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During pregnancy there is a high risk of high blood sugar. To prevent this, a special glucose tolerance test is performed. It allows you to determine how “tolerant” the body of the expectant mother to glucose and whether there is a negative effect on the body. If the tolerance level is higher than normal in the blood, a special treatment is prescribed.
In the sixth month of pregnancy, glucose tolerance is determined with a special test. This allows detection of hidden diabetes. It can be detected in 3-6% of pregnant women. It is commonly believed that gestational diabetes occurs only in pregnant women, as it is triggered by pregnancy hormones. In other words, after delivery, it will disappear immediately and the future mother will not have to suffer from it for the rest of her life.
Checking glucose tolerance in pregnancy is very important, as it helps prevent a number of undesirable consequences, including the birth of a large fetus or prenatal complications. The second name of the glucose tolerance test is the O’Sullivan Test, after the scientist who invented it. As such, there is no alternative to GTT with similar efficacy, but different techniques are occasionally used.
What is the glucose tolerance test
Pregnancy diabetes mellitus is a condition where the body has impaired glucose tolerance. It occurs or is determined during pregnancy. This disorder is not within the scope of normal diabetes mellitus, but is still a serious medical problem. In the absence of glucose tolerance, certain health risks are established for the mother and fetus. In addition, there is a high probability that the woman will develop type 2 diabetes in the future.
During pregnancy, insulin resistance increases significantly. In addition, insulin secretion increases compensatorily and may even lead to hyperinsulinemia. During the first trimester and the first half of the second trimester, blood glucose levels are lower than in non-pregnant women. Only by the second trimester does insulin resistance occur. Throughout pregnancy it gradually increases.
This phenomenon has a certain physiological meaning. It consists in the adequate supply of glucose to the fetus. This mechanism depends very much on the influence of hormones secreted by the placenta. If gestational diabetes occurs, changes in insulin resistance become more pronounced compared to those in a normal pregnancy.
The test allows us to determine the blood sugar level and how susceptible the mother and fetus are to glucose, the effects of its effects.
When is it necessary to perform a GTT
There are several factors that determine when it is necessary to conduct a glucose tolerance test:
- If questionable glycemic values are found (allows you to clarify the status of carbohydrate metabolism);
- If there are risks of diabetes mellitus development;
- BMI over 25 kg/m2;
- diabetes mellitus is in the family anamnesis;
- low physical activity on a regular basis;
- blood pressure problems;
- impaired lipid metabolism;
In turn, it is also worth highlighting several factors when the test is prohibited:
- any acute, including infectious disease is present;
- In the case of the need to take medications that lead to an increase in glycemia (preferably cancel them three days before the GTT);
- gestational age over 32 weeks;
Keep in mind that this test is not always required. As a rule, its prescription occurs on an individual basis, after the attending physician’s evaluation of the general well-being of the woman in labor and tests.
How to prepare for the test
The glucose tolerance test is carried out with the preservation of the usual diet. There is only one condition: you cannot reduce carbohydrate intake below 150 grams per day for at least 3 days before the test. GTT is performed in the morning on an empty stomach, and the last meal should be 8-14 hours before the test. The night before dinner should contain 30-50 grams of carbohydrates.
Water is allowed to be drunk during the test, and the pregnant woman should take a sitting position. Until the end of the test is strictly prohibited smoking. In addition, prior to the procedure to test glucose tolerance is prohibited taking any medications that may affect the results.
Stages of the test
Determining glucose tolerance is conducted in two phases:
- Phase 1. At up to 24 weeks (usually immediately after confirmation of pregnancy), one of the following tests is mandatory: fasting venous plasma/serum glucose intake, glycosylated hemoglobin test, venous plasma/serum glucose at any time of day without reference to food.
- Phase #2. GTT is performed at 24-28 weeks of pregnancy. This phase is mandatory for all pregnant women with risk factors. This category includes patients with undetected abnormalities in phase 1.
The glucose tolerance test in pregnancy has certain specifics that must also be considered.
The norm and evaluation of the test results
Only a doctor – obstetrician, therapist, endocrinologist – can interpret the results of the GTT. The norm of glucose tolerance in pregnancy is determined by the following indicators: on an empty stomach – less than 5.1 mmol/l, one hour later – less than 10 mmol/l, two hours later – 8.5 mmol/l. If after testing at least one of these values is exceeded, it already indicates a corresponding diagnosis of GAD.
Attention should also be paid to the presence of reference values. Thus, the reference values of plasma glucose, when measured on an empty stomach during pregnancy is from 4.1 to 5.1 mmol/l. The main criterion for the norm:
There are several reasons why glucose tolerance may be elevated:
- Impaired carbohydrate metabolism;
- a false positive result due to an acute illness, surgery or any other stressful situation;
- taking medications that affect the increase in glycemia.
Separately, it is worth considering the reasons why glucose tolerance in pregnancy is elevated: taking medications that affect glycemic reduction (insulin, various blood glucose-lowering drugs), insulinoma, excessive fasting or intense physical activity on the eve of the test.
Alternatives to GGT
GGT is not performed if there are any diseases in the acute stage. Even a common runny nose fits under this category. Any changes of this kind have a strong impact on the results of the study. In addition, it is worth highlighting several reasons that may show a false result in determining glucose tolerance.
For example, it is possible if an eight-hour diet was not observed before the blood test. In addition, if significant dietary changes occurred three days before the test, such as increased or decreased carbohydrate intake, this may also affect the GGT results. Carbohydrate metabolism disorders, excessive physical activity, strong stress situations, infectious diseases – all this directly affects the final results.
Depending on how glucose load is injected into the body, there are two types of GGT – oral and intravenous. The second method is used if during pregnancy the expectant mother for some reason cannot consume the “sweet cocktail” intravenously. The test itself is not dangerous.
In the case that the study is performed with a load, there is a risk of an overdose of blood sugar levels. This is due to the fact that pregnant women already have high glucose levels – symptoms that clearly indicate a disturbed carbohydrate metabolism will start to occur.
The glucose tolerance test is done for a reason. The test is performed only if there is serious suspicion of diabetes. There are no analogues of this study, but given that blood is given once per trimester on a mandatory basis, it is possible to know the blood sugar level and without additional burden.
Recommendations for pregnant women
In the case of reduced glucose tolerance, it is required to follow a special diet. It is determined taking into account the body mass index of the pregnant woman and her taste preferences. This makes it possible to maintain normal sugar levels. If a special diet is prescribed, a complete elimination of simple carbohydrates is recommended, as well as a limited consumption of complex carbohydrates.
Additionally, a sufficient amount of protein is required – meat, fish, seafood, dairy and fermented dairy products. The diet during pregnancy should be enriched with fiber and vitamins – greens, vegetables, sour-sweet berries. Particular attention should be paid to the correct choice of fats in accordance with the amount prescribed by the doctor. Animal fats are completely under restriction.
Instead of frying and using a deep fryer, dishes should be boiled, stewed, baked and steamed. At the detection of gestational diabetes mellitus doctor will draw up a special menu, which should be observed until the end of pregnancy. At the same time, it is mandatory to take into account the individual characteristics of each woman.
Pregnant women should not use Table 9 in its pure form, because of the substantial limitation of its caloric content. The doctor will tell you about the diet plan in detail at a face-to-face consultation. If it is not possible to achieve the desired level of glucose tolerance with a diet, as well as in the case of a negative impact on the fetus, medications are prescribed, namely insulin.
Pregnant women should not use blood glucose-lowering drugs in the form of tablets. Insulin therapy is prescribed by an endocrinologist. During the whole period of pregnancy, women must be under the constant supervision of three doctors: an endocrinologist, a general practitioner and an obstetrician-gynecologist. Patients should be sure to adhere to regular physical activity. This can be walks in the fresh air, special yoga or swimming.