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Gestational Diabetes

Transient gestational diabetes usually appears during the last six months of pregnancy and takes the form of either impaired glucose tolerance or diabetes. IGT maybe suspected if a random reading of fasting plasma glucose between 6 and 8 mmol/1 is obtained. Diabetes may be suspected if a random fasting plasma glucose reading greater than 8 mmol/1 is obtained. However, diagnosis depends upon a 75 g Oral Glucose Tolerance Test being performed. IGT is then diagnosed if a glucose reading between 9 and 11 mmol/1 is obtained, two hours after the glucose challenge. Diabetes is diagnosed if the reading is greater than 11 mmol/1. There are a number of risk factors for the development of gestational diabetes. These include:

being overweight or obese and excessive weight gain during pregnancy
older mother
previous glucose intolerance
previous birth of large baby
belonging to a high-risk ethnic group
previous history of hydramnios, an abnormal condition during pregnancy in which an excess quantity of amniotic fluid is produced
previous glycosuria during pregnancy on two or more separate times of testing.

Screening for gestational diabetes takes the form of periodic testing of urine for the presence of glucose and also blood testing, at the first ante-natal visit and then repeated between 24 and 28 weeks into the pregnancy. If there are any indications of diabetes, an OGGT will be carried out to confirm the diagnosis. In obese women or those who are gaining a lot of weight, calorie restriction will be suggested and may be sufficient to control IGT in pregnancy. However, 30 per cent of women with gestational diabetes need insulin to control their condition. oral antidiabetic drugs are not a recommended treatment during pregnancy.

A woman with insulin-treated gestational diabetes requires special care during labour and the birth may need to be induced at 38 to 39 weeks if it has not taken place naturally. Normal delivery is usually possible but since there is an increased likelihood of an extra large baby (macrosomia), a caesarean section may be required. After delivery, all but a small proportion (fewer than 10 per cent) of mothers who have gestational diabetes revert to glucose tolerance within the normal range. Insulin is usually stopped soon after the birth. An OGGT is generally carried out at the six week post-natal check up to ensure that diabetes has resolved. Affected women are advised on the importance of weight control, diet, exercise, and so on, in order to lessen the risk of development of Type 2 diabetes.