Gestational diabetes mellitus (GDM) is a form of diabetes that can develop during pregnancy, usually toward the end of the second trimester. Having GDM increases the risk of complications during the rest of the pregnancy. Women with GDM are more likely to develop pre-eclampsia (a combination of 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 2 diabetes in the future. There is strong evidence that treatment of 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, frequent urination or fatigue. The two main approaches to screening approaches are 'universal' where all women undergo a screening test for GDM; and a selective approach 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 of four trials involving 3972 women found that there is little high-quality evidence on the effects of screening for GDM on health outcomes for mothers and their babies. Further research is required to see which recommendations for screening practices for gestational diabetes are most appropriate.