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Gestational Diabetes

Gestational diabetesGestational diabetes mellitus (GDM) is a type of diabetes that develops in pregnant women who were not diagnosed with diabetes before pregnancy. It can be defined as glucose intolerance, or impaired glucose tolerance (for more details, please read the “Prediabetes”) with onset or first recognition during pregnancy. This definition is applicable to both situations when patients had previously undiagnosed diabetes and when patients developed diabetes concurrently with pregnancy.

Insulin resistance usually emerges in the second trimester of pregnancy and is at its highest level in the third trimester. At this period, it may be of the same level as in non-pregnant patients with type 2 diabetes mellitus.

The mechanism of glucose intolerance leading to gestational diabetes is still not fully clear. It is thought that body of a pregnant woman secures glucose to supply the fetus. Due to developing insulin resistance, more glucose remains in blood instead of being absorbed by the cells. As a reaction to this, the body automatically starts producing more insulin. Excessive amounts of insulin stimulate the growth of fetus, which often results in macrosomia – large body as for gestational age. What is more, excessive glucose that travels though placenta increases the glucose levels in fetus, which later causes high insulin production and susceptibility to hypoglycaemia in newborns.

In most cases, gestation diabetes resolves after the delivery. Nevertheless, there remains a risk of developing diabetes in future. This especially concerns women requiring insulin treatment, women having diabetes-associated antibodies, history of more than two previous pregnancies, and obesity. Women who experienced GDM during pregnancy face the 30-84% risk of recurrence during second pregnancy within 1 year. Besides, children born by women with gestational diabetes run an increases risk of obesity and type 2 diabetes development later in life.

Types of Gestational Diabetes

According to the White classification of GDM, there are two types of diabetes that affect perinatal outcome: Type A – gestational diabetes, i.e. diabetes that developed during pregnancy, and pregestational diabetes that developed prior to pregnancy. Gestational diabetes has two subtypes:

  • Type A1 gestational diabetes is characterized by abnormal result of oral glucose tolerance test and normal levels of blood glucose during fasting and 2 hours after meal at the same time. This type of gestational diabetes is not severe and can be managed by diet.
  • Type A2 gestational diabetes is characterized by both abnormal result of oral glucose tolerance test and abnormal levels of blood glucose during fasting and 2 hours after meal. To manage this type of gestational diabetes, insulin or anti-diabetic drug therapy is required.

Risk Factors

There are a number of factors that increase the risk of developing gestational diabetes. These are the following:

  • Age over 35 years
  • High-risk ethnic group (Asians, African-Americans, Afro-Caribbeans, Hispanics, Pacific Islanders, native Americans)
  • Previous diagnosis of gestational diabetes or prediabetes including impaired glucose tolerance (glucose intolerance) or impaired fasting glycaemia
  • Family history of type 2 diabetes in a first-degree relative
  • Excessive weight or obesity
  • Previous pregnancy that resulted in a child with high weight as for gestational age
  • Previous poor obstetric history
  • Polycystic ovarian syndrome
  • Smoking

It is highly recommended for all women to pass screening during pregnancy, as about 40-60% of women with gestational diabetes do not belong to any of the above listed risk-groups. Even more, the biggest part of women with GDM experience no classical symptoms of diabetes mellitus.

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