It is well known that raised glucose levels in women with established
diabetes increase both morbidity and mortality among their offspring
due mainly to an increased incidence of congenital abnormalities and
excessive fetal growth in the third trimester. Whether milder elevations
of maternal glucose are clinically relevant in pregnancy has been controversial.
However, emerging evidence points to a linear increase in fetal
risk as maternal glucose concentrations rise. Much of this morbidity
can be prevented with aggressive treatment of hyperglycaemia, often
with insulin. Furthermore, transient glucose intolerance in pregnancy has
major implications for the women affected, since it confers a risk of
type 2 diabetes in later life which exceeds 50%. It is therefore now
established that gestational diabetes mellitus is of considerable clinical
relevance. Obstetric units should establish clear policies to ensure that
those at risk are reliably identified, appropriately treated during pregnancy
and then equipped to make the necessary lifestyle changes to try
and prevent them developing diabetes in later life.
Introduction
Epidemiology
Criteria currently used to define gestational diabetes
WHO One or more values following
a 75 g glucose load; fasting
plasma glucose ≥7 mmol/L, 2-h
glucose ≥7.8 mmol/L
EASD One or more values following
a 75 g glucose load; fasting
plasma glucose ≥6 mmol/L, 2-h
glucose ≥9 mmol/L
ADA Two or more values following
a 100 g glucose load; fasting
plasma glucose ≥5.3 mmol/L,
1-h glucose ≥10 mmol/L, 2-h
glucose ≥8.6 mmol/L, 3-h
glucose ≥7.7 mmol
Traditional risk factors associated with gestational
diabetes
Maternal BMI
Maternal age
Polycystic ovarian syndrome
Increasing maternal parity
Previous gestational diabetes
Family history of diabetes
Previous stillbirth
Previous congenital abnormality
Twin pregnancy
Pathogenesis
How should screening be performed?
Congenital malformations in gestational diabetes
Fetal macrosomia
Timing of delivery in gestational diabetes
Future risks of type 2 diabetes
Conclusion
Despite the uncertainty relating to the value of screening and
treatment of mild GDM in the past, it now seems clear that this
is a disorder with serious adverse perinatal outcomes but which
is responsive to treatment, and therefore that screening for the
condition is justified. It is also clear that screening for GDM will
identify a group of women who are at increased risk of type 2
diabetes later in their lives and that exciting developments in prophylaxis of type 2 diabetes may be applied with a major long term health benefit.
