Definition of "Gestational diabetes"

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Gestational diabetes [mellitus] (GDM) occurs when pregnant women without a previous Hx of diabetes, develops hyperglycemia during pregnancy, especially during her 3rd trimester.

Source: NDSS

Patient information

What is gestational diabetes?
Let's break it down. Diabetes is high blood sugar. Gestational just means pregnant. So it's high blood sugar, when you're pregnant.

  • Usually asymptomatic, and it is most commonly Dx by screening during pregnancy
  • Increased thrist
  • Increased urination
  • Fatigue
  • Nausea and vomiting
  • Bladder infection
  • Yeast infections
  • Blurred vision

Patient information

What happens when you have high blood sugar, during pregnancy?
So the same sorts of things in diabetes. So increased thirst, urination. You can also get fatigue, nausea and vomiting. And it can predispose to infection, like of the bladder, and yeast infections. It can affect blood vessels, so cause blurred vision.

  • Insulin receptors don't function properly, likely due to pregnancy-related factors, such as the presence of hPL that interferes with susceptible insulin receptors
  • This causes inappropriately elevated blood sugar levels
Risk factors
  • PCOS, although evidence remains controversial
  • PH of gestational diabetes, prediabetes, impaired glucose tolerance, or impaired fasting glycemia
  • FH of a 1st degree relative w/ T2DM
  • Maternal aging, especially >35yo
  • Ethnicity, w/ higher risk for Africans, Hispanics, and South East Asians
  • Overweight (2.1x), obese (3.6x), or severe obesity (8.6x)
  • PMH of macrosomia (>90th percentile, or >4kg)
  • Poor obstetric Hx
  • Genetic factors
  • Smoking (2x)
  • Short stature, although it is controversial
  • Non-challenge blood glucose tests, used in some jurisdictions, for ultra-early screening, which involves measuring blood glucose without challenging the subject with glucose solutions, including:
    • Random glucose test 11.1+ mmol/L, confirms GDM
    • Fasting glucose test 5.1+ mmol/L, confirms GDM
  • Glucose challenge tests, a 75g to be done at 24 weeks gestation, or in high risk women, a both at 12 weeks and repeated at 24 weeks gestation. In Australia, all women are subject to a screen with a 75g GCT, rather than w/ a non-challenge blood glucose test:
    • Screening, for inappropriately high levels of glucose in blood, which is usually how it is Dx because it is usually asymptomatic
    • Diagnostic, which can be done at the first antenatal visit for a woman in a high-risk pregnancy (e.g. PCOS, or acanthosis nigricans). Levels include:
      • 1 hour 10+ mmol/L
      • 2 hour 8.5+ mmol/L
      • Fasting (>2 hours) 5.1+ mmol/L
    • Post-pregnancy screening:
      • Repeat OGTT, 6 weeks after delivery, to confirm that diabetes has dissapeared
      • Afterwards, T2DM should be regularly screened too
  • Not recommended is urinary glucose testing (glucosuria), as although dipstick is practised widely, the sensitivity is low. Also, increased GFR during pregnancy can contribute to 50% of women having glucose in their urine, so it also lacks specificity

Source: NSW Health

Patient information

How do you know whether someone has this pregnancy version of high blood sugar?
You can do tests that are non-challenge. Or challenge. Non-challenge are screening tests, you can do it randomly, after not having eaten for a while, or 2 hours after a meal.

How does glucose challenge test work?
Challenge is where you give someone a certain amount of sugar, and see how they respond. Specifically, it's defined as 10+ mmol/L after 1 hour, 8.5+ mmol/L after 2 hours, or 5.1+ mmol/L whilst fasting.

Why are there different figures for fasting, 1 hour, 2 hours though?
Obviously, straight after a meal, it's permitted to be higher, so over time, the threshold goes down. And if you've fasted, which you can view as the MOST amount of time, it's the absolute lowest threshold.

And random. That's set at the absolute highest, at 11.1+ mmol/L?
That's because you could've just eaten. Which would've shot it up.

  • U/S, to monitor development of macrosomia
  • HbA1c, to determine glucose control over a longer period of time

Patient information

Apart from the sugar tests, what else can you do?
Ultrasound, to see whether there's a big baby. And HbA1c, to see what blood sugar is like over time.

  • Prevention, including:
    • Ingesting more fiber in foods w/ whole grains, fruits, and vegetables
    • Breastfeeding, to reduce risk of diabetes, and related risks for both mother and child
  • Lifestyle modification, including:
    • Modified diet and introduction of moderate exercise together can sometimes even control gestational diabetes. Food plan, is 1st line. Diet modifications should avoid peaks in blood sugar, which can be done by spreading carbohydrate intake over meals, and using slow-GI releasing carbohydrate sources. Since insulin resistance is highest in mornings, breakfast carbohydrates need to be restricted more
    • Regular moderately intense physical activity, although it has not been found to be significant for primary prevention of GDM, but it may be used as tertiary prevention for women who have already developed the condition
    • Smoking cessation
  • Antidiabetic drugs, in GDM which is uncontrolled on diet and medication:
    • Insulin therapy, mostly fast-acting insulin, before eating to blunt glucose rises after meals. Care needs to be taken to avoid hypoglycemia due to excessive insulin. More injections can result in better control but requires more effort, and there is no evidence it has greater benefits
    • Metformin, if required, may be better than just insulin. There is some evidence it is safe, or at least less dangerous to the fetus than poorly controlled diabetes. Metformin without insulin is asociated with greater weight gain, insufficient control, and in the absence of studies, long term complications from metformin. However, babies born Tx with metformin have been found to develop less visceral fat, thus less prone to insulin resistance in later life
  • Education, regarding self monitoring of blood glucose levels, which should aim for:
    • Fasting capillary BGL <5.5mmol/L (cf 5.1)
    • 1 hour postprandial capillary BGL <8mmol/L (cf 10)
    • 2 hour postprandial BGL <7mmol/L (cf 8.5)

Patient information

What can you do about high blood sugar in pregnancy?
It would've been good to prevent it. So that involves eating more fibrous foods, and breastfeeding. Altering lifestyle can help if you've already got it. So a healthy diet that is low carb, as well as exercising helps. Stop smoking if that's the case.

How about drugs?
Insulin helps reduce blood glucose, but make sure not to give too much or blood glucose will fly the other way (become too low). And metformin, but is only tried after giving insulin, which has better outcomes both in terms of blood glucose control, as well as its effects on the baby. Patients should also be taught how to monitor their blood glucose levels themselves.

  • Gestational diabetes is a treatable condition and women who have adequate control of glucose levels can effectively decrease these risks
  • Gestational diabetes usually self resolves after birth
  • Women who have inadequately controlled glucose levels can result in less serious fetal complications (e.g. macrosomia), and increase maternal quality of life

Patient information

What can I expect in the long term if I have high blood glucose during pregnancy?
It usually fixes itself after birth. And controlling it helps both the baby as well as the mother.

  • For the child:
    • LGA, which may lead to delivery complications
    • Hypoglycemia (low blood sugar)
    • Jaundice
    • Seizures
    • Stillbirth
    • Childhood obesity
    • T2DM later in life
  • For the mother:
    • T2DM, or very rarely, T1DM, following pregnancy
    • Pre-eclampsia
    • C section

Patient information

What bad things can happen as a result of high blood glucose during pregnancy?
There are bad things that can happen to the mother, as well as for the child. For the child, they can be big, due to drugs the mother is taking they can get LOW blood sugar, when they grow up they can become obesity or have diabetes. For the mother, they can get type 2 diabetes later on, get protein in their urine (called pre-eclampsia), and they might require a C section to deliver the baby.

  • Affects 6% of pregnancies
  • 50% of women w/ GDM have no risk factors, thus it is advocated that all women be screened. The lack of Sx is another reason for universal screening
  • Tx of GDM is controversial, as it has been accompanied w/ more infants admitted to neonatal wards and more IOL's, w/ no proven decrease in C section rates or perinatal mortality

Patient information

How common is high blood glucose during pregnancy?
It affects 3 in every 50 pregnant women. 1 in 2 women get it without any reason, there's no reason to think that they'd get it, and that's why we screen ALL women.

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Definition of Gestational diabetes | Autoprac

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