*1.4.3.2 Diagnostic standard for GDM*

The Oral Glucose Tolerance Test (OGTT) is the gold standard for diagnosing GDM. The procedure involves eating a balanced diet containing at least 150 g of carbohydrates per day for 3 days prior to the test, which is followed by a period of fasting (no ingestion of any food) for 8 to 14 hours before the test.

The first blood sample is taken by 9 a.m. for measurement of the fasting blood glucose. After that, the patient is given a drink of 75-g glucose load (75-g glucose dissolved in 300 ml of water, consumed within 5 minutes). Following the ingestion of the glucose solution, blood samples are taken at 1 and 2-hour intervals to measure the blood glucose levels post-ingestion. During the waiting period, smoking, eating, or drinking any other fluids is prohibited.

### *1.4.3.3 Diagnostic approaches\*\*\**

The American College of Obstetricians and Gynaecologists recommends a twostep procedure for diagnosing GDM [3, 15]. If after 1 hour the blood glucose level is more than 7.8 mmol/L (140 mg/dL), a 100 g dose of glucose is given. The diagnosis of gestational diabetes is thus defined by a blood glucose level meeting or exceeding the cut-off values of at least two intervals:


One-step approach: a diagnostic 75-g OGTT is performed at the 24th–28th week of gestation without the prior 50-g GCT screening. The one-step approach can be applied to high-risk pregnant women with GDM, or pregnant women not previously diagnosed with overt diabetes in well-conditioned medical institutions.

Two-step approach: measure FPG (step 1). If FPG ≥5.1 mmol/L, GDM can be diagnosed; if 4.4 mmol/L ≤ FPG <5.1 mmol/L, diagnostic 75-g OGTT (step 2) is followed to diagnose GDM. Or perform an initial screening by measuring the plasma or serum glucose concentration after a 50-g GCT (step 1) and perform a diagnostic OGTT (step 2) on that subset of women exceeding the glucose threshold value on the GCT. If 50-g GCT ≥11.1 mmol/L, FPG is performed to diagnose GDM; if the FPG value is normal, 75-g OGTT should be performed as soon as possible.

The cut-off points of glucose values of 75-g OGTT: 0 h, 5.1 mmol/L; 1 hour, 10.0 mmol/L; 2 hours, 8.5 mmol/L. The diagnosis of GDM can then be made when any one value is met or exceeded.

## **1.5 Complications of diabetes in pregnancy**

Diabetes in pregnancy is associated with a number of complications in the mother and unborn foetus [16]. These complications can also extend beyond the duration of pregnancy. These complications can be divided into maternal complications and foetal complications.

## *1.5.1 Maternal complications*

## *1.5.1.1 Miscarriage*

Statistics show that women with PDM have a 9–14% rate of miscarriage [16]. Available data further suggests that there is a strong association between the degree of glycaemic control before pregnancy and the rate at which miscarriage occurs in women with PDM. In cases of more long-standing disease (>10 years) with poor control, the miscarriage rates can reach as high as 44%. Thankfully, the miscarriage rate normalises when glycaemic control is optimal.
