Generality
Gestational diabetes (GDM) is a metabolic disorder characterized by reduced glucose tolerance (and less frequently by franc diabetes), which occurs or is diagnosed for the first time during pregnancy .
Causes
Hormonal disruptions related to pregnancy increase insulin resistance, making the cells less sensitive to its action. The pancreas, for its part, is not always able to compensate for this deficit through a proportional increase in the synthesis and release of insulin.
Gestational diabetes is therefore a "physiological" phenomenon in some respects, which as such does not normally involve serious dangers for the mother and the unborn child. It is well known, in fact, that the period most at risk of congenital fetal malformations is that between conception and the tenth week of pregnancy, while gestational diabetes tends to occur typically after the twenty-fourth week, when the development of organs and systems is now completed.
To prevent complications, which in particular circumstances may also become important, it is essential to maintain the glycemic balance within the recommended limits, with a renewed gesture of love for oneself and the child.
Symptoms and Risk Factors
To learn more: Gestational Diabetes Symptoms
The symptomatology of gestational diabetes is absent most of the time. Rarely, the expectant mother may notice signs and symptoms typical of hyperglycemia, such as increased thirst (polydipsia) and urination (polyuria), nausea and vomiting, urinary tract infections and blurred vision.
Low risk of gestational diabetes
- age <25 years
- normal weight before pregnancy
- normal birth weight
- ethnicity with a low prevalence of gestational diabetes
- absence of diabetes in first-degree relatives
- absence of previous hyperglycemia
- absence of previous obstetric problems
NOTE: screening glycemic tests are not required ONLY if all the above criteria are met.
High risk of gestational diabetes
- positive family history of diabetes in first-degree relatives
- previous history of GDM, reduced glucose tolerance, impaired fasting glucose or glycosuria
- macrosomia in previous pregnancies
- obesity
- marked glycosuria in ongoing pregnancy
NOTE: perform glycemic tests as soon as possible if one or more of the above conditions are present.
Medium risk of gestational diabetes
- patients who do not meet the high risk criteria, nor those of low risk
Additional risk factors
- Smoking and polycystic ovary syndrome
Screening
Precisely because of its tendency to run asymptomatically or paucisintomatically, the identification of gestational diabetes cannot be separated from an accurate screening, even more important if it is seen as a precious opportunity to reduce the frequency of maternal and fetal morbidity, and various complications .
The term screening refers to a clinical procedure that has no diagnostic purpose, but simply to identify a subgroup at risk for a given pathology. For the definitive diagnosis, individuals who are "positive" in a screening test must therefore undergo a further assessment, which - if it is positive - will allow early treatment capable of producing the best possible benefit.
Depending on the bibliography and the guidelines consulted, this screening:
- it must be universal, that is conducted on all pregnancies between the 24th-28th week of gestation, possibly anticipating it to the 14th-18th in the presence of serious risk factors (strategy followed by many centers);
or:
- it is not necessary in low-risk women;
- should be performed between the 24th and 28th week of pregnancy in women at medium risk;
- it must be performed as early as possible, that is between the 14th and 16th week, in high-risk women, who also - in the case of negativity - must undergo the test again at 24-28 weeks. The risk identification criteria are shown in the table to the side and for obvious reasons they should be identified before the start of pregnancy.
Diagnosis
Currently there is no unequivocal consensus at international level on the methods of screening and diagnosis of gestational diabetes; for the same reason there is no uniformity in epidemiological data. The incidence of gestational diabetes - which has increased significantly in recent decades, probably due to a sedentary lifestyle, changed eating habits and the increase in the average age of pregnant women - can be estimated at 10-20% of the population over the age of 35 years and, as far as the Italian one is concerned, at around 6% (average figure that takes into account all age groups).
The most widespread screening method is called GCT, an acronym for Glucose Challenge Test . Basically, it is a glucose loading test with 50 g of glucose and determination of the glycaemia 60 minutes after ingestion of the glucose solution.
If after one hour the blood sugar is greater than or equal to 140 mg / dl, but less than 180 mg / dl (7.8-10.2 mmol / L), the test is positive, even if it is not yet possible to speak of gestational diabetes. To obtain diagnostic confirmation, the oral load must be carried out with 100 grams of glucose (OGTT), this time fasting for 8-12 hours. It is not necessary to resort to this test if the glycaemia exceeds 198 mg / dl, an element already sufficient to diagnose diabetes. During OGTT at 100 grams, glycaemia is measured at regular time intervals, fasting and after 60, 120 and 180 minutes after ingestion of the first sip of glucose solution: if two or more glycemic values are higher than the reference ones, there is a diagnosis of gestational diabetes; if only one value is higher, a diagnosis of carbohydrate intolerance is made in pregnancy.
OGTT at 100 g for the research of gestational diabetes, interpretation of results, limits of normality | Fasting: | Less than 95 mg / dL or 5.2 mmol / L |
| 60 minutes: | Less than 180 mg / dL or 10.0 mmol / L | |
| 120 minutes: | Less than 155 mg / dL or 8.6 mmol / L | |
| 180 minutes: | Less than 140 mg / dL or 7.7 mmol / L |
Further information on the execution of the GCT and OGTT tests
If the suspicion of manifest hyperglycaemia is high (eg presence of polyuria and polydipsia) the measurement of basal blood glucose may be sufficient to confirm the diagnosis of diabetes; in this case a baseline glucose value> 126 mg / dl or an occasional value> 200 mg / dl are to be considered diagnostic for diabetes mellitus, provided they are confirmed by a second check.
Longitudinal studies are underway to assess whether the single-step implementation of the standard glucose loading test (approved for non-pregnant subjects) with 75 g of glucose and glycemic control at 2 hours of loading, may be applied instead of loading glucose of 100 g described above. The next data should therefore dampen the "endless" controversy over the diagnosis of gestational diabetes, proposing a homogeneous reference model.
