Oral glucose resistance test

The oral glucose load test It is a very useful simple examination for the diagnosis of gestational diabetes. During pregnancy, a series of metabolic changes take place that are aimed at adapting the mother to the nutritional requirements of the fetus. One of the most important changes is the development of insulin resistance. Insulin is the hormone in charge of controlling glycemia, that is, the levels of glucose in the blood. A resistance to insulin will lead to an increase in its production to compensate for its low effectiveness, but on some occasions this increase may be insufficient and will lead to gestational diabetes. Gestational diabetes is any degree of glucose intolerance that is diagnosed during pregnancy.

There are different factors that predispose to the development of gestational diabetes. The presence of these factors allows pregnant women to be classified into three risk categories:

• High risk. They present one or more of the following factors: age equal to or greater than 35 years, obesity, macrosomia in previous deliveries, personal history of gestational diabetes, impaired glucose metabolism, or family history of diabetes.
• Moderate risk. Over 25 years of age without any of the listed risk factors.
• Low risk. Under 25 years without any risk factor.

Diagnostic screening with the O'Sullivan test is performed in all pregnant women between weeks 24-28 of pregnancy. The O'Sullivan test consists of determining blood glucose one hour after the administration of 50 grams of glucose orally. In high-risk patients, it should also be performed at the first pregnancy visit and between weeks 32-36 of gestation. In those with a moderate-low risk, the recommendation is to perform a single O'Sullivan test between weeks 24-28 of pregnancy.

In those cases in which the plasma glucose after one hour is equal to or greater than 140 mg / dl, the O'Sullivan test is considered positive and an oral glucose load should be performed to confirm the diagnosis of gestational diabetes. Oral glucose overload will also be performed in pregnant women who, without having performed the O'Sullivan test, have a fasting blood glucose between 85 and 125 mg / dl.

How is the study done?

The test is performed at rest. A vein in the forearm is usually channeled through a catheter. The catheter will facilitate extractions and avoid the need for repeated punctures during extractions. 100 grams of glucose are administered orally, measuring blood glucose levels at the beginning, one hour, 2 hours and 3 hours after administration. Normal values ​​are as follows: 105 mg / dl at baseline, 190 mg / dl at hour, 165 mg / dl at 2 hours, 145 mg / dl at 3 hours. It is considered diagnostic of gestational diabetes if two or more values ​​are equal to or greater than normal. If only one value exceeds the limits, it would be diagnosed with glucose intolerance in pregnancy and the test should be repeated in three or four weeks.

Preparation for the study

It should be done in the morning, after a fast of approximately 10-12h. It requires a diet with an amount equal to or greater than 150 gr / day of carbohydrates the three days prior to the study. During this period of time it is important that the patient has developed a normal physical activity.

What does it feel like during and after the study?

During the oral glucose load test, it is necessary to remain at rest, sit, and refrain from smoking. The discomfort during the study is the same that occurs in taking any blood sample. After extraction, there may be slight pain in the area of ​​the puncture, which tends to subside within minutes. Exceptionally, dizziness, nausea or fainting may occur, especially in patients with apprehension about blood draws.

Study risks

After venous blood extraction, a hematoma may occur, which will disappear within 5-10 days. In patients with anticoagulant or antiplatelet treatment, there may be persistent bleeding in the area of ​​the puncture, which will subside by applying pressure to the wound for a few minutes. It is a safe diagnostic test.

Study contraindications

The oral glucose load test has no contraindications.

Reasons why the study is carried out

Gestational diabetes is the most frequent complication in pregnant women, affecting around 10% of pregnancies. Its importance lies in the fact that gestational diabetes increases the risk of various obstetric complications such as: fetal distress, macrosomia, intrauterine death, polyhydramnios, cesarean deliveries and neonatal metabolic problems. It does not increase the incidence of congenital malformations.

Gestational diabetes has also been linked to long-term consequences for the child, such as the development of obesity, diabetes, inattention, or hyperactivity in childhood.