Gestational Diabetes

Question 1

Definition of gestational diabetes mellitus

Answer 1

• Any degree of glucose intolerance with onset or first recognition during pregnancy.
• This does not exclude the possibility that unrecognized glucose intolerance has antedated or begun concomitantly with the pregnancy.

Question 2

frequency of women with gestational diabetes

Answer 2

• Most common medical complication and metabolic disorder of pregnancy
• Occurring in 2-14% of the population, depending on the population studied.
• This is highest in ethnic groups that have higher incidence of Type 2 diabetes (Hispanic Americans, African Americans, Native Americans and Pacific Islanders).

Question 3

pathophysiology of gestational diabetes

Answer 3

• The metabolic changes during pregnancy are essential for adequate nutrients to be delivered to the developing fetus.
• Early in pregnancy maternal estrogens and progesterone increase and promote beta cell hyperplasia and increased insulin release.
• Increase in peripheral glucose utilization and glycogen storage with reduction in hepatic glucose production results in lower fasting glucose levels.
• Placental steroids and peptide hormones (ie. human chorionic sommatomammotropin, cortisol, prolactin, progesterone and estrogen) rise linearly throughout second and third trimesters.
• These hormones increase tissue insulin resistance and so the demand for insulin increases.
• This becomes apparent between 24^th-28^th week.
• The pancreas releases 1 ½ - 2 ½ times more insulin to respond to the increase in insulin resistance.
• Patients with normal pancreatic function are able to meet these demands.
• Borderline pancreatic function leads to inadequate insulin secretion in the presence of increasing insulin resistance.
• In healthy pregnancies, mean FBG levels decline to an average of 74mg/dl with peak postprandial values rarely exceeding 120mg/dl.
• * Meticulous glucose control during pregnancy has been shown to reduce the risk of macrosomia.

Question 4

detection and diagnosis of gestational diabetes

Answer 4

• Risk assessment should be done at the first prenatal visit.
• Women with clinical characteristics consistent with high risk should undergo testing ASAP:
  
  • advanced maternal age
  • morbid obesity
  • history of GDM
  • glycosuria
  • strong family history of DM
• Average risk patients should have testing done at 24-28 weeks.
• Low risk requires no glucose testing but must meet all the following criteria:
• Age <25yrs
• Weight normal before pregnancy
• Member of an ethnic group with a low prevalence of GDM
• No known diabetes in a first degree relative
• No history of abnormal glucose tolerance
• No history of poor obstetric outcome or macrosomic infant
• There are two approaches to screen for GDM
• One-step approach:
  
  • Perform a diagnostic 3hr oral glucose tolerance test (OGTT) without prior plasma or serum glucose screening. Cost effective in high-risk patients or populations. (Patient needs to be on an unrestricted diet for three days)
• Two-step approach for women at average risk at 24-28wks:
  
  • Screen by measuring the plasma glucose concentration 1 hr after a 50g oral glucose load.
  • If >140mg/dl then schedule a 3 hour OGTT (this identifies 80% of patients with GDM)
  • If criteria of >130mg/dl is used this identifies 90% of patients with GDM).
  • The 3 hr OGTT does not need to be performed on patients with a 1hr 50g glucose screen >185mg/dl or a fasting >126mg/dl.
• The 100g, 3 hour OGTT: Must be done after 3 days of an unrestricted carbohydrate diet and while the patient is fasting. Venous plasma glucose is measured at 1, 2 and 3 hours after a 100g glucose load. A positive test requires that 2 values be met or exceeded. One abnormal value should be followed with a repeat test one month later.
  
  • Criteria of positive 100gm OGTT
  • Fasting glucose: 95mg/dl
  • 1 hour glucose: 180mg/dl
  • 2 hour glucose: 155mg/dl
  • 3 hour glucose: 140mg/dl

Question 5

risk to mother with gestational diabetes

Answer 5

• Immediate risks:
  
  • Increased incidence of cesarean section (30%)
  • Preeclampsia (20-30%)
  • Polyhydraminos (20%)
• Long term risks:
  
  • Recurrent GDM and high risk for developing diabetes (8%/yr)

Question 6

risk to the infant with from gestational diabetes (immediate)

Answer 6

• Macrosomia due to excessive fetal insulin due to increased delivery of glucose and amino acids to the fetus via maternal circulation.
  
  • Typically defined as birth weight above 90th percentile for gestation age or greater than 4000g (8.8lbs).
• Shoulder dystocia due to macrosomia resulting in:
  
  • brachial plexus injury
  • clavicular fracture
  • fetal distress
  • low APGAR scores
• Neonatal hypoglycemia
• With extremely poor glucose control increase risk of fetal mortality due to fetal acidemia and hypoxia.
• When a mom has diabetes, the baby will have LOW BLOOD SUGAR!!!
• TEST QUESTION!!!!

Question 7

risk to the infant form gestational diabetes (long term)

Answer 7

• Increased risk of adolescent obesity
• Increased risk of developing Type 2 diabetes

Question 8

management of gestational diabetes

Answer 8

• Dietary therapy is the foundation for the treatment of GDM.
• The ADA recommended dietary therapy starts with 2000-2500kcal/d (35kcal/kg present pregnancy weight) with 50-60% carbohydrates (35-40%), 10-20% protein and 25-30% fat (<10% saturated fat)
• This is somewhat controversial with some recommending 30kcal/kg if normal weight, 24kcal/kg if overweight and 12kcal/kg for morbidly obese patients.
• In at least half the cases, diet alone will maintain fasting and postprandial blood glucose values within target range.
• Post prandial values have been more strongly associated with the risk of macrosomia
  
  • modest carbohydrate restriction 45% of total calories, may blunt postprandial glucose excursion.
• Glucose monitoring should be done at least weekly with a fasting glucose and a 1 hour post prandial.
• We have patients monitor much more frequently and, depending on the levels, increase the frequency further or decrease the frequency.
• Exercise is an adjuvant therapy in GDM. Fetal safety has been established if the maternal heart rate is maintained <140 beats/minute at durations <1 hour and the mother stays hydrated and does not get over heated.
• Can maintain stable blood glucose throughout pregnancy

Question 9

medical management of gestational diabetes

Answer 9

• No oral diabetes medications are currently approved for use in pregnancy.
• Recent multicenter trial with 400 women with GDM were randomized to either insulin or glyburide after 24wks gestation; maternal glucose control, macrosomia, neonatal hypoglycemia and neonatal outcomes were no different in the two groups.
• Glyburide is not FDA approved for use in pregnancy but growing number of diabetes centers are using this. No other oral medications should be used because only Glyburide has been shown to not cross the placenta.
• Recommendations for initiating insulin therapy are:
  
  • FBG >105mg/dl
  • 1 hour PPG >140mg/dl
  • Macrosomia maybe further reduced if insulin is initiated when FBG >95mg/dl.
• Targets
  
  • fasting 60-90mg/dl
  • Preprandial values 60-105mg/dl
  • 1 hr PPG < 130mg/dl
  • 2-6am value 60-90mg/dl.
• NPH, Regular, aspart, Lispro and detemir are category B
• Insulin glargine is pregnancy category C. Lantus insulin has high affinity to IGF-1 receptors, it is unclear what, if any, risks this poses to a fetus but, at this point, not recommended in pregnancy

Question 10

imaging studies/procedures for gestational diabetes

Answer 10

• Growth ultrasound for fetal sized should be done once at 36-37wks gestation.
• Amniocentesis for fetal lung profile if delivery is contemplated prior to 39wks gestation.

Question 11

peripartal management

Answer 11

• The goal of management of third trimester pregnancies in women with diabetes are to prevent still birth and asphyxia.
• Monitoring fetal growth is essential to select proper timing and route of delivery. This is done by frequent testing for fetal well-being and serial ultrasound examinations.

Question 12

delivery timing

Answer 12

• Patients with uncomplicated, diet controlled GDM are allowed to progress to term unless other complications arise.
• Fetal movement counting should be performed by all patients after 28wks gestation.
• Amniocentesis should be performed to document fetal pulmonary maturity if delivery before 39wks gestation is indicated.
• Increase rate of shoulder dystocia with the birth weight of IGDM exceeds 4000g. Estimated fetal weight plays a major role in decision making process for route of delivery. This is done by serial ultrasounds

Question 13

postpartum follow up

Answer 13

• Follow up is crucial in women with GDM
  
  • All should received counseling regarding the high risk for recurrent GDM in future pregnancies
  • Screening for diabetes should be done at the 6wks post partum visit. If this is normal reassessment of glycemia should be done at a minimum of 3 year intervals.
  • Women with impaired fasting glucose or impaired glucose tolerance should be monitored annually.
• A weight loss program consisting of diet and exercise should be instituted for women with GDM in order to improve insulin sensitivity an attempt to prevent the development of Type 2 diabetes.
• All women should be encouraged to breastfeed unless difficulties in glycemic control arise. These women appear to have a lower incidence of developing Type 2 diabetes mellitus. It also appears to decrease the risk of developing infant obesity and impaired glucose tolerance.