Gestational Diabetes Mellitus To Screen or Not To Screen

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Gestational Diabetes Mellitus - To Screen or Not
To Screen

• A Review of the SOGC Clinical Practice Guidelines
  (November 2002)

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What is Gestational Diabetes Mellitus (GDM)?

• Affects 3-4 of pregnant population
• Onset or first recognition of diabetes mellitus
  during pregnancy
• Applies whether or not insulin is used or if
  condition persists
• Glucose intolerance may have antedated pregnancy

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Risk Factors for GDM

• Previous Hx of GDM or glucose intolerance
• FHx of DM (esp. 1st degree relative)
• Previous macrosomia (gt4000g)
• Previous unexplained stillbirth
• Previous neonatal hypoglycemia, hypocalcemia, or
  hyperbilirubinemia
• Advanced maternal age

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Risk Factors for GDMcont

• Obesity
• Repeated glycosuria in pregnancy
• Polyhydramnios
• Suspected macrosomia
• Up to 50 have NO RISK FACTORS

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Clinical Value and Benefit of Screening

• Controversial
• Association exists between level of maternal
  hyperglycemia and several maternal-fetal outcomes
• No RCTs to conclusively show that Dx and Tx will
  lead to decrease in immediate and long-term
  effects
• Conflicting evidence exists

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Possible Positive Outcomes of GDM Identification
and Tx

• Decrease in perinatal mortality
• Decrease in macrosomia and shoulder dystocia
• Reduction in preeclampsia
• Reduction in C-section rate
• Reduction in brachial plexus injury

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Possible Positive Outcomes of GDM Identification
and Tx

• Reduction in immediate neonatal metabolic
  complications related to maternal hyperglycemia
• Prevention of long-term effects of GDM on child
  and mother

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Results of Screening Based on Current Evidence

• Decrease in macrosomia
• Increase in C-section rate due to identification
  of GDM
• No evidence for other health benefits for child
  or mother
• Large prospective RCT needed

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Results of Screening

• Evidence that identification of GDM may result in
  unfavorable maternal outcomes
• Hunter and Keirse except for research purposes
  all forms of glucose tolerance testing should be
  stopped (Effective Care in Pregnancy and
  Childbirth)

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Universal vs. Selective Screening

• Universal screening common
• Selective screening of those with risk factors
  suggested to reduce burden
• Sensitivity 63 and specificity 56
• 37 to 50 go undiagnosed

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Universal vs. Selective Screening

• Prior to 1995 universal screening recommended b/c
  of low sensitivity
• Recent data suggests no screening if lt25,
  caucasian and not obese
• 90 still screened
• Universal screening still popular

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History of Screening for GDM

• 1992 Canadian Task Force on the Periodic Health
  Examination - insufficient evidence to recommend
  screening
• 1992 SOGC - Universal
• 1997 Fourth International Workshop/Conference on
  GDM - Selective

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History of Screening for GDMcont

• 1998 CDA - Selective
• 1998 ADA - Selective
• 2001 ACOG - Universal or selective

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Current Screening Practices

• Canada - universal screening practiced by 84 of
  Obstetricians
• USA - universal screening standard for 94-97 of
  obstetricians
• UK - 17 practice universal screening, 11 do not
  screen, 72 screen if risk factors

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Suggested Screening Alternatives

• Screening with glucose challenge test followed by
  oral glucose tolerance test
• Screening with 75g OGTT
• Random blood glucose or fasting blood glucose

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Diagnostic Criteria for GDM

• Based on the 1998 Clinical Practice Guidelines
  for the Management of Diabetes in Canada
• Fasting plasma glucose gt7.0 mmol/L or random
  plasma glucose of gt 11.1mmol/L
• 75g OGTT FPG ? 5.3 mmol/L, PG 1 Hour ?10.6, PG
  2 hour ? 8.9
• GDM2abnormal values, IGTone abnormal value

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Diagnostic Criteria for GDM

• 100g OGTT FPG?5.3, 1 hour PG ?10.0, 2 hour PG
  ?8.6, 3 hour PG ? 7.8
• 2 or more values must be met or exceeded
• Should be performed after 8-14h fast and after 3
  days of unrestricted diet
• Postpartum - test after 6-12 weeks

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Recommendations - Summary

• Not enough evidence to prove benefits of large
  screening program
• Recommendations based on consensus or expert
  opinion
• The following practices are acceptable...

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Recommendations

• Routine screening at 24-28 weeks GA with 50g GCT
  using threshold of 7.8 mmol/L, except low risk
  patients
• Dx test can be 100g OGTT (ACOG) or 75g OGTT (ADA)
• Option of not screening for GDM acceptable
• No data to stop screening if practiced

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Recommendationscont

• High risk should undergo Dx test early in
  pregnancy and should be repeated at 24-28 weeks
  if initial results negative
• If GDM Dx, reassess with a 75g OGTT 6-12 weeks
  postpartum to identify glucose intolerance

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Recommendationscont

• Large RCT needed to determine if identification
  and management of GDM is associated with
  significant improvement in neonatal and maternal
  outcome
• No such study is yet underway
• Need universally-accepted, outcome-based Dx
  criteria for GDM