- Diagnosis and Classification of Diabetes
- Initial Assessment and Criteria for Specialist Referral
- Glycaemic Control in Type 2 Diabetes - Oral Hypoglycaemic Agents
- Indications for Insulin in Type 2 Diabetes
- Hypertension
- Dyslipidaemia
- Aspirin Therapy in Diabetes
- Retinopathy
- Nephropathy
- Neuropathy and Foot Ulcers
- Sexual Dysfunction in Men
- Diabetes in Pregnancy and Pre-conception Guidance
12. Diabetes in Pregnancy and Pre-conception Guidance
Pregnancy in diabetes is associated with an increase in risk to both the fetus and the mother. There is, for example, an increased incidence of congenital anomalies and spontaneous abortions in women who are in poor glycaemic control during the period of fetal organogenesis, which is nearly complete at seven weeks post-conception. A consequence of poor glycaemic control in pregnant women with diabetes is fetal macrosomia, which leads to difficult deliveries, an increased need for caesarean delivery, and an increase in fetal morbidity. The macrosomia is caused by fetal hyperinsulinaemia. This emphasises the importance of tight glycaemic control both before conception so that and throughout pregnancy. Despite the clear benefits to the fetus of strict glycaemic control, there are two potential hazards in the mothers: hypoglycaemia and some worsening of diabetic retinopathy. Major complications of hypoglycaemia can usually be prevented with careful monitoring and education of the mother.
Treatment – There are several components to the treatment of diabetes in pregnant women: careful monitoring of blood glucose; administration of insulin; and diet. Attention must also be paid to obstetric surveillance and treatment during labour and delivery.
Insulin regimen – Most women with type 1 diabetes require at least four injections of insulin per day. Total daily insulin requirements usually vary considerably during gestation. After an early rise in insulin requirements between weeks 3 and 7, there often is a significant decline between weeks 7 and 15, followed by a rise during the remainder of pregnancy.
Women with type 2 diabetes also should be treated with insulin for blood glucose control, preferably started during the preconception period. During the first trimester, insulin requirements are similar in women with type 1 and type 2 diabetes. However, as the pregnancy proceeds into the third trimester, insulin requirements increase proportionately more in women with type 2 than type 1 diabetes. Measures that ameliorate insulin resistance, such as avoiding excessive weight gain and moderate low-impact exercise, can be expected to improve glycaemic control.
Oral hypoglycaemic drugs should not be given to pregnant women with established diabetes because the drugs may have teratogenic effects in early pregnancy and they do not provide strict glycaemic control. When metformin is used to induce ovulation in patients with the polycystic ovary syndrome and insulin resistance, it should be stopped as soon as pregnancy is diagnosed.
Screening and diagnosis of gestational diabetes mellitus
Pregnancy is a diabetogenic state manifested by insulin resistance and hyperinsulinaemia. The resistance stems from the placental secretion of diabetogenic hormones including growth hormone, corticotropin-releasing hormone, placental lactogen, and progesterone. Gestational diabetes mellitus occurs when a woman's pancreatic function is not sufficient to overcome the insulin resistance created by the anti-insulin hormones and the increased fuel consumption necessary to provide for the growing mother and fetus. The diagnosis and treatment of gestational diabetes are important because of the association of poor control with increases in the incidence of the following:
- Pre-eclampsia
- Polyhydramnios
- Fetal macrosomia
- Birth trauma
- Operative delivery
- Neonatal metabolic complications (hypoglycaemia, hyperbilirubinaemia, hypocalcaemia, and erythraemia)
- Perinatal mortality
- Later development of diabetes mellitus in the mother.
Risk Factors and Selection of Women for Screening – Clues that a pregnant woman may be at high risk for gestational diabetes are: - A family history of diabetes, especially in first-degree relatives
- Obesity
- Age greater than 25 years
- A previous large baby (>4.1 kg)
- History of abnormal glucose tolerance
- Member of an ethnic group with a higher than normal rate of type 2 diabetes
- A previous unexplained perinatal loss or birth of a malformed child
- The mother was large at birth (>4.1 kg).
Using these historical risk factors alone will miss approximately one-half of women with GDM. There is little consensus regarding whom to test or how to test for gestational diabetes. Screening is usually limited to women with risk factors for gestational diabetes and performed at 24 to 28 weeks of gestation. However, it can be done as early as the first prenatal visit if there is a high degree of suspicion that the pregnant woman has undiagnosed type 2 diabetes. Screening tests include post-prandial blood tests followed by an oral glucose tolerance test (OGTT).
Identifying women with gestational diabetes mellitus is important because appropriate therapy can decrease fetal and maternal morbidity, particularly macrosomia and stillbirth. An effective treatment regimen consists of dietary therapy, self-blood glucose monitoring, and the administration of insulin if the target blood glucose values are not met with diet alone.
Glucose Monitoring And Goal Concentrations – Women with gestational diabetes should measure blood glucose at home aiming for fasting blood glucose concentrations <5 mmol="" and="" post-prandial="" blood="" glucose="" concentrations="" mmol="">
HbA1c values are not sufficiently sensitive to aid in screening for gestational diabetes but are helpful in assessing glycaemic control during pregnancy. Approximately 15% of women with gestational diabetes require insulin therapy to prevent stillbirth and macrosomia.
Post-Partum Concerns And Future Risk – Nearly all women with gestational diabetes are normoglycaemic after delivery. However, they are at risk for gestational diabetes, impaired glucose tolerance, and overt diabetes. Approximately 50% of women will have gestational diabetes in a subsequent pregnancy. Gestational requirement for insulin, maternal obesity, high fasting blood glucose concentrations during pregnancy and early postpartum, and early gestational age at the time of diagnosis are risk factors for impaired glucose tolerance and even overt diabetes at a later date. Parity, habitus, large birth weight, and diabetes in a first-degree relative are less correlated with later diabetes.
Approximately six to eight weeks after delivery, or shortly after cessation of breast-feeding, all women with previous gestational diabetes should undergo an oral glucose tolerance test. A postpartum woman with normal glucose tolerance should be counselled regarding her risk for developing gestational diabetes in subsequent pregnancies and possible type 2 diabetes in the future. Weight loss and exercise are clearly beneficial and long-term follow-up is essential. Preferably, fasting plasma glucose should be measured yearly, with appropriate intervention if the value is greater than 6.0 mmol/L.
Type 1 Diabetes
Type 1 diabetes can present during pregnancy and may be mistaken for gestational diabetes. Clues to the presence of type 1 diabetes include:
- Lean women
- Diabetic ketoacidosis during pregnancy
- Severe hyperglycaemia during pregnancy requiring large doses of insulin
- Post-partum hyperglycaemia
Measurements of serum anti-islet cell antibodies may be helpful for identifying type 1 diabetes in pregnant women. Women who have these antibodies during pregnancy should be advised to continue self-blood glucose monitoring postpartum to document persistent hyperglycaemia.