Diabetes Mellitus in Pregnancy

1. 1. ACOG Practice Bulletin No. 190: Gestational Diabetes Mellitus. Obstet Gynecol 131(2):e49-e64, 2018. doi:10.1097/AOG.0000000000002501

Treatment can vary, but some general management guidelines are useful (see tables Management of Type 1 Diabetes During Pregnancy, Management of Type 2 Diabetes During Pregnancy, and 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).

Goals of treatment are

• Fasting blood glucose levels at < 95 mg/dL (< 5.3 mmol/L)

• 2-hour postprandial levels at ≤ 120 mg/dL (≤ 6.6 mmol/L)

• No wide blood glucose fluctuations

• Glycosylated hemoglobin (HbA1c) levels at < 6.5%

Insulin is the traditional treatment 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. Insulininsulin< 40 mg/dL [< 2.2 mmol/L]) occurs.

Oral hypoglycemic drugsinsulin for women with gestational diabetes. For women with type 2 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.

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 gestational 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 years after transplantation.

Congenital malformations of major organs are predicted by elevated HbA1c levels at conception and during the first 8 weeks 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 (2). If women with type 2 diabetes take oral hypoglycemic drugs during the 1st trimester, fetal risk of congenital malformations is unknown (see table Some Drugs With Adverse Effects During Pregnancy).

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-minute period daily (fetal kick count) and to report any sudden decreases to the obstetrician immediately. Antenatal testing is begun at 32 weeks; it is done earlier if women have severe hypertension or a renal disorder or if fetal growth restriction is suspected. Amniocentesis to assess fetal lung maturity may be necessary for women with the following:

• Obstetric complications in past pregnancies

• Inadequate prenatal care

• Uncertain delivery date

• Poor glucose control

• Poor adherence to therapy

Type of delivery is usually spontaneous vaginal delivery at term. Risk of stillbirth and shoulder dystocia increases near term. Thus, if labor does not begin spontaneously by 39 weeks, induction is often necessary. 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 insulin infusion rate is determined by capillary glucose level. Insulin dose is determined as follows:

• Initially: 0 units for a capillary level of < 80 mg/dL (< 4.4 mmol/L) or 0.5 units/hour for a level of 80 to 100 mg/dL (4.4 to 5.5 mmol/L)

• Thereafter: Increased by 0.5 units/hour for each 40-mg/dL (2.2-mmol/L) increase in glucose level over 100 mg/dL up to 2.5 units/hour for levels > 220 mg/dL (> 12.2 mmol/L)

• Every hour during labor: Measurement of glucose level at bedside and adjustment of dose to keep the level at 70 to 120 mg/dL (3.8 to 6.6 mmol/L)

• If the glucose level is significantly elevated: Possibly additional bolus doses

For spontaneous labor, the procedure is the same, except that if intermediate-acting insulin was taken in the previous 12 hours, the insulin dose is decreased. For women who have fever, infection, or other complications and for women with obesity who have type 2 and have required > 100 units of insulin/day before pregnancy, the insulin dose is increased.

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 hours.

During the first 6 weeks postpartum, the goal is tight glucose control. Glucose levels are checked before meals and at bedtime. Breastfeeding is not contraindicated but may result in neonatal hypoglycemia if oral hypoglycemics are taken. Women who have had gestational diabetes should have a 2-hour oral glucose tolerance test with 75 g of glucose at 6 to 12 weeks postpartum to determine whether diabetes has resolved.

1. 1. American College of Obstetricians and Gynecologists' Committee on Practice Bulletins—Obstetrics. ACOG Practice Bulletin No. 201: Pregestational Diabetes Mellitus. Obstet Gynecol 132(6):e228-e248, 2018. doi:10.1097/AOG.0000000000002960

2. 2. Miller E, Hare JW, Cloherty JP, et al: Elevated maternal hemaglogin A1c in early pregnancy and major congenital anomalies in infants of diabetic mothers. N Engl J Med 304 (22):1331–1334, 1981. doi: 10.1056/NEJM198105283042204