Gestational diabetes mellitus (GDM) is a form of diabetes that can develop during pregnancy. Having GDM increases the risk of complications during the rest of the pregnancy for the mother and her baby. Women with GDM are more likely to develop pre-eclampsia (high blood pressure and protein in the urine) and require a caesarean section. For the baby, potential problems include the baby growing larger than it normally would, causing difficulties with birth. The baby can also have low blood sugar levels after birth. Although GDM usually resolves following birth, both mother and child are at risk of developing type II diabetes in the future. There is strong evidence that treating GDM is beneficial and improves health outcomes.
It may therefore help if pregnant women are screened to identify as many as possible of those who do have GDM before they have symptoms, such as excessive thirst or urination, or fatigue. The two main approaches to screening are 'universal' where all women undergo a screening test for GDM; and 'selective' where only those women at 'high risk' are screened. The main risk factors are maternal age, high body mass index, family history and cigarette smoking. The different screening strategies used around the world to identify women with GDM include identifying women based on their risk factors, a blood sugar test one hour after a 50 g glucose drink, and random blood sugar measurements. It is however unclear whether screening for GDM leads to better health outcomes and if so, which screening strategy is the most appropriate.
This review included four trials involving 3972 women and their babies, and found that there is little high-quality evidence on the effects of screening for GDM on health outcomes for mothers and their babies. One trial compared risk factor screening with universal screening, and three trials evaluated different methods of administering a 50 g glucose load (the glucose load is used during the screening test). In one trial, women who were in the universal screening group were more likely to be diagnosed with GDM compared with women in the high-risk screening group. However, this trial was not of high quality. Few other differences between groups were shown in any of the trials. Further research is required to see which recommendations for screening practices for GDM are most appropriate.