Gestational Diabetes Quick Facts
PB180
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Early
Screening – recommended in overweight and obese women with
additional risk factors (can use either 50g or 75g…but if
75g, just do the fasting and 2-hour values)
o
Risk factors = physical inactivity, 1st
degree relative with DM, high-risk race/ethnicity, prior
infant >4000g, prior GDM, HTN (140/90 or tx), HDL <35,
triglycerides >250, PCOS,
prior A1c 5.7% or
higher (or other test showing impaired glucose tolerance),
BMI 40+, acanthosis nigricans, h/o cardiovascular disease
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Routine
Screening – all pregnant women between 24-28 weeks gestation
(use the 50g for screening…cutoffs of 130, 135 and 140 are
all acceptable)
o
If 50g
is abnormal, then proceed with diagnostic 100g…traditionally
required 2 elevated values for dx, but also acceptable to
use 1 elevated value for dx
o
We use the Carpenter Coustan cut-offs of 95-180-155-140
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Repeat Screening – women with an abnormal
screening test but normal diagnostic test in the 1st
trimester should have repeat testing at 24-28 weeks (okay to
skip directly to 3h diagnostic test)
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Blood Glucose Monitoring – should be done 4x/day (at least
until control is proven), should be reviewed weekly by
physician (more or less frequently depending on control)
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Fasting: goal <95
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Post-prandial: can do 1-hour (goal <140) or 2-hour (goal
<120), neither is superior
Risks of Gestational Diabetes
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Maternal: hypertensive disorders, C/S, DM later in life
(70% will develop GDM w/in 20-30y)
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Fetal: macrosomia, hypoglycemia, hyperbilirubinemia,
shoulder dystocia, birth trauma, stillbirth
Benefits of Treatment: reductions in preeclampsia/HTN
disorders, LGA, C/S, shoulder dystocia
Treatment Modalities
1.
Diet – the ADA recommends registered dietician counseling
and development of a personalized nutrition plan based on
BMI for all pts with GDM…three major components
a.
Caloric
allotment
b.
Carbohydrate intake – 40% carbs, 40% fat, 20% protein
c.
Caloric
distribution – 3 meals and 2-3 snacks
2.
Exercise – 30 minutes of moderate intensity aerobic
exercise at least 5 days/week, walking 10-15 minutes after
each meal
3.
Insulin – standard therapy for GDM refractory to
diet/exercise as per ADA, typically started at 0.7-1.0
units/kg/day
a.
NPH is
the preferred long-acting agent. Onset 1-3h, peak 5-7h,
duration 13-18h.
b.
Lispro/Aspart are preferred short-acting agents. Onset
1-15m, peak 1-2h, duration 4-5h.
4.
Oral Diabetes Medications – not FDA
approved for GDM and considered 2nd
line by ADA
a.
Metformin – a biguanide, inhibits hepatic gluconeogenesis
and glucose absorption, also stimulates glucose uptake in
the periphery
i.
Advantages: equivalent glycemic control and outcomes
compared to insulin
ii.
Disadvantages: crosses the placenta with unknown long-term
consequences, may increase risk of preterm labor
b.
Glyburide – a sulfonylurea, binds to pancreatic cells to
increase insulin secretion, also increases insulin
sensitivity in the periphery
i.
Advantages: none
ii.
Disadvantages: worse neonatal outcomes (despite equivalent
glycemic control compared to insulin), crosses the placenta
with unknown long-term effects
Fetal Surveillance – typically started at 32 weeks is women
with poorly-controlled GDM or GDM requiring medication,
specific test and frequency of testing is unknown although
testing that incorporates amniotic fluid measurements in
probably better given that GDM is associated with
polyhydramnios (there is no consensus re: surveillance in
women with well-controlled A1GDM)
Ultrasound – “reasonable for clinicians to assess fetal
growth by ultrasonography” in an attempt to identify
macrosomia, although only ~22% of fetuses identified as
macrosomic on US will actually be LGA at birth AND most
cases of macrosomia aren’t severe enough to alter delivery
planning
Delivery Timing – elective C/S counseling only if EFW
is >4500 grams
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Well-controlled A1GDM: delivery between 39 0/7 – 40 6/7
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Well-controlled A2GDM: delivery between 39 0/7 – 39 6/7
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Poorly-controlled GDM: delivery between 37 0/7 – 38 6/7
(earlier only if inpatient attempts to improve glycemic
control have failed or if antepartum testing is abnormal)
Postpartum Management – screen for diabetes at 4-12 weeks
post-partum with a 75g 2-hour OGTT
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Normal = fasting <100 and 2h <140
o
Lifestyle counseling, retest every 1-3 years
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Impaired = fasting 100-125 or 2h 140-199
o
Lifestyle counseling, consider referral for management,
consider Metformin if both values abnormal, retest every 1
year
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Diabetes = fasting >125 or 2h >200
o
Refer for management
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