Endocrine disorders in pregnancy

Published on 10/03/2015 by admin

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Last modified 10/03/2015

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Chapter 16 Endocrine disorders in pregnancy

DIABETES MELLITUS

During pregnancy the placenta secretes substances that have an anti-insulin action, including human placental lactogen (hPL), progesterone, human chorionic gonadotrophin (hCG), cortisol and cytokines including TNFα. If the maternal β islet cells are unable to produce the additional insulin required to counteract this effect, the woman will develop hyperglycaemia (gestational diabetes). The incidence of glucose intolerance during pregnancy reflects the background prevalence of type 2 diabetes and impaired glucose tolerance. In some communities this reaches 10% or more using the current criteria.

As maternal glucose, but not insulin, can readily cross the placenta, the fetal pancreas will secrete additional insulin if there is maternal hyperglycaemia. This fetal hyperinsulinaemia can result in macrosomia, polycythaemia, impaired lung maturation, neonatal hypoglycaemia, jaundice, hypocalcaemia and hypomagnesaemia. Offspring may develop glucose intolerance in childhood and they are more prone to adult obesity.

Maternal hyperglycaemia, at the time of conception and during embryogenesis, can cause major fetal abnormalities (neural tube defects, cardiac abnormalities, skeletal abnormalities) and increase the risk of miscarriage.

Detection of gestational diabetes

Routine screening of all pregnant women for hyperglycaemia should no longer be considered controversial as two large RCTs have both shown benefit from treating gestational diabetes and the results from the Hyperglycaemia and Adverse Pregnancy Outcome study (HAPO) are being used to define the diagnostic criteria that predict an adverse perinatal outcome. The two currently most widely used criteria are detailed in Table 16.1.

Table 16.1 The diagnosis of gestational diabetes

Women who are more likely to develop gestational diabetes are those who have a previous history of gestational diabetes; who suffered an intra-uterine death late in pregnancy; who have a close family member or members who are diabetic; who are from an ethnic group with a high prevalence of type 2 diabetes; who are older than 30 years, who have persistent glycosuria, or where there is fetal macrosomia should be tested early in pregnancy, ideally before they conceive. If the test is negative they should be retested at the beginning of the third trimester when all women should be screened.

Management of diabetes

Pre-pregnancy advice

Ideally, women who are known to be diabetic and women who have had gestational diabetes should be seen before they become pregnant. This consultation offers the opportunity to explain to the woman the reasons for meticulously maintaining her blood glucose at normal levels before conception, and to ensure dietary advice has included taking folic acid to reduce the risk of neural tube defects. Each woman needs to be assessed for the presence of any complications associated with diabetes, such as diabetic retinopathy and nephropathy. Women who are taking oral hypoglycaemic agents should preferably be changed to insulin therapy.

Pregnancy

In pregnancy the key principles of management include:

• A multidisciplinary team, including an endocrinologist, a diabetic educator, a dietitian, a neonatologist and obstetrician, is desirable for management.

• Euglycaemia should be maintained throughout, with fasting blood glucose less than 5.0 mmol/L and if measured 1 hour after eating less than 8 mmol/L and 2 hours after eating less than 7 mmol/L.

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