Gestational diabetes

Diabetes mellitus may be a pre-existing problem or develop during pregnancy, gestational diabetes. It complicates up to 1 in 20 pregnancies. NICE estimates the following breakdown:

87.5% have gestational diabetes
7.5% have type 1 diabetes
5% have type 2 diabetes

Gestational diabetes

Gestational diabetes is the second most common medical disorder complicating pregnancy (after hypertension), affecting around 4% of pregnancies.

Risk factors for gestational diabetes

BMI of > 30 kg/m²
previous macrosomic baby weighing 4.5 kg or above
previous gestational diabetes
first-degree relative with diabetes
family origin with a high prevalence of diabetes (South Asian, black Caribbean and Middle Eastern)
unexplained stillbirth in a previous pregnancy

Screening for gestational diabetes

the oral glucose tolerance test (OGTT) is the test of choice
women who've previously had gestational diabetes: OGTT should be performed as soon as possible after booking and at 24-28 weeks if the first test is normal. NICE also recommend that early self-monitoring of blood glucose is an alternative to the OGTTs
women with any of the other risk factors should be offered an OGTT at 24-28 weeks

Diagnostic thresholds for gestational diabetes

these have recently been updated by NICE, gestational diabetes is diagnosed if either:
fasting glucose is >= 5.6 mmol/L
2-hour glucose is >= 7.8 mmol/L

Management of gestational diabetes

newly diagnosed women should be seen in a joint diabetes and antenatal clinic within a week
women should be taught about self-monitoring of blood glucose
advice about diet (including eating foods with a low glycaemic index) and exercise should be given
if the fasting plasma glucose level is < 7 mmol/l a trial of diet and exercise should be offered
- if glucose targets are not met within 1-2 weeks of altering diet/exercise metformin should be started
- if glucose targets are still not met insulin should be added to diet/exercise/metformin
- gestational diabetes is treated with short-acting, not long-acting, insulin
if at the time of diagnosis the fasting glucose level is >= 7 mmol/l insulin should be started
if the plasma glucose level is between 6-6.9 mmol/l, and there is evidence of complications such as macrosomia or hydramnios, insulin should be offered
glibenclamide should only be offered for women who cannot tolerate metformin or those who fail to meet the glucose targets with metformin but decline insulin treatment

Management of pre-existing diabetes

weight loss for women with BMI of > 27 kg/m^2
stop oral hypoglycaemic agents, apart from metformin, and commence insulin
folic acid 5 mg/day from pre-conception to 12 weeks gestation
detailed anomaly scan at 20 weeks including four-chamber view of the heart and outflow tracts
tight glycaemic control reduces complication rates
treat retinopathy as can worsen during pregnancy

Targets for self monitoring of pregnant women (pre-existing and gestational diabetes)

Time	Target
Fasting	5.3 mmol/l
1 hour after meals	7.8 mmol/l, or:
2 hour after meals	6.4 mmol/l

+PassMedicine Notes

Diabetes mellitus may be a pre-existing problem or develop during pregnancy, gestational diabetes. It complicates up to 1 in 20 pregnancies. NICE estimates the following breakdown:

87.5% have gestational diabetes
7.5% have type 1 diabetes
5% have type 2 diabetes

Gestational diabetes

Gestational diabetes is the second most common medical disorder complicating pregnancy (after hypertension), affecting around 4% of pregnancies.

Risk factors for gestational diabetes

BMI of > 30 kg/m²
previous macrosomic baby weighing 4.5 kg or above
previous gestational diabetes
first-degree relative with diabetes
family origin with a high prevalence of diabetes (South Asian, black Caribbean and Middle Eastern)
unexplained stillbirth in a previous pregnancy

Screening for gestational diabetes

the oral glucose tolerance test (OGTT) is the test of choice
women who've previously had gestational diabetes: OGTT should be performed as soon as possible after booking and at 24-28 weeks if the first test is normal. NICE also recommend that early self-monitoring of blood glucose is an alternative to the OGTTs
women with any of the other risk factors should be offered an OGTT at 24-28 weeks

Diagnostic thresholds for gestational diabetes

these have recently been updated by NICE, gestational diabetes is diagnosed if either:
fasting glucose is >= 5.6 mmol/L
2-hour glucose is >= 7.8 mmol/L

Management of gestational diabetes

newly diagnosed women should be seen in a joint diabetes and antenatal clinic within a week
women should be taught about self-monitoring of blood glucose
advice about diet (including eating foods with a low glycaemic index) and exercise should be given
if the fasting plasma glucose level is < 7 mmol/l a trial of diet and exercise should be offered

if glucose targets are not met within 1-2 weeks of altering diet/exercise metformin should be started
if glucose targets are still not met insulin should be added to diet/exercise/metformin
gestational diabetes is treated with short-acting, not long-acting, insulin

if at the time of diagnosis the fasting glucose level is >= 7 mmol/l insulin should be started
if the plasma glucose level is between 6-6.9 mmol/l, and there is evidence of complications such as macrosomia or hydramnios, insulin should be offered
glibenclamide should only be offered for women who cannot tolerate metformin or those who fail to meet the glucose targets with metformin but decline insulin treatment

Management of pre-existing diabetes

weight loss for women with BMI of > 27 kg/m^2
stop oral hypoglycaemic agents, apart from metformin, and commence insulin
folic acid 5 mg/day from pre-conception to 12 weeks gestation
detailed anomaly scan at 20 weeks including four-chamber view of the heart and outflow tracts
tight glycaemic control reduces complication rates
treat retinopathy as can worsen during pregnancy