Gestational Diabetes

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For the purpose of this guideline Gestational Diabetes Mellitus (GDM) is defined as glucose intolerance occurring in pregnancy which returns to normal after delivery of baby. Around 2 - 5% of women in our population will develop GDM. The International Association of Diabetes and Pregnancy Study Group’s consensus document suggests that all women at high risk should be offered screening with HbA1c, fasting or random glucose at the first gestational visit 1. Highland Health has adopted the recommendations for screening for GDM according to SIGN Guideline 116, 2010 2 .
An important aim of screening, particularly in early pregnancy, is to identify women with undiagnosed type 2 diabetes and those with rarer forms of diabetes such as Maturity Onset Diabetes of the Young (MODY). Clinical suspicion of pre existing diabetes may be raised by persistent heavy (2+) glycosuria in pregnancy on more than 2 occasions, random glucose >5.5 two hours or more after food, or >7.0 within two hours of food.
Randomised control trials have shown that intervention in women with gestational diabetes with dietary advice, monitoring and management of blood glucose is effective in reducing birth weight, and the incidence of large for gestational age infants, and perinatal morbidity 1,3,4,5.
For management of GDM in pregnancy please see the separate guideline NHS Highland Screening, Diagnosis and Management of Gestational Diabetes in Pregnancy.

Risk factors for gestational diabetes
  • Previous history of gestational diabetes.
  • BMI >30.
  • Previous baby weighing 4.5kg or more.
  • Family history of Type 2 or Gestational Diabetes.
  • Ethnicity South Asian, Black Caribbean, Middle Eastern*.
  • A history of Polycystic Ovarian Syndrome.
  • Previous unexplained stillbirth.

* South Asian (specifically women whose country of family origin is India, Pakistan or Bangladesh)
Middle Eastern (specifically women whose country of family origin s Saudi Arabia, United Arab Emirates, Iraq, Jordan, Syria, Oman, Qatar, Kuwait, Lebanon or Egypt)

Screening

At booking all women should be assessed for the presence of risk factors for gestational diabetes.

All women with risk factors (see below) should have screening with HbA1c or fasting glucose if practical. The use of a formal 75g Oral Glucose Tolerance Test (OGTT) is not recommended at gestations of less than 12 weeks.

All women with risk factors should also be screened later in pregnancy between 24 and 28 weeks with a formal 75g OGTT with bloods taken at fasting and 2 hours after the glucose load.

The oral glucose tolerance test can be performed in the community by practice nurses, general practitioners and midwives. Alternatively the test can be performed in the Day Case Unit at Raigmore Hospital or Invergordon.

Additional indications for screening may arise in women who do not have recognised risk factors. These indications include persistent glycosuria, unexplained macrosomia or polyhydramnios. Screening for these women will usually take the form of a 75g OGTT.

Diagnosis criteria for GDM with 75g OGTT

An abnormal OGTT is defined by:

A fasting glucose ≥ 5.1

A 2 hour glucose ≥ 8.5

Those with abnormal results should be referred to the joint Obstetric Diabetes Service at Raigmore Hospital by contacting the Senior Charge Midwife or Diabetes Specialist Nurses.

Editorial Information

Last reviewed: 14 June 2019

Next review: 14 June 2021

Author(s): Diabetes Specialist Nurse

Version: 1

Approved By: TAM Subgroup of ADTC

Reviewer Name(s): Diabetes Specialist Nurse