17.2 Diabetes in pregnancy

Diabetes is one of the more difficult conditions to manage, under the conditions for which we write, especially in pregnancy. Insulin supplies are likely to be a major problem, with patients dying when their supplies are interrupted. Even where care is good, it may only be the teachers and health workers who are sufficiently motivated and educated to manage their diabetes well enough to survive for long. Here is what you should do, with some advice as to what you can do, if your facilities are so limited that you can only measure the blood glucose exceptionally, if at all. If so, you will not be able to control a patient’s diabetes well enough to prevent its adverse effects on her or her baby, but you should be able to keep her out of coma.

Pregnancy and diabetes adversely affect one another, and the more complicated or long-standing the diabetes, the stronger the effect. Diabetes increases maternal mortality 10 times, as the result of ketoacidosis, hypoglycaemia, and infection. A mother is also at increased risk from polyhydramnios (50), gestational hypertension (3), and infection (especially pyelonephritis). Fortunately, pregnancy will not usually harm her health in the long term. If however she has retinopathy, this may get worse during pregnancy, although it may improve afterwards; uropathy on the other hand may worsen irreversibly. Her baby is at increased risk from sudden intrauterine death (usually at 36 to 38 weeks), fetal macrosomia (excessive size), neonatal hypoglycaemia (19.12), prematurity (particularly hyaline membrane disease), and congenital malformations (3). Careful diabetic management reduces these risks.

At the start of pregnancy she can have: (1) Type One diabetes (IDDM, insulin-dependent diabetes mellitus). (2) Type Two diabetes (NIDDM non-insulin-dependent diabetes mellitus). This is uncommon in women of childbearing age in Africa, and is more common in obese mothers in India and the Middle East. We shall not make any further reference to Types One and Two diabetics; it is the insulin-dependent Type One patients who are important. (3) Impaired glucose tolerance. However, following Chalmers, who concluded that: ’Except for research purposes, all forms of glucose tolerance testing should be stopped (in pregnancy)’, we say nothing more about it here. (4) Renal glycosuria, which is a lowered renal threshold to glucose, and is harmless. If diabetes resolves after pregnancy, it is said to have been ’gestational’.

About 1% of women have glucose in their urine when they are fasting. Most of them have renal glycosuria, and a few have diabetes.

Although testing the urine for glucose in early pregnancy picks up all cases of diabetes, it is an imperfect screening method because it picks up many harmless cases of renal glycosuria. Glucose in the urine may vary greatly from day to day during pregnancy, so that a patient may have glycosuria on one visit and not on the next. Also, testing the urine is also a poor way of monitoring the insulin requirements of a pregnant diabetic, especially after 16 weeks.

Unfortunately, testing the urine for glucose is the only practical screening test, so test the urine of all mothers, and investigate them as best you can.

Diabetic babies tend to be large, so don’t let a mother become overdue. Ideally, she should deliver at 36 to 38 weeks. If she is a multip, you can usually induce her fairly easily.