Gestational Diabetes Mellitus

          Gestational diabetes mellitus is a form of diabetes mellitus which affects pregnant women. It is believed that the hormones produced during pregnancy reduce a woman's receptivity to insulin, leading to high blood sugar levels. Gestational diabetes mellitus affects about 4% of all pregnant women. It is estimated that about 135,000 cases of gestational diabetes mellitus arise in the United States each year.

          Hormones involved in development of placenta, which helps the baby to develop also blocks, the action of the mother's insulin in her body. This problem is called insulin resistance. During pregnancy a mother may need up to three times more insulin for glucose to leave the blood and transform to energy. When body is not able to use insulin due to insulin resistance it develops into Gestational Diabetes mellitus. Glucose builds up in the blood to high level, it is called hyperglycemia.

          Gestational diabetes mellitus affects the mother in late pregnancy and the baby too. Insulin does not cross the placenta, as glucose and other nutrients do. Extra blood glucose passes through the placenta that gives the baby a high blood glucose level. It results the baby's pancreas to make extra insulin to get rid of the blood glucose. Since the baby is getting more energy than it needs to develop and grow, the extra energy is stored as fat. It can lead to Macrosomia i.e. “Fat” baby. At birth this fat baby develops problem in breathing or may develop hypoglycemia due to over production of insulin.

Types of Gestational Diabetes Mellitus

The two subtypes of gestational diabetes mellitus (diabetes mellitus which began during pregnancy) are:

Type A1gestational diabetes mellitus

     Abnormal oral glucose tolerance test (OGTT), but normal blood glucose levels during fasting and two hours after meals; diet modification is sufficient to control glucose levels

Type A2 gestational diabetes mellitus

     Abnormal OGTT compounded by abnormal glucose levels during fasting and/or after meals; additional therapy with insulin or other medications is required

The second group of diabetes mellitus which existed prior to pregnancy is also split up into several subtypes.

Type B gestational diabetes mellitus: onset at age 20 or older or duration of less than 10 years.

Type C gestational diabetes mellitus: onset at age 10-19 or duration of 10–19 years.

Type D gestational diabetes mellitus: onset before age 10 or duration greater than 20 years.

Type E gestational diabetes mellitus: overt diabetes mellitus with calcified pelvic vessels.

Type F gestational diabetes mellitus: diabetic nephropathy.

Type R gestational diabetes mellitus: proliferative retinopathy.

Type RF gestational diabetes mellitus: retinopathy and nephropathy.

Type H gestational diabetes mellitus: ischemic heart disease.

Type T gestational diabetes mellitus: prior kidney transplant.

An early age of onset or long-standing disease comes with greater risks, hence the first three subtypes.

Symptoms of Gestational Diabetes Mellitus

          Usually there are no symptoms, or the symptoms are mild and not life threatening to the pregnant woman. The blood sugar (glucose) level usually returns to normal after delivery.

Symptoms may include:

  • Blurred vision
  • Fatigue
  • Frequent infections, including those of the bladder, vagina, and skin
  • Increased thirst
  • Increased urination
  • Nausea and vomiting
  • Weight loss despite increased appetite

Risk Factors for Gestational Diabetes Mellitus

Classical risk factors for developing gestational diabetes mellitus are 
  • previous diagnosis of gestational diabetes mellitus or prediabetes 
  • Gave birth to a baby that weighed more than 9 pounds or had a birth defect
  • Have high blood pressure
  • Have too much amniotic fluid
  • impaired glucose tolerance, or impaired fasting glycaemia
  • Family history revealing a first-degree relative with type 2 diabetes mellitus
  • Maternal age - a woman's risk factor increases as she gets older (especially women over 35 years of age).
  • Ethnic background (those with higher risk factors include African-Americans, Afro-Caribbeans, Hispanics, Native Americans, Pacific Islanders, and people originating from South Asia)
  • Overweight, obese or severely obese increases the risk by a factor 2.1, 3.6 and 8.6, respectively.
  • Previous poor obstetric history
In addition to this, statistics shows a double risk of gestational diabetes mellitus in smokers. Polycystic ovarian syndrome is also a risk factor, although relevant evidence remains controversial. Some studies have looked at more controversial potential risk factors, such as short stature.

About 40-60% of women with gestational diabetes mellitus have no demonstrable risk factor; for this reason many advocate to screen all women. Typically, women with gestational diabetes mellitus exhibit no symptoms (another reason for universal screening), but some women may demonstrate increased thirst, increased urination, fatigue, nausea and vomiting, bladder infection, yeast infections and blurred vision.

Gestational Diabetes Mellitus Test

          Depending on risk factors, the doctor will decide when you need to be checked for diabetes mellitus. If you are at higher risk, the blood glucose level may be checked at your first prenatal visit. If your test results are normal, you will be checked again sometime between weeks 24 and 28 of your pregnancy.

    Depending on the risk and your test results, you may have one or more of the following tests:

          Fasting blood glucose or random blood glucose test: When plasma glucose level is >126 mg/dl or when random plasma glucose >200 mg/dl is confirmed on a subsequent day then the woman is at risk to develop GDM. Hence, you will be suggested by your doctor to go for some confirmatory tests.

        Screening glucose challenge test: It is a preliminary screening test, which is performed between 26-28 weeks. This test will diagnose whether diabetes mellitus exists or not by indicating whether or not the body is using glucose. The Glucose Challenge Screening is now considered to be a standard test performed during the second trimester of pregnancy.

       Oral glucose tolerance test (OGTT): Women who are considered at risk for gestational diabetes mellitus are being asked to go for this test. The glucose challenge is performed by giving 1.76 oz of glucose drink and then drawing a blood sample an hour later and measuring the level of blood glucose present. Women with a blood sugar level greater than 140 mg/dl may have gestational diabetes mellitus, and require a follow up test called a 3-hour oral glucose tolerance test (OGTT).

According to ADA following values are considered to be abnormal for the OGTT:

  • Fasting Blood Glucose Level=95 mg/dl
  • 1 Hour Blood Glucose Level=180 mg/dl
  • 2 Hour Blood Glucose Level=155 mg/dl
  • 3 Hour Blood Glucose Level=140 mg/dl

Treatment for Gestational Diabetes Mellitus

          Women with gestational diabetes mellitus have healthy pregnancies and healthy babies if, they follow a treatment plan from their health care provider. It is required to keep your blood glucose levels in a target range. Each woman should have a specific plan designed just for her needs, so one can follow these general tips to stay healthy with gestational diabetes mellitus:

Watching Your Baby

          Your health care provider should closely check both you and your baby throughout the pregnancy. Fetal monitoring to check the size and health of the fetus often includes ultrasound and nonstress tests.

          A nonstress test is a very simple, painless test for you and your baby. A machine that hears and displays your baby's heartbeat (electronic fetal monitor) is placed on your abdomen. When the baby moves, the baby's heart rate normally increases 15 - 20 beats above its regular rate.

          Your health care provider can compare the pattern of your baby's heartbeat to movements and find out whether the baby is doing well. The health care provider will look for increases in the baby's normal heart rate occurring within a certain period of time.

Diet and Exercise
          The best way to improve your diet is by eating a variety of healthy foods. You should learn how to read food labels, and check them when making food decisions. Talk to your doctor or dietitian if you are a vegetarian or on some other special diet.

         In general, your diet should be moderate in fat and protein and provide controlled levels of carbohydrates through foods that include fruits, vegetables, and complex carbohydrates (such as bread, cereal, pasta, and rice). You will also be asked to cut back on foods that contain a lot of sugar, such as soft drinks, fruit juices, and pastries.

          You will be asked to eat three small- to moderate-sized meals and one or more snacks each day. Do not skip meals and snacks. Keep the amount and types of food (carbohydrates, fats, and proteins) the same from day to day.

          Your doctor or nurse will prescribe a daily prenatal vitamin. They may suggest that you take extra iron or calcium. Talk to your doctor or nurse if you're a vegetarian or are on some other special diet.

          Remember that "eating for two" does not mean you need to eat twice as many calories. You usually need just 300 extra calories a day (such as a glass of milk, a banana, and 10 crackers).

          If managing your diet does not control blood sugar (glucose) levels, you may be prescribed diabetes mellitus medicine by mouth or insulin therapy. You will need to monitor your blood sugar (glucose) levels during treatment.

         Most women who develop gestational diabetes mellitus will not need diabetes mellitus medicines or insulin, but some will.

          Women with gestational diabetes mellitus should note down their blood sugar level, physical activity and everything she eats and drinks, in a daily record book. This can help track how well the treatment is working and what is to be done further to maintain the normal blood sugar level. Some women with gestational diabetes mellitus will also need to take insulin, to help manage their diabetes mellitus if blood sugar is shooting up, in spite of all this.  The extra insulin can help them lower their blood sugar level.

Related article

Does having gestational diabetes put me at higher risk for diabetes mellitus in the future?
How does having gestational diabetes mellitus affect my pregnancy and my baby?


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