Gestational Diabetes - Symptoms, Diagnosis and Treatment

Like any type of diabetes, gestational diabetes is a disease that affects the way the cells use glucose (sugar), causing high levels of this substance in the blood, a situation that can affect the course of pregnancy and the health of the baby.

Gestational diabetes
Gestational diabetes

What is gestational diabetes?

Gestational diabetes is a type of diabetes that presents a particularity, it arises during pregnancy and usually disappears after the birth of the baby. Women who are diabetic and become pregnant are not considered to have gestational diabetes. Gestational diabetes is one that appears only after the onset of pregnancy.

Gestational diabetes is a common complication of pregnancy, affecting, depending on the region, between 2% and 15% of pregnant women.

Compared to non-pregnant women, pregnant women tend to be at increased risk of hypoglycemia (low blood glucose) during off-meal periods and during sleep. This is because the fetus continuously extracts glucose from the mother, even when it is fasting. As the fetus grows, the greater your need for glucose.

From the second trimester of pregnancy, as the baby starts to get big, the mother needs protective mechanisms against hypoglycemia, as the fetal glucose intake becomes intense. This protection comes from hormones naturally produced by the placenta, such as estrogens, progesterone and chorionic somatomammotropin, which act by decreasing the insulin's action power, making more glucose available in the bloodstream.

The anti-insulin effect of these hormones is so strong that at the end of pregnancy, the mother's pancreas needs to produce up to 50% more insulin to prevent hyperglycemia (elevated blood glucose levels). Gestational diabetes arises exactly in pregnant women who can not increase the action of their insulin to compensate for the hyperglycemic effects of pregnancy hormones.

Mothers with gestational diabetes have elevated blood glucose levels, especially after meals, which is the time when the body gets a large glucose load coming from food.

Gestational diabetes usually only arises from the middle of the second trimester, usually only after the 20th week of gestation.

Risk factors

We do not know exactly why in some pregnant women the mechanisms of glycemic control (blood glucose) become uncontrollable, leading to gestational diabetes. We know, however, that some personal characteristics increase the risk of a pregnant woman developing gestational diabetes. Are they:
  • Family history of diabetes mellitus.
  • Have already had blood tests with altered glucose at some point before pregnancy.
  • Excess weight before and/or during pregnancy.
  • Age greater than 25 years.
  • Previous pregnancy with a fetus born more than 4 kg.
  • History of spontaneous abortion with no informed cause.
  • Have had a previous child with malformation.
  • Have high blood pressure.
  • Have or have had previous pre-eclampsia or eclampsia.
  • Have polycystic ovary syndrome.
  • Make use of corticosteroids.

Symptoms of diabetes in pregnancy

Unlike other forms of diabetes, which occur with symptoms such as weight loss, excessive thirst, excess urine, blurred vision and constant hunger, gestational diabetes does not usually cause symptoms. It is always good to remember that symptoms such as increased urinary frequency, tiredness and changes in the pattern of hunger are common in pregnancy, not serving as a parameter for the identification of gestational diabetes.

Therefore, without performing screening laboratory tests, it is not possible to identify pregnant women with gestational diabetes.

Diagnosis of gestational diabetes

Screening for gestational diabetes is usually done between the 24th and 28th weeks of gestation. In pregnant women with high risk, the investigation can be done earlier. Many obstetricians start the research for all pregnant women already at the first appointment, by dosing fasting blood glucose.

Currently, there is more than one way to screen for gestational diabetes. There is no broad consensus on the best method. The Brazilian, American and European schools propose slightly different methods, based on studies of the characteristics of their own populations. Therefore, depending on the source being investigated, the method of diagnosing gestational diabetes may be different. We will present here the guidelines of the Brazilian Association of Gynecology and Obstetrics Associations (FEBRASGO), which are the same as those of the International Association of Diabetes in Pregnancy Study Group (IADPSG).

All pregnant women should measure their fasting glucose at the first prenatal visit. The expected value is less than 85 mg/dl. If the patient has a fasting blood glucose lower than 85 mg/dl and has no risk factor for gestational diabetes, no further research is needed unless gestational diabetes develops during the course of pregnancy.

If the patient has a result above 126 mg/dl on fasting glucose at the first visit, this is indicative of diabetes mellitus. The examination should be repeated 1 or 2 weeks later for confirmation.

Pregnant women with fasting glycemia between 85 and 125 mg/dl are not considered diabetic, but are in the high-risk group, especially those with glycemia closer to 125 mg/dl. In this group, a new study, called a glycemic curve or oral glucose tolerance test, should be done between the 24th and the 28th week of pregnancy.

In the oral glucose tolerance test, the pregnant woman collects blood for glycemia in 3 moments. The first is fasting. Then the pregnant woman consumes a syrup containing 75 grams of glucose, waits for 1 hour and reuses the blood. 2 hours after the syrup is ingested, the pregnant woman collects the blood for the 3rd and last time.

The diagnosis of gestational diabetes is made in that the patient has at least 2 of the 3 altered results:
  • Glycemia Fasting: normal up to 92 mg/dl
  • Glycemia after 1 hour: normal up to 180 mg/dl
  • Glycemia after 2 hours: normal up to 153 mg/dl

As already mentioned, this protocol described is only one of several. This is the best way to research gestational diabetes in the Brazilian population, but it is not the only correct one.

Consequences of diabetes in pregnancy

Gestational diabetes carries risks to gestation and the baby. Excess glucose circulating in the mother's blood crosses the placenta and reaches the fetus, filling it with glucose. The fetal pancreas begins to produce large amounts of insulin in an attempt to control fetal hyperglycemia. Insulin is a hormone that stimulates growth and weight gain, causing the fetus to grow excessively. Fetuses of mothers with gestational diabetes usually are born with more than 4 kg and need to undergo cesarean delivery.

Infants born to mothers with untreated gestational diabetes have a higher risk of intrauterine death, cardiac and respiratory problems, jaundice and episodes of postpartum hypoglycaemia. As adults, the risk of obesity and type 2 diabetes mellitus is also higher than in the general population.

On the mother's side, gestational diabetes increases the risk of miscarriage, preterm birth, and pre-eclampsia.

Treatment of gestational diabetes

Controlling blood glucose levels is essential for maternal and fetal health. For overweight or obese women it is imperative to lose weight. A healthy diet with fat, carbohydrate and calorie control is indicated for all pregnant women. Physical exercises are also important as they help in the functioning of insulin.

If changing lifestyle habits do not result in glucose control, the pregnant woman may need to use insulin injections.

In poorly controlled cases, if the patient does not naturally enter labor, labor is induced at week 39 to prevent the fetus from growing too much in the uterus.

Does gestational diabetes have a cure?

In most cases, diabetes disappears spontaneously after the baby is born, but these mothers are at high risk for developing type 2 diabetes throughout their lives if they do not control their weight, diet and do not engage in regular physical activity.

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