Gestational Diabetes Mellitus (GDM)
· = Any degree of glucose intolerance with onset or first recognition during pregnancy
· For most it consists of mild glucose intolerance manifest during the 2nd or 3rd trimester and normalising following delivery
· Affects 4 – 8 % of all pregnancies (Indian women >> than European). Risk factors:
o Maternal age > 35 years
o Family history of diabetes
o Previous macrosomia, unexplained still birth
o Glycosuria on two or more separate occasions. 20% of women have glucose in their urine Þ not a reliable indicator
· Associated with:
o Morbidity for mother – 1.5 times risk of caesarean delivery
o Increased risk of type 2 diabetes in the mother (up to 50% over next 10 years). ?Would have got it anyway. Also hypertension, hyperlipidaemia, etc.
o 2.5 times morbidity for baby, including:
§ Large for gestational age, macrosomia (birth weight > 4000 gm – but most macrosomic babies‟ mothers have normal glucose tolerance)
§ Risk of inter-uterine fetal death (IUFD)
§ Possibly neonatal jaundice, polycythaemia, post-natal hypoglycaemia, prematurity – but not congenital malformations (unless IDDM mother)
o But in general risks are low
· Is usually asymptomatic (ie no polyuria and thirst). Risk factors have low predictive power Þ universal screening usual
· NZ guidelines:
o All women should be tested for glucose intolerance following a 50g glucose load between 24 and 28 weeks, blood sample 1 hour later. Normal < 7.8. If very high risks (eg previous GDM) screen at 18 weeks as well
o If failed screening test then formal test is 75g fasting load with samples at 0,1 and 2 hours. Normal is <5.5, < 11 and < 8.5 at 0,1 and 2 hours. If any one is abnormal then GDM.
· Exam: includes checks of eyes (retinopathy) and hands and legs (neuropathy), urine for protein
· Aetiology: human placental lactogen (HPL, increases through pregnancy) ® insulin resistance ® insulin production. May unmask sub-clinical NIDDM.
o Diet and exercise (but don‟t calorie restrict them – ketosis is bad for babies)
o Regular monitoring – home glucose monitoring and Hb A1C – normal is less than 6.5, under 8 acceptable. Aiming for pretty tight control
o Insulin used if unable to control levels, or evidence of macrosomia. Stop once labour starts – requirements fall dramatically after delivery
o Sulphonylureas and metformin not approved in pregnancy
o ® ¯Frequency of macrosomia but less clear effect on perinatal mortality and rate of caesarean section
o Do GTT 6 weeks after delivery to check for type 1 or 2 diabetes
o Need to conceive when Hb A1C < 8. Even if tightly controlled, 4 – 5% risk of congenital abnormalities (2* general population). Most common are neural tube and heart defects
o Check for retinopathy at least twice during pregnancy
o Get baseline renal function and ECG/Echo if cardiac problems
o Usual insulin injections have shorter action Þ control harder. In early pregnancy, insulin requirements may reduce. Later they usually increase.
o Usually induced before term