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Gestational Diabetes Screen


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


polycystic ovarian syndrome

obstetrical history including poor outcomes (such as miscarriages and congenital anomalies)


While a person cannot change her ethnic 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 1 hour GTT is done without fasting, however it is recommended that the mother abstain from eating a high sugar snack prior to bedtime, such a ice cream, cookies or cake and avoid a high sugar breakfast such as pancakes and syrup.  We offer 28 Brach's jelly beans, Naked juice (self purchased) or the standard 50 gr orange drink from the lab. We then have you sit down and wait 1 hour until we draw your blood in office.


If the mother does not pass the 1 hour GTT, she will be offered the 3 hour GTT which is much more involved. The mother has a fasting blood sugar level drawn, drinks the orange drink at the lab (a standard glucose load), and then has her blood sugar level drawn again at 1, 2, and 3 hours after "the drink". Fasting after midnight is a must for this test. 

Results usually take 3 days to 1 week to record. 


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