Gestational Diabetes Screening
aka Blood sugar testing, glucose tolerance testing, or GTT

What is Diabetes?

Diabetes is a serious disease that impairs the body’s use of glucose, overworks the pancreas, and causes long-term damage to tiny capillaries in the body.  It begins when too much glucose, the energy molecule that comes from our food, is present in circulation.  The pancreas is required to produce insulin, the hormone responsible for getting glucose into cells and balancing blood glucose levels, in great quantities and irregular spurts.  Basically, this wears the pancreas out and makes the body’s cells less responsive to insulin over time.  The extra blood glucose causes capillaries to burst, impeding blood flow and tissue repair.  Type 1 diabetes is the result of infection in the pancreas, is irreversible, and often attacks during childhood.  Type 2 diabetes is the most common today, is largely caused by diet and lifestyle, and is affecting adults and children alike.

What is Gestational Diabetes?

During pregnancy, the mother’s body is required to change its metabolism so that the baby is constantly supplied with adequate levels of glucose and protein.  In essence, she regulates her glucose levels up.  This is a normal and healthy physiological reaction. However, when a mother has pre-existing glucose metabolism problems, this normal change can be too much for her body.  Her pancreas is forced to produce insulin too often, her glucose levels fluctuate wildly, and her body “resets” itself to this irregular metabolism.  Therefore, gestational diabetes mellitus (GDM) is the onset of Type 2 diabetes during pregnancy.  it can be mild or severe and it can go away after pregnancy.  It may occur in one pregnancy but not again in another.  It affects 2-10% of pregnancies in the US.

Problems caused by GDM

GDM can cause problems for both the mother and the baby, during and after pregnancy.  The mother has an increased risk or pre-eclampsia (extreme rise in blood pressure), hypertension, and polyhydramnios (too much amniotic fluid).  The baby is a higher risk of birth injury due to macrosomia (larger than normal) or of hypoglycemia after birth, with increased likelihood of breathing difficulties and hospitalization. Additionally, the mother’s risk of developing Type 2 increases substantially.

A very important but minimally understood negative effect of GDM is the “resetting” of the baby’s own metabolism that occurs as the baby’s pancreas, brain chemicals, and body cells react to the high levels of glucose during pregnancy.  The child is pre-programmed to crave sugar, have radical swings in insulin levels, and gain weight.  This vastly increases the child’s risk of developing Type 2 as a child, teenager, or adult.  Diabetes can be intergenerational; that is, if you have GDM and your baby is a girl who goes on to have her own children, the of her children developing diabetes is increased.

What are the risk factors for GDM?

Pregnancy itself is not a cause of GDM, but rather a situation in which a metabolic problem may become apparent.  GDM is largely associated with certain lifestyle and genetic factors. Some documented risk factors for developing gestational diabetes include:

      • maternal age >25 years
      • pre-pregnant BMI (body mass index) > 28
      • history of gestational diabetes or glucose intolerance
      • family history of diabetes in first-degree relative (e.g. mother or father)
      • member of an ethnic group of high prevalence of gestational diabetes (African American, Alaskan Native, Hispanic American, Native American, South or East Asian, Pacific Islander)
      • previous infant with birth weight >4000 grams
      • history of previous unexplained stillbirth
      • polyhydramnios
      • polycystic ovarian syndrome
      • obstetrical history including poor outcomes (such as miscarriages and congenital anomalies)

While a person cannot change her ethic group, family members, or health history, each mother can positively impact her glucose metabolism with education and changes in diet and exercise patterns.

Can we test for GDM?

The glucose tolerance test (GTT) is the current standard of care.  It is done between 24-28 weeks gestation in order to identify when mothers are at risk of GDM and then have time to positively affect the pregnancy.  Usually, the GTT is done in the morning after fasting all night.  The mother has a fasting blood sugar level drawn, drinks “the nasty orange drink” (a standard glucose load), and then has her blood sugar level drawn again at 1 hour or at 2 hours.  Sometimes it is drawn at 1, 2, and 3 hours after “the drink”.

Alternatives to the GTT include: a random blood sugar level (either by blood draw or finger poke);or eating a large meal instead of drinking “the drink”.  Ask your midwife for details.

Normal blood glucose values:  before meals < 95 mg/dL, 1 hr after meal <130mg/dL, 2 hr after meal <120mg/dL.

What happens if the test results are abnormal?

The key to a healthy pregnancy is a healthy diet full of nutrients and a healthy lifestyle that includes exercise and adequate rest.  Processed and fast foods are discouraged as they contain diabetes-promoting sugars, “fake” sugars, preservatives, dyes, and chemicals, but contain very little by way of nutritional value.  Your midwife is not your “diet police” but a guide toward careful assessment of how you can make healthier choices.

After an abnormal GTT, mothers receive intensive diet and exercise counseling with the expectation of managing blood sugars in this manner.  If dietitian, CNM, or MD care is required, mothers are referred as necessary.  Clients with GDM and uncontrollable blood glucose levels will be transferred, according to homebirth protocols.

Unfortunately, the GTT is only partially effective in identifying those mothers who are at risk of developing GDM and tends to over-diagnose the problem.  It does not take into account the individual woman’s diet and lifestyle, it moves the focus of therapy from effective diet and exercise management to medical and drug management, and it causes pregnancy to viewed as pathological rather than healthy.  The studies upon which the standard guidelines are based did not differentiate between mothers with good or bad diets prior to and during pregnancy, those with access to healthy lifestyles and food, and those that achieved normal tests after an abnormal test.

How can I avoid developing GDM in the first place?!?

The key to overall health AND regulating glucose levels is, not surprisingly, a HEALTHY LIFESTYLE which includes DAILY INTAKE OF FRESH FOODS WITH HIGH NUTRITIONAL DENSITY, EXERCISE, AND HEALTHY FOOD CHOICES.  Of course, the longer you have done this prior to pregnancy, the better your health in general will be.  Some women will develop GDM regardless of their risk factor and lifestyle, however.

More information

UpToDate:
http://www.uptodate.com/contents/gestational-diabetes-mellitus-beyond-the-basics
http://www.uptodate.com/contents/medical-management-and-follow-up-of-gestational-diabetes-mellitus
http://www.uptodate.com/contents/screening-and-diagnosis-of-diabetes-mellitus-during-pregnancy http://www.uptodate.com/contents/obstetrical-management-of-pregnancies-complicated-by-gestational-diabetes-mellitus

CDC:
http://www.cdc.gov/pregnancy/diabetes-gestational.html
http://www.cdc.gov/features/diabetespregnancy/
http://www.cdc.gov/diabetes/pubs/pdf/gestationalDiabetes.pdf

ACOG:

ACOG article 1