Generality
GCT is the acronym for Glucose Challenge Test, a test indicated for the screening of gestational diabetes, also known as the "glycemic curve in pregnancy".
The test run is similar to that seen for the OGTT, better known as the oral glucose load test, but with some differences.In GCT, first of all, preventive fasting is not necessary and the oral glucose solution is no more than 75 but 100 grams.
What's this
The glycemic curve in pregnancy is useful for the diagnosis of gestational diabetes. This clinical test therefore allows to identify the presence of alterations in carbohydrate metabolism during gestation.
Also defined by the acronym GCT (from the English “Glucose Challenge Test”), the glycemic curve in pregnancy consists of the measurement of the blood sugar concentration, before and after the oral administration of a certain quantity of standard glucose solution.
Because it is measured
The test is used to screen for diabetes that has arisen in pregnancy (gestational diabetes) and is prescribed to all mothers-to-be between the 24th and 28th week of gestation, if they have at least one of the following risk factors:
- Family history of diabetes in first degree relatives;
- Fetal macrosomia (weight of the unborn child> 4.5 kg) in previous pregnancies;
- Overweight / Obesity (BMI ≥25 kg / m2);
- Age greater than or equal to 35 years;
- High-risk ethnic groups (South Asia, Middle East, Caribbean).
The glycemic curve is anticipated between the 16th and 18th week of pregnancy in case of overweight, poor control of the lipid profile, previous gestational diabetes and fasting glycaemia equal to 100-125 mg / dl, at the beginning of gestation or in the past. In women who have been diagnosed with gestational diabetes, then, the examination is performed as a control, 8-12 weeks after delivery.
Pregnant women with pre-gestational diabetes (ie pre-existing pregnancy) are instead subjected to intensive metabolic monitoring to carefully monitor the level of glucose in the blood.
Elevated glycemic values during pregnancy can be associated, in fact, with a series of maternal-fetal complications, such as:
- Recurrent urinary and vulvovaginal infections;
- Fetal malformations;
- Hypertension (gestosis);
- Miscarriage;
- Late fetal death (3rd trimester);
- Preterm birth
- Presence of excessive amniotic fluid;
- Excessive development of the fetus (macrosomia).
Normal values
The values of the glycemic curve during pregnancy are considered normal:
- Immediately after taking the glucose solution: up to 95 mg / dl;
- After 60 minutes: up to 180 mg / dl;
- After 120 minutes: less than 155 mg / dl.
Altered Glycemic Curve - Causes
During pregnancy, the alteration of the glycemic curve may indicate the presence of gestational diabetes.
During pregnancy, the release of hormones of placental origin occurs which determine an "increased resistance of the tissues to the action of" insulin (insulin resistance). Within certain limits, this "event can be considered" physiological ", as it is aimed the best use of the nutrients necessary for fetal growth. However, if this "resistance" prevents the insulin from functioning optimally, if it is boosted by other risk factors and if it is not sufficiently compensated by the extra secretion from the pancreas, the blood sugar tends to remain at high levels until it evolves in the gestational diabetes.
How it is measured
The glycemic curve in pregnancy can be performed by administering different dosages of glucose:
- 50 g (GCT): is the screening test for gestational diabetes;
- 100 g (OGTT): it is the confirmation test for gestational diabetes, to be performed when the GCT shows a blood glucose value> 140 mg / dl at 60 minutes.
