30 PM Morning NPH insulin If BG is above 90 mg/dL, then increase morning NPH insulin by 2 units. If BG is below 60 mg/dL, then decrease morning NPH by 2 units.
6:30 PM Dinner regular insulin If 1 hour postprandial value is above 140 mg/dL, increase dinner regular insulin by 2 units. If 1 hour value is below 110 mg/dL, decrease dinner regular insulin by 2 units.

Second prenatal visit is scheduled one week after the first. Self-monitored blood glucose values and results from the ophthalmologic and laboratory examination are reviewed.

Second trimester
After the first two prenatal visits, which are scheduled one week apart, women are seen every two to four weeks through the second trimester, or more frequently if glycemic control is suboptimal.

Maternal analyte screening.
A triple or quadruple maternal serum screen should be offered to help detect neural tube defects and Down syndrome (ie, triple screen = alphafetoprotein + unconjugated estriol + human chorionic gonadotropin; inhibin A is added for a quadruple screen).

Ultrasound examination at eighteen weeks of gestation is routine in pregestational diabetes. The ultrasound examination should include a fetal survey with a four-chamber view of the heart and visualization of the outflow tracts

Third trimester
Diabetic gravida should be seen every one to two weeks until 32 weeks of gestation and then weekly until delivery.

Antepartum fetal testing is recommended for pregnancies complicated by pregestational diabetes starting with weekly NSTs at 32 weeks when there is suboptimal glycemic control (hemoglobin A1c values >7 percent) and by 35 weeks with good control (hemoglobin A1c <7 percent), increasing the frequency of testing to two times per week as indicated. In complicated patients with intrauterine growth restriction , oligohydramnios, preeclampsia, or poorly controlled blood sugars, testing may start at 26 weeks.

Assessment of fetal growth.
The ultrasound examination is repeated at 28 to 30 weeks. If there is evidence of intrauterine growth restriction, tests of fetal well-being are initiated. The last sonographic examination is performed at 38 weeks to estimate fetal weight.

Labor and Delivery

Timing of delivery.
There is little benefit in continuing pregnancy beyond 39 weeks if the cervix is favorable. Induction can be safely delayed until 40 weeks in women with excellent glycemic control, no vascular disease or preeclampsia, normal fetal growth, and no history of stillbirth. Prophylactic cesarean delivery may be considered to prevent brachial plexus injury when the estimated fetal weight is greater than 4500 g. Insulin can be given subcutaneously or by intravenous infusion with a goal of maintaining blood glucose concentrations between 70 and 90 mg/dL. Insulin infusion consists of intravenous administration of 15 units of regular insulin in 150 mL of normal saline at a rate of one to three units per hour.

Normal saline may be sufficient to maintain euglycemia when labor is anticipated.
As the mother enters active labor, insulin resistance rapidly decreases and insulin requirements fall rapidly. Thus, continuing insulin therapy is likely to lead to hypoglycemia. To prevent this, glucose should be infused at a rate of 2.5 mg/kg per min. Capillary blood glucose should be measured hourly. The glucose infusion should be doubled for the next hour if the blood glucose value is less than 60 mg/dL. On the other hand, values of 120 mg/dL or more require the administration of regular insulin subcutaneously or intravenously until the blood glucose value falls to 70 to 90 mg/dL. At this time, the insulin dose is titrated to maintain normoglycemia while glucose is infused at a rate of 2.5 mg/kg per min.

If a cesarean delivery is planned, the bedtime NPH insulin dose may be given on the morning of surgery and every eight hours thereafter if surgery is delayed. Insulin requirements drop sharply after delivery. The new mother may not require insulin for 24 to 72 hours. Insulin requirements should be recalculated at this time at 0.6 units/kg per day based upon postpartum weight. Postpartum calorie requirements are 25 kcal/kg per day, and somewhat higher (27 kcal/kg per day) in lactating women. Women in whom labor is induced should receive either no morning insulin or only a small dose of an intermediate-acting insulin. Blood glucose monitoring and glucose and insulin infusion are managed as described above for active labor.

Postpartum.
Insulin requirements drop sharply after delivery; as a result, the new mother may not require insulin for 24 to 72 hours. Insulin requirements should be recalculated at this time at 0.6 units/kg per day based upon postpartum weight and serial blood glucose determinations.

 


 
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