Gestational diabetes mellitus (GDM) refers to varying degrees of abnormal glucose tolerance that occurs or is first detected during pregnancy and accounts for 80% to 90% of patients with gestational diabetes mellitus.
Pregnant women with GDM who have poor glycemic control can have many adverse effects on themselves and their offspring, and even form a vicious cycle. Data show that the glycemic control of pregnant women with GDM is closely related to neonatal outcomes, and good glycemic control can significantly reduce adverse neonatal outcomes such as giant fetuses and larger-than-gestational-age infants. Numerous studies at home and abroad have also shown that timely and aggressive treatment can reduce the incidence of giant babies, reduce birth injuries and cesarean deliveries, reduce the incidence of neonatal hypoglycemia, and bring the perinatal mortality rate of mothers and infants with GDM close to the population average. Therefore, the significance of early diagnosis of GDM is particularly important.
Diagnostic process and criteria of GDM
The old-fashioned diagnosis is based on the “two-step” method of the 50g GCT test.
50gGCT (glucose loading test): 50g of glucose (dissolved in 200mL of water and taken within 5min) is randomly given orally, and venous blood is drawn 1h after taking the glucose to check blood glucose.
The current diagnostic process and criteria have been simplified by using the 75g OGTT test “one-step method”: patients need to fast for eight hours before the test, and then take 75g of glucose within five minutes, and test the blood glucose for 1 hour and 2 hours respectively, and any of the blood glucose values meet or exceed the following criteria can be diagnosed as GDM.
75g of glucose OGTT
Fasting: 5.1mmol/L
1 hour after meal: 10.0mmol/L
2 hours after meal: 8.5 mmol/L
As can be seen from the above criteria, the diagnostic criteria for GDM are more stringent than those for patients with T1DM and T2DM, because a large number of studies have shown that the risk of adverse complications and birth outcomes for pregnant women and their offspring can be minimized to the greatest extent possible only if the blood glucose is lowered below the above criteria.
Timing of screening for GDM
There is a physiological basis for determining the appropriate timing of screening for GDM. At the beginning of pregnancy, in order to maintain glucose metabolic balance during pregnancy, pregnant women’s pancreatic β-cells proliferate and hypertrophy, and insulin secretion increases, compared with non-pregnant period, insulin secretion increases 2~5 times, and the increase of compensatory insulin secretion after meal is more obvious, and insulin secretion in the first time phase increases, so the period of early pregnancy is not suitable for screening GDM.
At 24-28 weeks of gestation, the placenta produces more insulin antagonist hormones, and the increase in weight and the decrease in insulin sensitivity of tissues after pregnancy leads to “physiological insulin resistance”. The peak secretion of insulin and C-peptide is delayed until 2 h after meal, and the insulin secretion in the first phase decreases, which is reflected in the increase and delay of postprandial glucose. Abnormal screening at this stage can make timely diagnosis of GDM and facilitate clinical management. If the screening in this phase is normal, but there are high-risk factors, it should be reviewed at 32~34 weeks. It is worth noting that for those who have polydipsia, polyphagia and polyuria as well as those who have positive urine glucose in early pregnancy, glucose screening should be performed at the first pregnancy test in order to diagnose early the diabetic patients who were missed before pregnancy.
People with high risk factors
Chinese, being of Southeast Asian descent, are also a high-risk group for GDM and should be promptly screened for GDM if they have the following conditions.
1, Age > 30 years, obese.
2, Pre-pregnancy with PCOS, irregular menstruation.
3, Family history of diabetes, especially first-degree relatives, maternal line.
4, Positive fasting urine glucose during early pregnancy.
5, history of abnormal obstetrics (history of GDM, RDS, malformations, history of fetal death intrauterine macrosomia).
6, suspected gigantism and excessive amniotic fluid in this pregnancy.
People who do not need to be screened
In 1997, the ADA proposed a selective screening protocol that suggested that pregnant women who meet the three criteria of “age <25 years, normal weight, and no family history of high risk" could be screened without ogtt, but its safety and economic implications have yet to be evaluated. < p="">
Proper diagnosis and treatment of GDM can help reduce the incidence of macrosomia, birth trauma, and cesarean delivery: reducing the incidence of stillbirths, malformations, and other diabetes-related comorbidities.
Since pregnant women with GDM have a 50% risk of developing diabetes, these potential DM patients should make early efforts to change poor lifestyle habits to prevent and delay the onset of diabetes.