Gestational Diabetes – Diagnosis and Management

Detection and management of gestational diabetes reduces birth weight and some maternal adverse outcomes such as pre-eclampsia. Dietary management is the key first step in management.   Risk factors for selection of women to offer OGTT and diagnostic criteria are based on the SIGN guideline. 

• Routine screening at first antenatal visit
• At booking all women should be assessed for the presence of risk factors for gestational diabetes (see table 1).
• All women with risk factors should have HbA1c measured.
• In early pregnancy, levels of HbA1c≥48 mmol/mol, (or fasting glucose ≥7.0mmol/l , or random or two hour glucose after OGTT ≥11.1 mmol/l glucose) are diagnostic of diabetes and these women should be offered treatment pathways as per pre-existing diabetes
• Levels of 42-47mmol/mol should be managed as per GDM pathway
  
  
• Women with previous GDM
• Should have HbA1c and be referred to the diabetes antenatal clinic at booking and offered blood sugar testing aiming pregnancy targets as per established diabetes in pregnancy
• Alternatively a 75 g OGTT can be performed at 10 – 14 weeks gestation

 Routine screening later in pregnancy

• All women with risk factors (see Table 1) - including previous GDM unless already diagnosed or monitoring - should be offered a 75 g OGTT at 24-28 weeks, ideally 24 – 26 weeks.
  
  
• Non- routine screening if
• glycosuria of 2+ or above on 1 occasion
• glycosuria of 1+ or above on 2 or more occasions
• Polyhydramnios
• EFW ≥97th centile
  
  
• Before 35 weeks - measure random glucose and HbA1c and offer 75 g OGTT. If HbA1c ≥42mmol/mol or random glucose ≥11.1mmol in later pregnancy then glucose may be very raised and contact DSN for review before OGTT.
• after 35 weeks
• Offer glucose monitoring for 2-3 days to exclude hyperglycaemia with Diabetes Specialist Nurse

Table 1: Risk factors for gestational diabetes

BMI more than 30 kg/m²
Previous macrosomic baby weighing 4.5 kg or more
Previous gestational diabetes
Family history of diabetes (first degree relative with diabetes)
Previous Pancreatitis
Polycystic Ovarian Syndrome
Age at booking > 35 years
Family origin with a high prevalence of diabetes:

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

SIGN 171 criteria are used for 75 g OGTT:

• fasting venous plasma glucose ≥5.3 mmol/l, OR
• two hours after OGTT ≥9.0 mmol/l.

Women with gestational diabetes should have access to dietary advice from a dietician, advice to undertake moderate exercise for 150 minutes/week as well as consideration of treatment with metformin and/or insulin if needed.

Home blood glucose monitoring before meals and two hours after evening meal, aiming fasting pre-meal glucose < 5.5 mmol/l and 2 hours post-prandial glucose < 7.0 mmol/l.

If blood glucose continues to be above target ≥2 times in 5 days, metformin should be considered, and subsequently insulin if blood glucose continues to be above target despite optimisation of oral therapy.

If insulin is to be used for > 3 months then the woman needs to be advised to inform the DVLA.

Advise women with gestational diabetes to give birth no later than 40+6 weeks, and offer elective birth (by induction of labour, or by Caesarean section if indicated) to women who have not given birth by this time. Consider elective birth before 40+6 weeks for women with gestational diabetes if there are maternal or fetal complications [SIGN 171, 2024].

Women with frank diabetes by non-pregnant criteria (fasting venous glucose ≥7 mmol/l, random or two hour ≥11.1 mmol/l) should be managed within a multidisciplinary clinic as they may have type 1 or type 2 diabetes and be at risk of pregnancy outcomes similar to those of women with pre-gestational diabetes.

Women who have had GDM are at an increased of type 2 diabetes in later life, and should be advised to reduce this risk by weight management, diet and exercise.  

All women should be fasting glucose at 6 weeks (no earlier) post-partum. This can be offered as part of 6 week check.

Access to specialist weight management services is available and women can self refer: NHS Borders Intranet, Weight Management Team

SIGN 171: SIGN 171 Management of diabetes in pregnancy

NICE Diabetes in Pregnancy: Recommendations | Diabetes in pregnancy: management from preconception to the postnatal period | Guidance | NICE

Greater Glasgow and Clyde Guidelines for the Management of Diabetes Mellitus during Pregnancy and Diagnosis of Gestational Diabetes (1136)

Lothian Diabetes and Pregnancy Guideline 2024