Pregnancy in Association with Diabetes Mellitus

Abstract

That the problems presented by the association of pregnancy and diabetes mellitus is of absorbing interest is proved by the recent spate of reviews and reports on the subject. Despite this evidence of continuing thoughtful study these problems remain largely unsolved and, in defiance of considerable growth of knowledge, much remains obscure.The facts are now well known, but the explanation underlying them, together with the best means of meeting them, is in dispute. These facts must bear repetition for the sake of clarity.Prior to the discovery of insulin the combination was but rarely seen, on two accounts: few young diabetic girls survived to childbearing age; and amenorrhoea and infertility of nutritional or endocrine origin afflicted those who did. With the successes achieved by insulin, and especially since long acting insulins became available, carrying their much improved degree of control, both these influences have been abolished. Nowadays, though diabetic fertility is not up to normal, these pregnancies account for something like one in three hundred. That they are not more frequent depends on the incidence of -diabetes mellitus falling most heavily on women past childbearing age.Some time after insulin came into general use, it became clear that pregnancy in diabetics ran a distinctive abnormal course. Later still the pooling of individual experiences led to widespread recognition of a specific problem, the outstanding features being: for the mother, a liability to toxaemia and to spontaneous premature delivery of an apparently post-mature infant; for the foetus a tendency to die in utero in the last few weeks of pregnancy or in the first two days of neonatal'life and in each case to be overweight. Together these made for a stormy pregna'ncy, a difficult labour and, most important, the persistence of a foetal mortality rate of about 50 per cent., little if any better than that of pre-insulin experience.The next advance was the recognition that women destined to develop diabetes were subject to identical obstetric and foetal accidents, and that the incidence and severity of these increased as the date of delivery advanced towards the date of onset of the disease. Thus, in the five years immediately antecedent to the diagnosis of diabetes the foetal death rate equals that of overt diabetics, while in the twenty or more years preceding, it is very much less, yet significantly more than the normal.Following the facts further, the influence of the pregnancy on the diabetes deserves first consideration. Two fundamental changes explain the instability and tendency to the more serious complications often encountered. First, lowering of the renal threshold common to many pregnant women is not only much more common in diabetics, but much more severe towards the end of such a pregnancy. Thus results a glycosuria out of all proportion to blood sugar levels. Second, there is a steady' deterioration of carbohydrate tolerance throughout pregnancy, again most obvious in the last three months and displayed as an incre...