Once diet alone can no longer consistently ensure fasting glucose values below 5.5 mmol/l and a 1 h post-prandial value below 7 mmol/l, the introduction of insulin should be considered (63). It is important to recognise that a small proportion of women will require insulin early in pregnancy and not to assume dietary non-compliance (92). Those requiring insulin are the most metaboli-cally compromised and tend to have both the highest perinatal complications and the fastest deterioration to diabetes after pregnancy (93). Insulin is also occasionally introduced in later pregnancy for obstetric rather than glycaemic reasons; this might occur for accelerated foetal growth or unexplained polyhydramnios (94).
It is important to stress that once insulin is introduced for the management of GDM the dietary management remains equally important. The need to limit weight gain remains for obese women who now need to balance this with having sufficient carbohydrate snacks throughout the day to prevent hypoglycaemia. Although short periods of hypoglycaemia are not detrimental to the foetus they are unpleasant for the woman and frequently result in sudden rises of blood sugar due to the action of counter-regulatory hormones and the consumption of sugary drinks. Frequent episodes of hypoglycaemia often result in women chasing these high-rebound glucose levels by increasing their insulin dosage, which can result in further hypoglycaemic attacks and unnecessary weight gain.
When starting on insulin women should be advised to take low glycaemic index carbohydrates at meal times and for snacks between meals and before bed. Fruit is ideal for snacks as it is low in fat and calories. Fruit, by being slowly absorbed, reduces the risk of hypoglycaemia while allowing postprandial glucose levels to be lowered without having to increase the insulin dose.
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