A Glucose Tolerance Test (GTT) is a blood test that is used to diagnose impaired glucose tolerance and gestational diabetes during pregnancy. The test measures your body’s ability to maintain a normal blood glucose (sugar) level. Glucose screening and glucose tolerance testing can help you detect gestational diabetes early, and give you a chance to minimize the risks of this condition. It is crucial for the mum and the baby because untreated or badly controlled gestational diabetes can cause polyhydramnios (excess amounts of amniotic fluid in the water bag), abnormal growth of baby (very big or small babies), linked to 20% of high-blood pressure, as well as increase risk of jaundice after delivery. It can also lead to premature delivery, traumatic delivery (if the baby is too big) and low blood sugar level of the baby after delivery, which can then affect respiration and feeding (suckling). Routine screening is usually done at 24 to 28 weeks of gestation.