All about Gestational Diabetes Mellitus (GDM)

By Dr. Girish Parmar in Endocrinology

Apr 24 , 2023 | 4 min read

What is Gestational Diabetes Mellitus?

Gestational Diabetes Mellitus (GDM) is a specific type of diabetes (high blood glucose levels) that only occurs during pregnancy. It is temporary and usually goes away after the birth of your baby.

What are your chances of developing GDM?

Approximately one in 20 pregnant women will develop gestational diabetes, usually between 24 and 28 weeks of pregnancy. Gestational diabetes can have significant effects for you and your baby if not well controlled.

You have a higher risk of developing GDM if you:

Are over 30 years of age

  • Are overweight: BMI > 23kg Im2 or obese BMI > 25kg Im2
  • Are from certain ethnic backgrounds — Indigenous Australian, Torres Strait Islander, Indian, Vietnamese, Chinese, Middle Eastern, Polynesian or Melanesian
  • Have had GDM in a previous pregnancy
  • Have had prior difficulty carrying a pregnancy to term
  • Have previously given birth to baby weighing more than 4kg
  • Are a woman with polycystic ovarian syndrome
  • Are a woman taking certain medication e.g. Corticosteroids, Antipsy- chotics
  • Have a family history of Type 2 diabetes

How does GDM affect me?

Gestational Diabetes Mellitus raises your risk of high blood pressure, as well as preeclampsia — a serious complication of pregnancy that can threaten the lives of both mother and baby.

It also increases the risk of:

  • Pre-term delivery
  • Increased rate of cesarean delivery
  • Birth trauma, postpartum hemorrhage
  • Future risk for Type 2 diabetes mellitus as well as other aspects of the metabolic syndrome, such as obesity, cardiovascular morbidities and recurrent GDM

How does GDM affect my baby?

Glucose (sugar) crosses the placenta so your baby is exposed to your higher BGL. This stimulates your baby's pancreas to produce more insulin. It is the extra insulin that causes your baby to grow bigger and fatter. Untreated or uncontrolled GDM can mean problems for your baby such as:

  • Being born very large and with extra fat (this can make delivery difficult and more dangerous for the baby)
  • Low blood glucose levels after birth
  • Breathing difficulties
  • Requiring admission to a special care nursery
  • Feeding problems
  • Problems maintaining body temperature
  • An increased risk of developing diabetes or obesity later in life

How do I know if I have GDM?

  • As per Diabetes in Pregnancy Study Group of India (DIPS!) practice guidelines, all pregnant women are now screened for GDM.
  • This involves an oral glucose tolerance test (OGTT) between 24 and 28 weeks of pregnancy. If the result is negative, the test is repeated around 32 and 34 weeks of pregnancy.
  • You will be given a 75 g glucose load, irrespective of whether you are in a fasting or non-fasting state, and without regard to the time of the last meal. A blood sample is collected after 2 hours to estimate blood glucose levels.
  • This test may be performed earlier in your pregnancy if there is a clinical reason to do so


With 75gm OGTT

  • 2 hours 140mg/d1 Gestational Diabetes mellitus (GDM)
  • 2 hours 120mg/d1 Decreased Gestational Glucose Tolerance (DGGT)
  • You may be asked to do HbA1c level if detected in the early pregnancy with high blood glucose levels
  • HbA1c 5.7% - 6.4% Increased risk of GDM
  • HbA1c 6.5% GDM

How is GDM treated?

The aim of the treatment is to keep your Blood Glucose Levels (BGL) within the normal range for the rest of your pregnancy.

Target blood glucose levels:

  • Fasting <95mg/dI
  • 2 hours after meals <120mg/dI

These targets can be achieved with a healthy diet, regular exercise and medication. You will be asked to monitor your Blood Glucose Levels at home frequently, or as directed by your doctor.

You may be asked to check your blood glucose:

  • When you wake up
  • Just before meals
  • 1 or 2 hours after breakfast
  • 1 or 2 hours after lunch
  • 1 or 2 hours after dinner


Your blood pressure will be monitored during each visit. Every trimester, you will be monitored for protein in urine and undergo an examination of the fundus. Women with gestational diabetes are increasingly being able to have healthy pregnancies and healthy babies because they follow their treatment plan and control their blood sugar.

What happens after the birth of my baby?

Usually the GDM goes away after the birth of your baby. However, there is a 40 percent chance of developing GDM during your next pregnancy and a 7-times higher risk of developing Type 2 diabetes mellitus later in life. You will be asked to repeat your glucose tolerance test six to eight weeks after your baby's birth. If this test is within the normal range, you will be asked to check your blood glucose levels every one to two years.

How can I prevent or delay Type 2 diabetes later in life?

  • Watch your weight. Six to twelve months after your baby is born, your weight should be back to what you weighed before you got pregnant. Lower the pre-pregnancy weight, lower are the chances of GDM.
  • If you still weigh too much, work towards losing 5% to 7% of your body weight.
  • Follow a healthy diet, maintain a healthy weight and exercise regularly- ly to help minimize the risk of developing Type 2 diabetes mellitus in the future.


  • Eat a healthy diet
  • Exercise and be active
  • Check your blood sugar as directed
  • Take your medicine as directed
  • See your doctor regularly

Also Read About High-Risk Pregnancy Management


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