This document discusses screening and diagnosis of gestational diabetes mellitus (GDM). It begins by outlining the learning objectives and explaining why screening for GDM is important. It then discusses different screening protocols including risk-based versus universal screening, timing of screening, and recommended screening tests. The document reviews diagnostic criteria from organizations like the IADPSG and DIPSI and presents case studies applying these criteria. It also discusses implications of pre-existing diabetes in pregnancy like congenital malformations and maternal complications. In summary, the document provides an overview of guidelines and considerations for screening and diagnosing GDM.

1. SCREENING AND DIAGNOSIS
OF GDM
1
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2. Learning Objectives
• Learn about the different screening & diagnostic
protocols for GDM
• Appreciate the differences between GDM and
pre-existing diabetes in pregnancy and their impact
2
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3. SCREENING FOR GDM
3
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4. SCREENING FOR GDM
Key questions:
• Why screen
• Whom to screen
• When to screen
• How to screen
4
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5. SCREENING FOR GDM
Why screen?
• High prevalence of GDM and diabetes in India
• Early diagnosis & treatment improves fetal and maternal
outcomes
• Risk reduction for future maternal diabetes
• Risk identification for diabetes in offspring
• Reduction of trans - generational transmission of diabetes
5
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6. Case Study 1
Mrs. S is a 35 year old nulliparous lady with a bad obstetric history, having
had two miscarriages in the last three years.
She has never tested her blood glucose levels during either of her previous
pregnancies.
Her mother has diabetes.
• Does she need to be screened for diabetes?
• If so, when?
• What screening test is to be used?
6
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7. Case Study 2
Mrs. A is a 22 year old primigravida coming for her first antenatal checkup
at 12 weeks of gestation.
On examination, she is 152 cm tall and weighs 54 kg. Her BMI is 23.3 kg/m2.
She does not have a family history of diabetes.
• Does she need to be screened for diabetes?
• If so, when?
• What screening test is to be used?
7
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8. SCREENING FOR GDM
Whom to screen?
• Selective screening
• Universal screening
8
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Contd…

9. SCREENING FOR GDM
High Risk Approach
The ADA recommends that women “at low risk” for GDM need not be
screened i.e.
 Age <25 years
 Normal weight before pregnancy
 Member of ethnic group with low diabetes prevalence
 No diabetes in first degree relatives
 No history of abnormal glucose tolerance
 No history of poor obstetric outcome
However, the guideline also appreciates that very few women will fall into
this category
9
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Contd…

10. SCREENING FOR GDM
Universal Approach
Asian Indians are a high risk ethnic group for development of
diabetes.
Hence all pregnant Indian women need to be screened for GDM
DIPSI Guidelines, J Assoc Physicians India, 2006
10
Contd…
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This is consistent with the Indian National Guidelines

11. SCREENING FOR GDM
When to screen
• GDM usually develops during late pregnancy (after the first
trimester)
• However, if screening is delayed till that time, there is a
chance that pre-existing diabetes may be missed
• Therefore it is ideal to perform the first screening as early as
possible (during the first antenatal checkup)
11
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Contd…

12. SCREENING FOR GDM
When to screen
• ADA- as early as possible in pregnancy; if negative, retest
between 24 to 28 weeks
• DIPSI - first screening at the first visit (if negative repeat
at 24 to 28 weeks and then at 32 to 34 weeks)
12
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Contd…

13. SCREENING FOR GDM
What test to use?
The 75 g oral glucose tolerance test (OGTT) is the gold
standard for screening and diagnosis of GDM and has
gained international acceptance.
13
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Contd…

14. DIAGNOSIS OF GDM
14
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15. DIAGNOSIS OF GDM
• There are no universally accepted diagnostic criteria for GDM
• Traditionally, the criteria put forward by Carpenter and
Coustan (modified O’Sullivan - Mahan criteria) and WHO
(1999) have been used
• Based on the results of the Hyperglycemia and Adverse
Pregnancy Outcomes (HAPO) study, the International
Association of Diabetes in Pregnancy Study Groups (IADPSG)
has published guidelines on diagnosis of GDM, which are
outcome based and have gained widespread acceptance
15
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16. IADPSG GUIDELINES
Two Components
1. Detection of overt, hitherto undiagnosed diabetes during
early pregnancy using accepted clinical criteria
2. Diagnosis of GDM in later pregnancy using OGTT
16
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17. IADPSG GUIDELINES
1. Detection of Overt Diabetes
• To be performed at the initial antenatal visit
• FPG, HbA1c or random glucose can be used
• If results suggestive of overt diabetes (FPG ≥ 126 mg/dl;
HbA1c ≥ 6.5% or random glucose≥200 mg/dl with symptoms
of hyperglycemia), start treatment
• If results not suggestive of overt diabetes
 And FPG between 92 and 125 mg/dl, diagnose GDM
 And FPG <92 mg/dl, repeat screening at 24 to 28 weeks
IADPSG, Diabetes Care, 2010
17
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18. IADPSG GUIDELINES
2. Screening for GDM
• Performed at 24 to 28 weeks of gestation
• 75 g, two hour OGTT used
• If FPG ≥ 126 mg/dl, overt diabetes is diagnosed
• If FPG <126 mg/dl, GDM is diagnosed if any one of the
values exceeds the thresholds shown below
Fasting 1 hour 2 hour
Plasma Glucose
(mg/dl)
≥92 ≥180 ≥153
IADPSG, Diabetes Care, 2010
18
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The WHO recommends that the diagnosis of pre-existing (overt)
diabetes can be made if the 2-hour value is ≥200 mg/dl
WHO, 2019

19. Case Study 3
Mrs. K, a 24 year old primigravida, is screened for diabetes during the
15th week of gestation.
Her results are as follows.
Fasting plasma glucose= 79 mg/dl
HbA1c= 4.9%
• Does she have diabetes?
• Does she need to be retested for diabetes?
• If so, when and using what test?
19
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20. Case Study 3 (Cont.)
Mrs. K undergoes an OGTT with 75 g of glucose at 25 weeks’ gestation.
Her results are as follows.
What is the diagnosis?
Time 0 hr (Fasting) 1 hour 2 hour
Glucose (mg/dl) 90 176 159
20
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21. DIAGNOSIS OF GDM
Merit of IADPSG Guidelines
As of today, IADPSG criteria are the only guidelines based on
pregnancy outcome data as revealed by the HAPO study
So let’s look at the outcome data now.
21
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22. THE HAPO STUDY
• Looked at whether maternal hyperglycemia less severe than
that diagnostic of diabetes mellitus was associated with
adverse pregnancy outcomes
• Studied >25,000 pregnant women from 9 countries from 24 to
32 weeks onwards
• Women with glucose levels not suggestive of diabetes by
OGTT were included
The HAPO Study Cooperative Research Group, N Engl J Med, 2008
22
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23. THE HAPO STUDY
Results
There was a continuous strong association between maternal
glucose levels below those diagnostic of diabetes and adverse
outcomes
23
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24. THE HAPO STUDY Results
The HAPO Study Cooperative Research Group , N Engl J Med, 2008
24
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25. IADPSG GUIDELINES
Pros and Cons
Pros
• The first guideline to be developed based on pregnancy outcomes
Cons
• Only one abnormal value is required for diagnosis. This may lead to
overdiagnosis of GDM mainly due to low plasma fasting glucose cut
off of 92 mg/dl
• May be difficult to perform three blood samples in resource poor
settings like India.
25
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26. IADPSG GUIDELINES-Present Status
These guidelines have been accepted by
• American Diabetes Association
• World Health Organisation
• Endocrine Society
• Australian Diabetes in Pregnancy Society (ADIPS) and
• International Federation of Gynecology and Obstetrics (FIGO)
26
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27. DIAGNOSIS OF GDM
The DIPSI Criteria
• 75 g glucose load
• Sample collected at 2 hours
• A value of ≥ 140 mg/dl is diagnostic of GDM
Seshiah V, J Assoc Physicians India, 2007
27
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The DIPSI guidelines state that the OGTT can also be
administered in the non-fasting state. However, recent studies
have shown conflicting results on its sensitivity and specificity
vis-à-vis the fasting OGTT
Mohan et al, Acta Diabetol, 2015
Vij et al, Int J Diabetes Dev Ctries, 2015
Herath et al, Int Archiv Med, 2015

28. Case Study 4
Diagnosis of GDM using DIPSI criteria
Mrs. C, a 25 year old primigravida, underwent a screening oral glucose
tolerance test (OGTT) with 75 g glucose at 14 weeks’ gestation.
Her results are as follows.
• Does she have diabetes?
• Does she need to be tested again?
• If so, when?
Time 0 hr (Fasting) 2 hour
Glucose (mg/dl) 86 137
28
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29. Case Study 4 (Cont.)
Diagnosis of GDM using DIPSI criteria
Mrs. C undergoes repeat testing at 26 weeks’ gestation.
Her results are as follows.
Does she have GDM?
Time 0 hr (Fasting) 2 hour
Glucose (mg/dl) 88 161
29
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30. PROPOSED GUIDELINES FOR SCREENING FOR GDM
IN INDIA
Source : Modified from Mohan V, Usha
S, Uma R. J Postgrad Med
2015;61:151-4
Slide 30
or

31. • Ideally, and whenever feasible, a single step 75g OGTT using
the IADPSG criteria should be done in the fasting state
• However, in resource limited settings, especially in the rural
areas of developing countries where getting all pregnant
women to come in a fasting state may be difficult, 75g DIPSI
criteria in the non-fasting state can be utilised. Clinicians
should be aware that the sensitivity of this test has not been
unequivocally proven and therefore there is a risk of women
with GDM being missed out
CONCLUSIONS REGARDING SCREENING
FOR GDM
Slide 31

32. PRE-EXISTING DIABETES
AND PREGNANCY
32
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33. Case Study 5
Mrs. C, a 32 year old primigravida, reports for the first antenatal checkup.
She is obese with a body mass index of 35 kg/m2. Both her parents have
diabetes.
Her fasting plasma glucose is 192 mg/dl.
Her HbA1c is 9.2%.
• What type of diabetes does this patient have?
• What is the prognosis for the pregnancy and for future resolution of
diabetes?
33
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34. PRE-EXISTING DIABETES
AND PREGNANCY
• Clinically distinct from GDM
• Type 2 diabetes complicating pregnancy is becoming
more frequent nowadays, due to younger age of onset of
type 2 diabetes in India
• Women with long duration of pre-existing diabetes may
have damaged vasculature even before they become
pregnant
34
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35. IMPLICATIONS OF PRE-EXISTING DIABETES
The Concept of Fuel Mediated Teratogenesis
Preconceptional diabetes (of any type) has more serious implications for
the fetus than GDM, since the former can influence fetal development
periconceptionally as well as throughout pregnancy
35
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Modified from Freinkel, Diabetes, 1980

36. CONGENITAL MALFORMATIONS
Possible Etiologies
• Both environmental and genetic factors are implicated
• The main maternal teratogenic factors are hyperglycemia and
hyperketonemia
36
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37. CONGENITAL MALFORMATIONS
37
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Contd…
Central nervous system:
• Neural tube defects (meningocele, encephalocele, anencephaly)
• Caudal regression syndrome
• Holoprosencephaly
Cardiovascular system:
• Tetralogy of Fallot
• Transposition of great vessels
• Left-sided obstructive lesions (hypoplastic left heart syndrome,
aortic stenosis, coarctation)
Genitourinary system:
• Renal agenesis
• Hydronephrosis
• Ureteral duplication
• Cystic kidneys

38. CONGENITAL MALFORMATIONS
38
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Gastrointestinal system
• Duodenal atresia
• Anorectal atresia
Musculoskeletal system
• Arthrogryposis
• Hypoplastic femur
Functional
• Intraventricular septal hypertrophy
• Small left colon syndrome
While Neural Tube Defects (NTDs) are the commonest congenital anomaly in
Infants of diabetic mothers, they are not specific for diabetes. The most specific
anomaly is sacral agenesis (Caudal regression syndrome), but this is rare

39. Anomaly Timing (weeks of gestation)
Skeletal
Caudal regression
Spina bifida
3
6
Neural
Anencephaly
Myelocele
Hydrocephalus
4
4
5
Cardiovascular
Dextrocardia
Conus arteriosus defects
Ventricular septal defect
4
5
6
Renal
Renal agenesis/ hypoplasia 6
TIMING OF CONGENITAL MALFORMATIONS
39
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40. Malformation Ratio of incidence (Diabetic vs control)
Caudal regression 252
Situs inversus 84
Ureter duplex 23
Renal agenesis 5
Cystic kidney 4
Cardiac anomalies 4
Anal/ rectal atresia 3
Anencephaly 3
Spina bifida and other CNS anomalies 2
CONGENITAL MALFORMATIONS IN INFANTS OF DIABETIC MOTHERS
Gardner DG, Shoback D (eds). Greenspan’s Basic and Clinical Endocrinology, 10th edn, 2018
40
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41. NEURAL TUBE DEFECTS
Most common but nonspecific manifestation of diabetic embryopathy; routine
periconceptional folate supplementation of pregnant women has drastically reduced the
incidence in non-diabetic pregnancies but its benefits in diabetes are not as clear.
Nevertheless, all pregnant women with diabetes should be advised folate
supplementation
41
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Pic courtesy: Dr. V. K. Abichandani, Ahmedabad

42. SACRAL AGENESIS
(CAUDAL REGRESSION SYNDROME)
Most specific but rare manifestation of diabetic embryopathy
Plain x-ray pelvis showing absence
of sacral segments (arrow)
Shortened spine with absence
of sacral segments
42
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43. SACRAL AGENESIS
(CAUDAL REGRESSION SYNDROME)
Fetus expelled at 14 weeks showing absence of sacrum and lumbar spine
Pics courtesy Drs. P. Suresh Kumar and Jeena Baburaj, Calicut
43
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44. STRUCTURAL ANOMALIES AND PERICONCEPTIONAL HbA1C
44
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Guerin A et al, Diabetes Care, 2007
• High HbA1c is not an indication in itself for terminating the pregnancy
• The pregnancy and neonatal risks associated with high HbA1c should be discussed
and proper counseling offered

45. CONGENITAL MALFORMATIONS
• In pre- existing diabetes, congenital malformations remain a
major cause for pregnancy loss*
• Severe malformations cause early pregnancy loss
• Fetal metabolic acidosis with or without hypoxemia is an
additional factor in late fetal loss**
45
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*Rackham et al, Postgrad Med J, 2009
**Silver et al, Am J Obstetr Gynecol, 2007

46. MATERNAL DIABETES COMPLICATIONS
Diabetic Retinopathy
• Diabetic retinopathy can worsen during pregnancy
• Postulated mechanisms include alterations in levels of hormones
like HPL, estrogen and progesterone, increased cardiac output
leading to increased retinal blood flow and concomitant
hypertension
• Improvement of glycemic control before or during pregnancy can
paradoxically worsen retinopathy
• Some authors have noted a correlation between severity of
retinopathy and adverse perinatal outcomes*
*Klein et al, J Diabet Complications, 1988
46
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Contd…

47. DIABETIC RETINOPATHY IN PREGNANCY
Retinal photographs showing worsening of retinopathy following
pregnancy in a woman with type 1 diabetes
47
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48. MATERNAL DIABETES COMPLICATIONS
Diabetic Retinopathy
Risk factors for worsening of retinopathy include
• Non-modifiable
 Duration of diabetes
 Severity of retinopathy prior to pregnancy
 Poor glycemic control before conception
• Modifiable
 Chronic or pregnancy induced hypertension
 Rapid normalisation of blood glucose
 Anemia
48
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Contd…

49. • If retinopathy is present prior to pregnancy, it needs to be
frequently monitored throughout the pregnancy
• If sight threatening retinopathy is present, laser
photocoagulation or other treatment should be
completed before or early in the pregnancy.
MATERNAL DIABETES COMPLICATIONS
Diabetic Retinopathy
49
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50. MATERNAL DIABETES COMPLICATIONS
Diabetic Nephropathy
• In women with reduced creatinine clearance, there is an
increased risk of deterioration of renal function during
pregnancy
• Pregnancy does not accelerate deterioration in renal function
in women with normal creatinine clearance
50
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Contd…

51. MATERNAL DIABETES COMPLICATIONS
Diabetic Nephropathy
Diabetic nephropathy can significantly affect pregnancy outcome
due to
• Increased risk of maternal hypertensive complications
• Increased risk of preterm delivery due to deteriorating
maternal BP and pre-eclampsia
• Increased risk of fetal growth restriction and fetal distress due
to placental insufficiency
51
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52. TAKE HOME MESSAGES
• All pregnant women in India should be screened for diabetes
• First screening should take place at the first antenatal visit
• Pre-existing diabetes in a pregnant woman has more serious
implications than GDM, both for the mother as well as the
fetus
• There are a number of screening and diagnostic criteria for
GDM; depending on the clinical setting and the availability of
resources, the appropriate criteria may be used.
52
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53. • Wherever possible IADPSG criteria should be used to
diagnose GDM
• However, in situations where all pregnant women cannot
be referred in the fasting state for a diagnostic OGTT, the
DIPSI non-fasting test can be done.
TAKE HOME MESSAGES
53
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54. The Oral Glucose Tolerance Test (OGTT)
Standard Procedure (Modified form WHO, 1999)
• Test preceded by > days of normal, unrestricted diet (>150 g
carbohydrate daily) with normal physical activity.
• Carbohydrate-rich meal (30-50 g) on night before test.
• Overnight fast of 8-14 hours; only water may be ingested
• Record any factors that may affect interpretation of test, such
as medication, inactivity, infection, gestation of pregnancy,
acute psychological stress, etc.
54
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55. The Oral Glucose Tolerance Test (OGTT)
Standard Procedure (Modified form WHO, 1999)
• Collect fasting (and all other) samples in tube that permits measurement
of plasma glucose (e.g. sodium fluoride tube).
• Timing of test (0 hours) starts at beginning of glucose drink.
• Adults ingest 75 g anhydrous glucose (100 g in case of the Carpenter -
Coustan OGTT) or 82.5 g of glucose monohydrate in 250-300 ml water
over 5 minutes.
• No smoking during test.
• Take blood sample at 1 and 2 hours (in case IADPSG criteria are being
used) or at 1, 2 and 3 hours (if Carpenter- Coustan criteria are used)
55
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56. The Oral Glucose Tolerance Test (OGTT)
Standard Procedure (Modified form WHO, 1999)
• Ideally take sample from warmed vein on back of hand (antecubital fossa
samples may be artificially lower).
• An indwelling butterfly or conventional cannula can be left in situ
throughout the test (affix in place and dress); flush with saline after taking
fasting sample, then draw at least 10 ml and discard before drawing
sample for assay tube.
• Glucose should be measured immediately after collection by near-patient
testing or, if a blood sample for a laboratory is collected, plasma should be
immediately separated, or the sample should be collected into a container
with glycolytic inhibitors and placed in ice-water until separated prior to
analysis.
56
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57. PRIMER TO MODULE III
57
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58. Module III
Management of Diabetes in Pregnancy (Part I)
• Pre - conception counselling
• Need for treating GDM
• Management of GDM
58
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