Diabetes in Pregnancy: Causes, Symptoms, Managing Gestational DM

What changes occur during pregnancy due to Diabetes?

During first trimester insulin action is increased because of the rise in estrogen and progesterone.
Morning sickness and decreased food intake tend to lower blood glucose.
Later in pregnancy, growth of placenta and elaboration of placental lactogen (hpl) lead to development of insulin resistance. High levels of prolactin and cortisol add to problem and further raise insulin resistance.
Physiologically, fasting plasma glucose tends to be low as during over night fasting, glucose and amino-acids go to the foetus. The mother has to depend on free fatty acids and ketones for energy requirements. Thus she remains in state of accelerated starvation and on the other hand, hyperglycemia tends to occur following usual meals.

These phenomenons are exaggerated in third trimester.

Major problems in foetus arise from hyperglycemia and hyper-ketonaemia as these are known to be teratogenic in 8-10 weeks of gestation. Therefore, congenital malformation is 3-5 times more common in diabetic pregnancies.
Most abortions occur due to foetal deformity. Glucose and amino-acids pass freely through placenta while insulin does not. Foetal pancreas starts secreting insulin by 12th week. Maternal hyperglycemia raises foetal blood sugar levels, evoking rise in insulin secretion. This leads to increased lipogenesis and rate of foetal growth from 30th week. Therefore infants of diabetic mother are longer and heavier than normal infants (macrosomia).
Premature labor is common due to placental abnormalities. Hyper-insulinaemia in later pregnancy leads to deposition of more glycogen in pulmonary alveolar tissue causing delay in lung maturity as a result respiratory distress syndrome is common.
In addition there is high incidence of intrauterine deaths leading to still births.

Pre-gestational diabetes: Pregnancy occurring in a known diabetic person. Here background retinopathy is aggravated during pregnancy and usually regresses after delivery. Early clinical nephropathy may progress to massive proteinuria in 3rd trimester. Diabetic mothers with vascular complications are likely to have babies, small for gestational age or also called as premature labor.
Gestational diabetes (GDM): Defined as carbohydrate intolerance of variable severity with onset or first recognition during pregnancy. Macrosomia, stillbirths and polyhydramnois occur more in gestational diabetes. Detection of GDM is commonly made after 20th weeks. GDM in White’s classification is divided into:

Gestational diabetes diet - when fasting BSL or blood sugar levels is below 105 mg/dl and random is 120 mg/dl, patient may be managed on diet.
Gestational diabetes insulin - when fasting BSL is 120 mg/dl and post-prandial exceeds 150 mg/dl, insulin has to be given.

Dietary allowance of 30-35 kcal/kg of desired weight is recommended in both types.
Close monitoring of BSL needed to maintain fasting BSL to 65-90 mg/dl and post-prandial BSL to 100-135 mg/dl and insulin doses are to be adjusted accordingly.
Foetal monitoring to be done closely. Ultra-sonography at 10th week to assess gestational age, at 15-16th weeks for cardio-vascular malformation and Alfa-feto protein test at 16-17th weeks to assess NTG.

Delivery is usually planned nowadays with lower section Cesarean section (LSCS).