Gestational diabetes mellitus (GDM) is a type of diabetes that develops during pregnancy in women who did not have diabetes before becoming pregnant.
GDM is often diagnosed between weeks 24-28 of pregnancy. However, it can be screened early if you have certain risk factors. In most cases, GDM resolves once the baby is born. However, it is an early indication that you may develop type II diabetes in the future.
Gestational diabetes is one of the most common health issues among pregnant women. It affects roughly 5% of all pregnancies, resulting in approximately 200,000 cases each year. If left untreated, gestational diabetes can harm both mother and fetus. Early diagnosis and treatment can help manage the condition and its complications.
What are symptoms of GDM?
Gestational diabetes mellitus (GDM) usually has no obvious signs or symptoms, which is why prenatal screening exams are so crucial. However, a small number of people may exhibit symptoms such as:
- Increased hunger or thirst
- Frequent urination
- Blurred vision
- Unusual fatigue
- Nausea or vomiting
- Frequent infections of the bladder, vagina, or skin
- Weight gain (more than recommended for your pregnancy)
Since many of the symptoms of GDM are similar to normal pregnancy symptoms, they may go unnoticed. Therefore, it is important to understand your risk factors before pregnancy planning.
What causes GDM?
Gestational diabetes mellitus (GDM) results in high blood glucose levels.
- Glucose is produced when your body digests carbs.
- Insulin is a hormone that allows glucose to enter your cells.
- Your body then uses or stores glucose for energy.
During pregnancy, your body requires more insulin than usual. This is because the placenta releases hormones that make your body more resistant to insulin. Most women can produce enough insulin to overcome this resistance. However, some women are unable to produce enough insulin, causing blood glucose levels to rise above typical normal levels.
What are risk factors for GDM?
Common risk factors of gestational diabetes mellitus (GDM) include:
- History of gestational diabetes
- Family history of diabetes
- Being obese or overweight
- Being older than 35
- Long-term steroid use
- History of large babies
- Multiple pregnancies
- Suspected macrosomia (baby is bigger than what is expected at that gestational age)
- History of unexplained stillbirth
- African American, Latino, Native American, Asian American, or Pacific Islander heritage
- Lack of physical activity
- History of high blood sugar, heart disease, high blood pressure, or high cholesterol
- Polycystic ovary syndrome
- Acanthosis nigricans, discoloration of the skin
- Recurrent vaginal candidiasis or fungal skin infection
How is GDM diagnosed?
Blood tests are used to diagnose gestational diabetes. Most pregnant women are tested between weeks 24-38, but women with risk factors may undergo testing earlier in the pregnancy.
A screening glucose tolerance test involves consuming a sugary beverage and having your blood collected an hour later to measure your glucose levels. If the screening test results are abnormal, you may require more testing:
- Blood glucose levels are checked 1 hour after consuming a sugary beverage
- An oral glucose tolerance test is ordered if blood sugar levels are higher than normal, (recommended range for someone without diabetes is 70-140 mg/dL).
- You must fast overnight before the oral glucose tolerance test.
- Blood sugar levels are monitored while fasting, then 1, 2, and 3 hours after consuming a sugary beverage.
- If the test shows two or more elevated blood glucose levels, then the doctor may make a diagnosis of gestational diabetes.
- Fasting blood glucose levels are tested, as well as 1 and 2 hours after consuming a sugary beverage.
- When one or more blood sugar levels are higher than usual, gestational diabetes is diagnosed.
Another test that may be done to confirm a diagnosis of GDM is glycosylated hemoglobin or hemoglobin A1C. This test is used to evaluate long-term blood glucose levels. The hemoglobin A1C level is a measure of the average blood glucose level during the previous 3 months.
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How is GDM managed and treated?
Controlling your blood sugar is the most important aspect of treating gestational diabetes. The goal is to keep your blood glucose level from getting too high.
It is important to be mindful of what you eat, how much you eat, and when you eat. A registered dietitian or certified diabetes educator can help develop a meal plan that is healthy for both you and your baby. Your meal plan should reflect your preferences and consider your general health and fitness level, with the overall goal of keeping your blood sugar levels within the desired range.
When you are physically active, your body uses more glucose for energy, which means less insulin is needed. Your body therefore becomes less insulin resistant.
Regular exercise can also help you keep your weight in a healthy range for pregnancy, lower stress, improve sleep, and boost mood. Try to get at least 30 minutes of exercise a day, whether it is walking, yoga, or another activity approved by your doctor.
Medications or insulin
Most people can keep their blood sugar levels under control with diet and exercise. However, if these measures are not sufficient, your doctor may prescribe insulin or other medications which do not have adverse effects on your baby.
Monitoring your blood sugar
Monitoring your blood sugar levels several times each day will help you get a sense of how well your gestational diabetes is being controlled. Your doctor can show you how to use a blood glucose monitor and give you instructions on when and how often to check your blood sugar.
What are possible complications of GDM?
When gestational diabetes is not effectively managed and blood sugar levels stay too high, potential complications include the following:
Risks to the mother
- Cesarean delivery or a more difficult vaginal birth
- Gestational hypertension or preeclampsia (high blood pressure)
- Type II diabetes in the future (20%-50% risk of developing the condition within 5-10 years of birth)
Risks to the baby
- Premature birth due to excess amniotic fluid
- High birth weight (more than 9 lbs)
- Hypoglycemia (drop in blood sugar levels) at birth
- Shoulders getting stuck in the birth canal during delivery
- Obesity and glucose intolerance in early adulthood (especially if birth weight was above 9 lbs)
- Jaundice, especially if the baby is premature
- Electrolyte imbalance
- Breathing problems
How does GDM affect childbirth and delivery?
When birth planning, your doctor will assess the size of your baby to determine whether you can deliver vaginally. If you have been able to keep your blood glucose under control, your baby's weight is within an appropriate range, you do not have any other pregnancy issues, and you are not on medications, your labor should go normally. Of course, your delivery team will keep an eye on your blood sugar levels the entire time.
If your baby is deemed too big to be delivered vaginally, you will likely be induced at week 38 or 39. You and your doctor can also discuss options such as cesarean delivery.
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Centers for Disease Control and Prevention. Gestational Diabetes. https://www.cdc.gov/diabetes/basics/gestational.html#
Buchanan TA, Xiang AH, Page KA. Gestational diabetes mellitus: risks and management during and after pregnancy. Nat Rev Endocrinol. 2012;8(11):639-649. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4404707/
The University of Iowa. Gestational diabetes (GDM). https://uihc.org/health-topics/gestational-diabetes-gdm
March of Dimes. Gestational Diabetes. https://www.marchofdimes.org/complications/gestational-diabetes.aspx
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