Gestational Diabetes 1
Screening for Gestational Diabetes in Pregnant Women
Professor Boye
Applied Epidemiology
Section 01 Summer A 2014
June 22, 2014
Casey Guillaume
Gestational Diabetes 2
Background
An analysis by the CDC found that the prevalence of gestational diabetes is nearly 9.2%
(ADA, n.d.). That is nearly 1 in 100 women who will eventually develop gestational diabetes
during pregnancy. Gestational diabetes not only causes potential harm to the mother, but to the
baby as well. It is important for women of childbearing age to a) recognize that they have
diabetes prior to pregnancy and learn to keep blood sugar levels under control, and b) get
screened for gestational diabetes during pregnancy to prevent unwanted adverse health effects.
Diabetes is when the body cannot change sugars and carbohydrates into energy (CDC,
2012). This occurs when the body cannot produce insulin or use what insulin the body produces.
Gestational diabetes mellitus (GDM) is defined as any degree of glucose intolerance with onset
or first recognition during pregnancy (ADA, 2003). Typically, GDM goes away after pregnancy,
but if it does not subside then type 2 diabetes is considered to be present.
How GDM is caused in the body is not well understood. It may be caused by hormones
being released that help the development of the placenta. Those developmental hormones might
block the action of the mother's insulin, causing insulin resistance (ADA, n.d.). This makes it
hard for the mother's body to use the insulin needed for pregnancy.
Uncontrolled or untreated high blood sugar levels in a woman with GDM has increased
chance of (CDC, 2012):

Preeclampsia (high blood pressure, protein in urine, increased swelling)

Preterm birth (baby born prior to 37 weeks)

C-section
Women with preexisting diabetes (both type 1 and 2), with uncontrolled or untreated high
blood sugar levels have increased chance of (CDC, 2012):
Gestational Diabetes 3

Miscarriage

Preterm birth

Stillbirth

C-section
Women with preexisting diabetes with uncontrolled or untreated high blood sugar levels
can worsen health problems (CDC, 2012):

High blood pressure

Preeclampsia

Kidney disease

Nerve damage

Heart disease

Blindness
Gestational diabetes causes the pancreas to produce an excessive amount of insulin, but
blood glucose levels do not lower. Insulin does not cross into the placenta, but glucose and
nutrients are able to pass (ADA, n.d.). The excess glucose increases the babies blood glucose
levels, causing the baby to produce extra insulin. All the excess energy production leads to fat
storage, which can cause a large baby.
The term for a large baby associated with GDM is macrosomia, or "fat" baby. GDM can
cause the baby to grow to almost 9 pounds or more, which may lead to problems during delivery.
It can be difficult for the baby to be born through the birth canal and possible nerve damage to
the shoulder during birth. There are also risks of newborns with very low blood glucose levels
and possible breathing problems (ADA, n.d.). A very large baby has an increased chance of
being overweight later in life, which in turn can lead to an increased risk of diabetes later in life
Gestational Diabetes 4
(CDC, 2012). Immediately after pregnancy, 5-10% of women with gestational diabetes are found
to have diabetes, usually type 2 (CDC, 2014). Women who have had gestational diabetes have a
35-60% chance of developing diabetes in the next 10-20 years (CDC, 2014).
Women with type 1 or 2 diabetes that has uncontrolled or untreated high blood sugar can
cause her baby to risk having certain health problems (CDC, 2012):

Birth defects (brain, spine, heart especially)

Increased birth weight

Nerve damage to shoulder during delivery

Low blood sugar after birth

Increased chance of overweight, obesity, and/or diabetes later in life
At a woman's first prenatal visit, a risk assessment for GDM should be performed. If
clinical characteristics indicate high risk of GDM, then glucose testing is the next step (discussed
below). High risk for GDM is marked by obesity, personal history of GDM, glycosuria, or
strong family history of diabetes (ADA, 2003). If the initial screening indicated no overt
diabetes, those with an average risk for GDM, should be retested between 24 to 28 weeks of
gestation. Those considered part of the low risk category may not need the screening, but must
fall within the following parameters (ADA, 2003):

Greater than 25 years of age

Normal weight before pregnancy

Low prevalence GDM ethnicity group member including:

No known family history of diabetes

No personal history of abnormal glucose tolerance

No history of poor obstetric outcome
Gestational Diabetes 5
According to the Hyperglycemia and Adverse Pregnancy Outcome (HAPO) study, "the
risk of adverse maternal, fetal, and neonatal outcomes continuously increased as a function of
maternal glycemia at 23-28 weeks, even within ranges previously considered normal for
pregnancy" (ADA, 2014). The results of this study led to the American Diabetes Association to
reevaluate the diagnostic criteria for GDM in their 2014 Standards of Care review (ADA, 2014).
GDM screening can be achieved through one of two strategies (ADA, 2014):

One step: 2 hour, 75 g oral glucose tolerance test (OGTT)

Two step: 1 hour, 50 g (non-fasting) screen followed by a 3 hour, 100 g
OGTT for positive screens
For the "one step" method, OGTT should be performed after an 8 hour overnight fast.
Plasma glucose measurement taken at fasting, 1 hour and 2 hour. GDM is diagnosed when
plasma glucose values exceed (ADA, 2014):

Fasting: ≥ 92 mg/dL

1 hour: ≥ 180 mg/dL

2 hours: ≥ 152 mg/dL
The "two step" method involves plasma glucose measurement at 1 hour, this is step 1. If
in step 1 the plasma glucose level is measured to be ≥ 140 mg/dL, then step 2 is performed. Step
2 should be performed while fasting and plasma glucose levels are measured at fasting, 1 hour, 2
hours, and 3 hours after OGTT. GDM is diagnosed when plasma glucose values meet or exceed
(values based on National Diabetes Data Group criteria) (ADA, 2014):

Fasting: ≥ 105 mg/dL

1 hour: ≥ 190 mg/dL
Gestational Diabetes 6

2 hours: ≥ 165 mg/dL

3 hours: ≥ 145 mg/dL
Women with GDM and a history of GDM should also be screened for persistent diabetes
at 6-12 weeks postpartum, using the OGTT and nonpregnancy diagnositc criteria (ADA, 2014).
The one step method was introduced for all women not known to have prior diabetes in
the 2011Standards of Care after a consensus meeting of the International Association of Diabetes
and Pregnancy Study Groups (IADPSG) (ADA, 2014). The measurements produced an odds
ratio for adverse outcomes of 1.75 when compared to women with the mean glucose level in the
HAPO study (ADA, 2014). This increased the prevalence of GDM from 5-6% to 15-20% due to
only one abnormal value leading to diagnosis, rather than two abnormal values (ADA, 2014).
While there is a higher prevalence of GDM with this one step method, 80-90% of women could
be managed with lifestyle changes (ADA, 2014).
Since the IADPSG recommendation, the National Institutes of Health recommends
continuing the two step method. This recommendation was brought upon by two things: lack of
clinical trial interventions demonstrating benefits of the one step method and possible negative
consequences of identifying a large new group of women with GDM (ADA, 2014).
Certain racial and ethnic groups are especially at risk for developing diabetes (CDC
groups, 2014): African Americans, Hispanic/Latino Americans, American Indians, Asian
Americans, Pacific Islander Americans. Cultural attitudes and behaviors also present barriers to
preventative and management for diabetes care. Minority groups often lack access to proper
health care treatment and are less educated on maternal health. These factors lead to increased
Gestational Diabetes 7
risk for gestational diabetes and complications. Obese women are also at an increased risk of not
only type 2 diabetes, but gestational diabetes that can lead to type 2 diabetes after delivery.
Ethical considerations are focused on the diagnosis of type 2 diabetes or GDM. Some
GDM cases may be representative of preexisting undiagnosed type 2 diabetes (ADA, 2014).
With the increase in obesity of women in childbearing age, screening is warranted for type 2
diabetes at initial prenatal visit. Although, if initial screening determines high risk, overt type 2
diabetes should be tested rather than GDM (ADA, 2014). Another ethical concern is the cost for
treatment if GDM is diagnosed and the burden of knowledge brought on by diagnosis.
Minorities and those with little to no access to health care may find it difficult to afford
medications if lifestyle modifications do not lower risk. The education required presents a
problem for those that are unaware of the necessary lifestyle modifications.
Recommendations:
In screening for GDM, I would recommend the "two step" OGTT. In a study presented
at the annual meeting of the Society for Maternal-Fetal Medicine, the cost effectiveness of GDM
screening using the new IADPSG guidelines showed that while the "two step" method was more
expensive, it proved to be more effective and cost-effective in improving maternal and neonatal
outcomes (Caughey et al, 2012). Another study performed at a teaching hospital found that the
"two step" method, while more expensive to perform, minimized the burden of cost for
individual women and the healthcare system, and provided diagnostic efficacy (Meltzer et al,
2010). There are not as many analyses examining the cost-effectiveness of the balance between
benefits versus the increased costs generated by the "one step" method (ADA, 2014). Most
studies seem to focus on the "two step" method.
Gestational Diabetes 8
To increase screenings, I would informing mothers on the benefits of early detection of
presence of either type 2 diabetes or risk of gestational diabetes. Continuation of the initial
diabetes risk screening is appropriate. Both "one step" and "two step" methods are time
consuming and unpleasant. Upon screening results, obstetricians and gynecologists need to be
prepared to educate patients on benefits of modifying lifestyle choices to stay healthy if
diagnosed with GDM and also, encourage pregnant women to follow up with regular visits to
ensure GDM or type 2 diabetes is under control. Obstetricians and primary care physicians
should stay up to date on screening tests for gestational diabetes. As there is no extensive
evidence as to whether either method is more beneficial than the other.
Public health needs to be very present in screening for GDM. Researchers need to focus
on continuing to study screening tests that are time and cost effective for pregnant mothers and
for large populations. Physicians and obstetricians initially screening for diabetes or those with
high risk for diabetes need to determine the appropriate follow up if results are positive. This
means increased education. Efforts should also be made to increase compensation for GDM
testing.
Almost 1 in 100 women will eventually develop gestational diabetes during pregnancy.
GDM not only causes potential harm to the mother, but to the baby as well. Women are
screened for risk of GDM at initial prenatal visit and then again at 24-28 weeks of gestation.
Two types of GDM screening tests are available: one or two step methods. I would recommend
the "two step" method for screening for GDM due to its cost effectiveness for maternal and
neonatal health.
Gestational Diabetes 9
References
American Diabetes Association. (January 2003). Gestational Diabetes Mellitus. Diabetes Care,
(26). Retrieved from
http://care.diabetesjournals.org/content/26/suppl_1/s103.full.pdf+html
American Diabetes Association. (January 2014). Standards of medical care in diabetes - 2014.
Diabetes Care, (37). Retrieved from
http://care.diabetesjournals.org/content/37/Supplement_1/S14.full.pdf+html
American Diabetes Association (n.d.) What is gestational diabetes? Retrieved from
http://www.diabetes.org/diabetes-basics/gestational/what-is-gestational-diabetes.html
Caughey, A.B.; Cheng, Y.W.; Mission, J.F.; & Ohno, M.S. (October 2012). Gestational diabetes
screening with the new IADPSG guidelines: a cost-effectiveness analysis. American
Journal of Obstetrics & Gynocology, 207(4): 326e1-326.e9. Retrieved from
http://www.ajog.org/article/S0002-9378%2812%2900662-X/fulltext
Centers for Disease Control and Prevention. (2014). 2011 national diabetes fact sheet. Retrieved
from http://www.cdc.gov/diabetes/pubs/estimates11.htm
Centers for Disease Control and Prevention. (2012). Diabetes & pregnancy. Retrieved from
http://www.cdc.gov/features/diabetespregnancy/
Centers for Disease Control and Prevention. (2014). Groups especially affected by diabetes.
Retreived from http://www.cdc.gov/diabetes/consumer/groups.htm
DeSisto, C.L.; Kim, S.Y.; & Sharma, A.J. (2014). Prevalence estimates of gestational diabetes
mellitus in the United States, pregnancy risk assessment monitoring system (PRAMS),
2007-2010. Retrieved from http://www.cdc.gov/pcd/issues/2014/13_0415.htm
Gestational Diabetes 10
Iowa Department of Public Health. (2011). Gestational diabetes and gestational hypertension.
Retrieved from
http://www.idph.state.ia.us/hpcdp/common/pdf/family_health/2011_medicaid_gestational
_diabetes.pdf
Meltzer, S.J.; Morin, L.; Nudi, M.; Penrod, J.R.; & Synder, J. (March 2010). Gestational diabetes
mellitus screening and diagnosis: a prospective randomized controlled trial comparing
costs of one-step and two-step methods. BJOG, 117(4): 407-415. Retrieved from
http://www.ncbi.nlm.nih.gov/pubmed/20105163