Gestational diabetes is defined as glucose intolerance that begins, or is first recognized, during pregnancy. Diabetes means your blood glucose, also called blood sugar, is too high. It is diagnosed for the first-time during pregnancy (usually between the 24th and 28th week of pregnancy). Gestational diabetes may resolve at the end of pregnancy, but a small percentage of women develop life-long diabetes after being diagnosed with gestational diabetes.
What causes gestational diabetes?
The exact cause of gestational diabetes mellitus is unknown. However, researchers and medical experts suggest that it is due to insulin resistance caused by the hormones produced by the placenta (the organ that helps transport nutrients and waste products between the growing baby and the mother).
The placenta supplies the growing fetus with nutrients and water and produces a variety of hormones to help maintain the pregnancy. These hormones include estrogen, cortisol and human placental lactogen that can have a blocking effect on insulin (a hormone that regulates blood sugar). This is called a contra-insulin effect.
As the placenta grows, more of these hormones are produced and they overwhelm the body’s ability to use insulin (insulin resistance). In the absence of insulin, the blood sugar gets high resulting in gestational diabetes. All pregnant women have some insulin resistance during late pregnancy, and most women can overcome the insulin resistance. Those who do not overcome this develop gestational diabetes.
Who is at risk of developing gestational diabetes?
Some women are at greater risk of gestational diabetes than others. The following increases the risk of gestational diabetes:
overweight and obesity (preconception)
previous gestational diabetes
family history of diabetes
previously delivering a baby weighing more than 4.1kg
race (black and hispanic women have a higher risk of developing gestational diabetes)
advanced maternal age
polycystic ovary syndrome or other health condition lined to insulin
high blood pressure, high cholesterol, heart disease or other medical conditions.
Symptoms of gestational diabetes
Most women do not show symptoms of gestational diabetes and it is often only discovered during a routine screening. However, some symptoms include being thirstier than usual, increase in hunger and more frequent urination.
How is gestational diabetes diagnosed?
Women who are at risk of gestational diabetes are usually screened around the 24th and 28th week of pregnancy. The screening involves a two-part test, (the glucose challenge test, and the glucose tolerance test).
Glucose challenge test: For this test, you drink a sweet liquid. After about an hour, you will have a blood test to check your blood sugar level. If your blood sugar level is high, your doctor will perform a glucose tolerance test.
Glucose tolerance test: an oral glucose test is only done if your challenge test results are abnormal. For this test, you fast (do not eat for 8 hours) before the tolerance test. Then the doctor or nurse draws your blood before and after you drink a sweet liquid. The glucose tolerance test can confirm a diagnosis of gestational diabetes.
Complications of gestational diabetes
If gestational diabetes is not carefully managed it can lead to complications for the mother and the baby. The most common complications that may ensue from uncontrolled blood sugar levels are as follows:
Excessive birthweight: Higher than normal blood sugar in mothers can cause babies to grow too large (macrosomia). Babies born from mothers with gestational diabetes may be as large as 4kg. These babies are more likely to become wedged in the birth canal, have birth injuries, and may need a c-section delivery.
Stillbirth: Untreated gestational diabetes can result in a baby’s death either before or shortly after birth.
Low blood sugar(hypoglycemia) in the baby: Babies born from mothers with gestational diabetes may have low blood sugar (hypoglycemia) shortly after birth. Severe episodes of hypoglycemia my cause seizures in the baby.
Risk of obesity and type 2 diabetes: Babies of mothers who have gestational diabetes are at higher risk of developing obesity and gestational diabetes later in life. Women that develop gestational diabetes may develop type 2 diabetes after pregnancy.
Premature birth: Gestational diabetes can lead to pre-term delivery.
Pre-eclampsia: Women with gestational diabetes are at an increased risk of developing pre-eclampsia (high blood pressure disorder that occurs in pregnancy).
How can gestational diabetes be prevented?
Gestational diabetes cannot always be prevented as there are non-modifiable risk factors that predispose some women (genes). However, obesity is a prime determinant for developing gestational diabetes. Maintaining a healthy weight and following a well balanced nutritional plan, both before and during pregnancy, can decrease your chances of developing gestational diabetes.
Management of gestational diabetes
Many women with gestational diabetes can manage their blood glucose levels by following a healthy eating plan and being physically active. However, some women may need insulin or medication to control their blood sugar levels. Women diagnosed with gestational diabetes are usually managed by an obstetrician because they are considered high risk patients.
Take home message
Gestational diabetes is a serious medical condition with many complications for the mother and the baby. The best advice is to maintain a healthy weight before and after pregnancy through diet and a healthy lifestyle.
This article is written by Dr Itumeleng Buti MBChB( Pret)
References:
1. Buchanan TA, Xiang A, Kjos SL, Watanabe R. What is gestational diabetes?. Diabetes care. 2007 Jul 1;30(Supplement_2):S105-11.
2. Bottalico JN. Recurrent gestational diabetes: risk factors, diagnosis, management, and implications. InSeminars in Perinatology 2007 Jun 1 (Vol. 31, No. 3, pp. 176-184). WB Saunders.
3. National Institute of Diabetes and Digestive and Kidney disease. Health Information: Gestational Diabetes. [Internet] National Institute of Diabetes and Digestive and Kidney disease; Boyd Metzger; [Cited 2022 February 8] Available from: https://www.niddk.nih.gov/health-information/diabetes/overview/what-is-diabetes/gestational.
4. Center of Disease Control and Prevention. Diabetes basics: Gestational Diabetes.[ Internet] US department of Health & Human Services. [Updated 2021 August 10; Cited 2022 February 8] Available from: https://www.cdc.gov/diabetes/basics/gestational.html.
John Hopkins Medicine. Conditions and diseases: Gestational Diabetes.[ Internet] John Hopkins Medicine.[Cited 2022 February 08]. Available from:https://www.hopkinsmedicine.org/health/conditions-and-diseases/diabetes/gestational-diabetes
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