This is a test conducted after the patient has fasted overnight, typically starting at 10 p.m. the night before. A blood sample will be taken in the morning. The patient is then required to drink a sugary drink (75 gm of glucose diluted in 250 ml of water), and another blood sample will be taken 2 hours later.
Plan on eating three healthy meals and snacks for 3 days before the test. You do not need to buy special food, but you do need to make sure you have healthy foods to eat. Your meals should be balanced with plenty of carbohydrates such as breads, cereal and pasta.
Do not eat, smoke, or do heavy exercise 12 hours before the test. (For example: If your test is scheduled for first thing in the morning, at 8 AM—Do not eat, smoke, or do heavy exercise after 8pm the night before). You may drink plain, not flavored, water.
When is the glucose tolerance test done?
Women at risk to develop GDM such as the fasting plasma glucose ≥7.0 mmol/L or the random plasma glucose (RPG) ≥11.1 mmol/, they should do the glucose tolerance test during booking or as early as possible. However, women age of more than 25 with no other risk factors, glucose tolerance test is usually done at 24-28 weeks of gestation
If any one of the two items reaches or exceeds the limit, that is, fasting plasma glucose more or equal to 5.1 mmol/ and two hours after taking the sugar more or equal to mmol/L is considered as the woman is having gestational diabetes mellitus. The doctor will repeat the glucose tolerance test at 24 to 28 weeks if the first test is negative.
Is glucose tolerance testing useful during pregnancy?
If your blood glucose levels are high, it will be transferred to the fetus via the placenta, exposing the fetus to high levels of blood glucose, resulting in macrosomia (defined as a baby born with body weight ? 4.0 kg).
The baby is also at risk of prolonged jaundice, electrolyte imbalances, breathing difficulties and congenital abnormalities. Macrocosmic babies tend to develop into obese adults in the future, risk of developing Type 2 Diabetes is high.
Ultrasound examination antenatally is useful to monitor the size of the growing fetus and to detect the presence of polyhydramnios. Like other diabetes patients, women with GDM are at high risk of experiencing complications such as urinary tract infections, diabetic ketoacidosis, and fungal skin infection. They are also susceptible for preterm deliveries due to polyhydramnios and big babies.
GDM also causes complications during delivery, resulting in a difficult delivery and higher rates of Caesarean sections. You are also at higher risk of getting pre-eclampsia and future subsequent pregnancies.