Gestational Diabetes

AUGUST 16, 2021


overview

Gestational diabetes (GDM) is the term used for glucose intolerance that develops during Pregnancy and remits following delivery. The placenta produces a large amount of insulin antagonist hormones, causing hyperglycemia. To maintain glucose homeostasis more insulin is produced. Some women fail to do so resulting in increased blood glucose levels. Gestational diabetes occurs in at least 5% of all pregnancies. Women with gestational diabetes are at increased risk of Type-2 diabetes in the future. The condition is typically asymptomatic and is demonstrated by a blood glucose check-up or oral glucose tolerance test. The diabetogenic effect of pregnancy increases with subsequent pregnancy and obesity. 

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Diagnosis

Women are routinely screened for gestational diabetes between 24 and 28 weeks by 1-hour Glucose Tolerance Test. However, if women have significant risk factors for gestational diabetes, they are screened during the 1st trimester. If the 1st-trimester test is normal, then the test should be repeated at 24 to 28 weeks, if abnormal, then a 3-hour test is done. Abnormal results on both tests confirm the diagnosis. Diagnosis can be made if fasting plasma glucose is greater than 126mg/dl or > 6.9mmole/L or random plasma glucose level of greater than 200mg/dl or >11mmole/L

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Risk factors for developing gestational diabetes include:

  • Gestational diabetes or a macrosomic neonate (weight > 4.5kg at birth) in a previous pregnancy.
  • Unexplained miscarriage or stillbirth.
  • A strong family history of diabetes in 1st-degree relatives.
  • A history of persistent glucosuria.
  • Body mass index (BMI) > 30kg/m2 .
  • Polycystic ovarian syndrome, acanthosis nigricans or other conditions associated with insulin resistance.
  • Multiple pregnancy.
  • Have been on glucocorticoids.
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Effect of pregnancy on diabetes

Insulin requirements increased during pregnancy so patients who were treated with diet alone before pregnancy may need insulin during pregnancy. Ketosis can occur due to increase loss of glucose in the urine. Unrecognized or badly treated diabetes leads to complications in both mother and baby.

Maternal complications

These includes urinary tract infections, candidiasis of vulva and vagina, pregnancy induced hypertension, hydroamnios, and preterm labor.

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Fetal and neonatal complications

These include an increased incidence of congenital abnormalities

  • Major congenital malformation.
  • Intrauterine death in late pregnancy or death soon after birth from hypoglycemia.
  • Spontaneous abortion.
  • Respiratory distress syndrome.
  • Macrosmia: large baby with enlargement of all organs. However, gestational diabetes can result in fetal macrosomia even if blood glucose is kept nearly normal.
  • Polycythemia secondary to intrauterine hypoxia.
  • Hyperbilirubinemia and neonatal jaundice.
  • Hypocalcemia.
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Management

Some women already have Type-2 diabetes, Some women with IDDM  may present for the first time and swift diagnosis is essential to prevent the development of ketoacidosis. Gestational diabetes is managed in exactly the same way as established diabetes. Goals of treatment are:

  • Fasting blood glucose levels at less than 95 mg/dl (< 5.3 mmol/L).
  • 2-hour postprandial levels at less than or equal to 120 mg/dl (≤ 6.6 mmol/L) No wide blood glucose fluctuations.
  • Glycosylated Hb (HbA1c) levels at less than 6.5%.

Good control of the diabetes during the months before conception and during first trimester reduce the incidence of congenital abnormalities.

Diabetic women who have a high HbA1c level, in early pregnancy have an increased tendency to fetal abnormalities. If the pre-conception HbA1c index is high, pregnancy should be postponed until better control of diabetes is achieved. If the glucose levels are more in late pregnancy, the fetus is more likely to be macrosomic.

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Diet and exercise

Caloric intake should be monitored to prevent weight gain of more than 6.8-11.3 kg or in obese women of more than 5.0-9.1 kg. Moderate exercise after meal is advised.

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Insulin

Insulin is advised only if blood sugar is not in controlled with diet. If Fasting plasma level is more than 95 mg/ dl or 2 hour post prandial blood glucose is greater than 120 mg /dl despite a trial of diet therapy for greater than 2 weeks. Insulin cannot cross the placenta and provide more predictable glucose control. It is used for types 1 and 2 diabetes and for some women with gestational diabetes.

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Oral hypoglycemic drugs

Oral hypoglycemic drugs (eg, glyburide) are being increasingly used to manage diabetes in pregnant women because of the ease of administration, 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-2 diabetes before pregnancy, insulin is most often preferred. 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 diabetes require no insulin after delivery. For women with type-1 diabetes, insulin requirements decrease dramatically but then gradually increase after about 72 hours. Oral hypoglycemic taken during pregnancy may be continued during breastfeeding, but the infant should be closely monitored for signs of hypoglycemia. Glucose levels are checked before meals and at bedtime till 6 weeks after delivery. A 2-hour oral glucose tolerance test with 75g of glucose is done in women with gestational diabetes 6 to 12 weeks after delivery to determine whether diabetes has resolved.

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