Obstetrics

Question 1

What is gestational diabetes?

Answer 1

any degree of glucose intolerance with onset or first recognition during pregnancy

1 in 5 pregnancies are affected

Question 2

What are the RF for gestational diabetes?

Answer 2

previous GD
FH of diabetes with 1st degree
Prev macrocosmic baby >4.5kg
Obesity
High prevalence in place of family origin
PCOS
Maternal age >40

Question 3

What is the pathophysiology of gestational diabetes?

Answer 3

In pregnancy, there is progressive insulin resistance. This means that a higher volume of insulin is needed in response to a normal level of blood glucose. On average, insulin requirements rise by 30% during pregnancy.

A woman with a borderline pancreatic reserve is unable to respond to the increased insulin requirements, resulting in transient hyperglycaemia. After the pregnancy, insulin resistance falls – and the hyperglycaemia usually resolves.

Question 4

How does Gestational Diabetes present?

Answer 4

Can be asymptomatic and just picked up on screening Increased fluid (polyhydramnios)
Large for gestational age fetus > 90th centile
Glycosuria of +2 or +1 or more than more occasion

Question 5

How is gestational diabetes screened for?

Answer 5

Booking – if previous gestational diabetes then at 13-14 weeks

24 – 28 weeks’ gestation – if risk factors are present or in cases of previous gestational diabetes.

Any point during pregnancy – if 2+ glycosuria on one occasion, or 1+ on two occasions. Alternatively, pre- and postprandial blood sugar monitoring can be performed.

Question 6

How is the OGTT done?

Answer 6

Fasting blood glucose and blood glucose 2 hours after 75g of glucose

Fasting > 5.6
2 hours > 7.8

Question 7

What are fetal complications of gestational diabetes?

Answer 7

• Macrosomia – can cause shoulder dystocia, obstructed/delayed labour, and/or higher rates of instrumental deliveries.
• Organomegaly (particularly cardiomegaly)
• Erythropoiesis (resulting in polycythaemia)
• Polyhydramnios
• Increased rates of pre-term delivery
• Hypoglycaemia after delivery
• Reduction in pulmonary phospholipids, which decreases fetal surfactant production which can cause transient tachypnoea of the newborn

Question 8

Why does high maternal blood sugar cause macrosomia?

Answer 8

In pregnancy, glucose is transported across the placenta, but insulin is not. This can cause fetal hyperglycaemia if there is a high level of glucose in the maternal circulation. Subsequently, the fetus will increase its own insulin levels to compensate; hyperinsulinaemia. Insulin is a hormone that has a similar structure to growth promotors.

Question 9

How is gestational diabetes managed?

Answer 9

Lifestyle advice + regular glucose checks (4/day)
Consultant led care
Growth scans at 28, 32 and 36 weeks, to monitor for large growth or polyhydramnios
Deliver early:
- deliver at 37 to 38 weeks if they are on treatment
- induction of labour or caesarean section before 40+6 if managed by diet
- Meds - metformin, insulin or glibenclamide (sulfonylurea)

Question 10

What medications are used in gestational diabetes?

Answer 10

Medication:
- Metformin
- Glibenclamide – used if metformin is not tolerated (often due to GI side effects) and insulin has been declined.
- Insulin - Consider starting at diagnosis if the fasting glucose >7.0mmol/L.
Or introduce later in pregnancy if
(i) pre meal glucose > 6.0mmol/L
(ii) post meal glucose >7.5mmol/L
(iii) fetal AC (abdominal circumference) >95th centile

Question 11

What is done about gestational diabetes post-natally?

Answer 11

• All anti-diabetic medication should be stopped immediately after delivery.
• Check blood glucose before discharge
• Fasting glucose test 6-13 weeks post-partum
• Yearly glucose tests because of increased risk of developing diabetes in the future
• In subsequent pregnancies, an OGTT should be offered at booking and at 24 – 28 weeks’ gestation.
• Women with existing diabetes should decrease their insulin after birth and when breastfeeding