Evaluation of the 50g-glucose challenge test in 1416 pregnancies

Introduction: Disorders of maternal carbohydrate metabolism are among the most common diseases in pregnancy and are related with high risks for mother and child. The diagnosis is made by biochemical parameters, for example a 3-hour oral glucose tolerance test (OGTT). Certainly different protocols exist about the kind of carbohydrate donators and the cut-off values. However, this led to worldwide differences in the incidence of gestational diabetes mellitus (GDM) between 1-12%. For an early detection and therapy the 50 g-glucose challenge test is used in many countries as recommended by the Second International Workshop Conference (1985). This test should be carried out between the 24th acid 28th week of gestation, independent of previous meal and time of the day. If the plasma glucose value after 1 hour later is equal to or greater than 140 mg/dl, an OGTT should be performed. Material and methods: In this prospective study we evaluated sensitivity and specificity of this challenge test on 1416 unselected pregnant women in the third trimester. We tried to find answers to following questions: 1. Does the incidence of GDM justify a general screening? 2. Can we show clinical consequences on failing therapy? 3. Do patients with an impaired glucose tolerance (IGT) have more complications? A diagnosis of GDM was made if two or three of the following Values were met or exceeded: fasting: 90 mg/dl, 1 hour: 165 mg/dl, 2 hours: 145 mg/dl. If only one value was in excess we diagnosed an IGT. Therefore, we checked on the records of all patients to detect patients who developed abnormal glucose values later in gestation, Results: 26.3% (372/1416) of the patients had a screening value higher than 140 mg/dl. 264 of them had an OGTT, 108 of the patients were non-compliant for different reasons. We detected a GDM in 38% (100/264) of the patients. 27% (71/164) had an IGT. 50 patients with normal screening underwent an OGTT because of clinical findings (glucosuria, macrosomia, abnormal weight gain). 14% (7/50) were classified as GDM. The overall incidence of GDM is 8.2% (107/1308). The positive predictive value is 37.9%. Should all patients with GDM be detected during gestation, the sensitivity of this test would be 93.5% and the specificity 86.3%. We observed variation of these values in different nationals. We formed 6 groups from the observed patients (control group, IGT, GDM, patients with abnormal screening and normal OGTT, patients with normal screening and abnormal OGTT, untreated patients). In these groups we found differences in anthropometric data, hypertension (untreated patients vs. control group), the rate of vaginal-operative deliveries (IGT vs. control group) and the caesarean section rate (untreated patients vs. control group). In addition, we proved deviations between these groups in birthweights and transfer of the newborn to the pediatric ICU. Conclusions: Detected and treated GDM have a similar outcome than the control group. Untreated women with an exceedingly high challenge test result without diagnosis and treatment have a higher rate of hypertension, caesarean section and transfer to the pediatric ICU. Our results point to the necessity of a glucose challenge test in Germany. There is no reason to withhold this useful test from German pregnant women. However, we have shown that patients with an IGT require more rigorous control.