Glycemic targets in pregnancies affected by diabetes: historical perspective and future directions

The definition of optimal glycemic control in pregnancies affected by diabetes remains enigmatic. Diabetes phenotypes are heterogeneous. Moreover, fetal macrosomia insidiously occurs even with excellent glycemic control. Current blood glucose (BG) targets (FBG ≤95, 1-h post-prandial <140, 2 h <120 mg/dL) have improved perinatal outcomes, but arguably they have not normalized. The conventional management approach has been to replicate a pattern of glycemia in normal pregnancy. Although these patterns are lower than previously appreciated, a randomized controlled trial (RCT) has never compared current vs. lower glucose targets powered on maternal/fetal outcomes. This paper provides historical context to the current targets by reviewing evidence supporting their evolution. Using lower targets (FBG <90, 1 h <122, 2 h <110, mean BG ≤95 mg/dL) may help normalize outcomes, but phenotypic differences (type 1 vs. type 2 vs. gestational diabetes) might require different glycemic goals. There remains a critical need for well-designed RCTs to confirm optimal glycemic control that minimizes both small for and large for gestational age across pregnancies affected by diabetes.

Prediabetes and the big baby

The concept of prediabetes has come to the fore again with the worldwide epidemic of Type 2 diabetes. The careful observations of W. P. U. Jackson and his colleagues in Cape Town, South Africa 50 years ago still deserve attention. Maternal hyperglycaemia cannot be the only cause of fetal macrosomia, and the pathophysiological reason for the unexplained stillbirth in late diabetic pregnancy still eludes us. The biochemical concepts of 'facilitated anabolism' and 'accelerated starvation' were developed by Freinkel as explanations of the protective mechanisms for the baby during the stresses of pregnancy. Some of these nutritional stresses may also occur in the particular form of early childhood malnutrition known in Africa as kwashiorkor, where subcutaneous fat deposition, carbohydrate intolerance, islet hyperplasia and sudden death may follow a period of excess carbohydrate and deficient protein intake. Different feeding practices in different parts of the world make comparisons uncertain, but there is evidence for insulin resistance in both the macrosomic fetus of the hyperglycaemic mother and in the child with established kwashiorkor. These adaptive changes in early development may play both a physiological and a pathological role. Worldwide studies of hyperglycaemia in pregnancy are gradually establishing acceptable diagnostic criteria, appropriate screening procedures and an evidence base for treatment. Nevertheless the challenge of prediabetes and the big baby is still with us--in Jackson's words--'diabetes mellitus is a fascinating condition-the more we know about it the less we understand it'.

[Pregnancy in diabetic women--past and today]

The discovery of insulin in 1921 and introducing insulin into a clinical practice gave an unique opportunity to treat people suffering from a type 1 diabetes successfully. Prior to this success, pregnancy in diabetic women was extremely rare and most of cases resulted in stillbirth and fatal outcome for mother. After the introduction of insulin into therapy of pregnant women with diabetes, a permanent improvement in neonatal and maternal outcome has been noted. However, a diabetic pregnancy still constitutes a high risk pregnancy, requiring a targeted, highly specialized control of women and fetus. This review presents problems concerning diagnose, treatment and outcome of diabetic pregnancy throughout the XXth century.

Dr Priscilla White (1900-1989) of Boston and pregnancy diabetes

A woman doctor in a man's world, Priscilla White dedicated her whole life to the care of diabetic women during pregnancy and to children with this condition. She emphasised the importance of close supervision during pregnancy by a small obstetric and diabetic team. Her classification of diabetes in pregnancy was widely accepted. During her long career she pioneered a number of advances in this field and witnessed a remarkable fall in maternal and perinatal mortality.

Maternal blood glucose and the baby. The origins of the hyperglycaemia and pregnancy outcome study The Scott-Heron Lecture at the Royal Victoria Hospital--17 January 2001

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Pregnancy in women with diabetes mellitus. The beginning

Before the discovery of insulin in 1921, pregnancies in women with diabetes mellitus were uncommon. Most patients succumbed to ketoacidosis within 1 to 2 years after diagnosis. Insulin therapy restored the fertility of these women, and maternal deaths were nearly eliminated; however, the perinatal mortality rate remained high. Elective preterm deliveries were planned to reduce the stillbirth rate, often resulting in neonatal deaths from respiratory distress syndrome. Furthermore, women with more severe disease were able to become pregnant with a risk of complications due to preeclampsia.

A story of two miracles: the impact of the discovery of insulin on pregnancy in women with diabetes mellitus

Before the discovery of insulin in 1921, pregnancies in women with diabetes mellitus were a rarity because most reproductive-age patients died soon after diagnosis of this illness. In the limited number of pregnancies reported in the pre-insulin era, both perinatal and maternal mortality were approximately 50%, with stillbirths being the primary cause of perinatal deaths. Insulin treatment restored the fertility of women with diabetes and was associated with a marked reduction in maternal mortality. Women with more severe disease had the opportunity to become pregnant; however, their pregnancies frequently resulted in neonatal death due to prematurity. Therefore, perinatal mortality was not substantially reduced.

[Insulin-dependent diabetes and pregnancy. A model of coordinated approach]

A historical account of the relation between diabetes and pregnancy is followed by the presentation of a personal series of 10 insulin-dependent diabetic pregnant women (3 White's class B, 2 class C, 3 class D and 2 class F/R) treated in accordance with a newly applied quarterly and fortnightly protocol. Nearly normal blood sugar (HbA1 maintained around 8% in the second and third trimester) was achieved through home blood glucose self-monitoring, in keeping with the Karen Bruni Centre's educational programme. This includes self-management of intensified insulin treatment in the form of 2-3 injections per day (Monotard MC and HM, Actrapid MC and HM), as well as the use of Novo Pen (100 U/ml Actrapid HM) for supplementary insulinisation. Average insulin initial dose: 0.51 U/Kg/day (range 0.2-0.7); final dose 0.83 U/Kg/day (range 0.6-1.2). Delivery was by caesarean section on obstetric indication: 9 at the 36th week, 1 at the 34th for trisymptomatic gestosis. There were no foetal nor neonatal death. All children were subjected to intensive neonatological care. There were 3 cases of macrosomia and 1 tetralogy of Fallot, which followed a benign course. Despite their absence of statistical value, these data show that optimised multidisciplinary treatment can be of utility in preventing neonatal morbidity and mortality in an insulin-dependent diabetic pregnancy. They also indicate that a coordinated treatment model can equally be put into effect even in a non centralised structure, provided certain facilities exist: in our case, voluntary support on the part of Karen Bruni Diabetic Association, obstetric interest in diabetology and a neonatological background for treatment of the offspring of diabetic mothers. Lastly, this series substantiate the effectiveness of the programme of self-checking and self-management of diabetes in the accomplishment of "optimised" blood glucose control and containment of costly hospitalisation at the time of delivery.

Nutritional management of pregnancy complicated by diabetes: historical perspective

The important role of diet in the management of pregnancies complicated by diabetes has been recognized since the nineteenth century. In this historical review we have traced the evolution of the diabetic diet from the pre-insulin era, when diabetic pregnancies were not only rare, but accompanied by high maternal mortality and fetal loss to 1981, when the nutritional management of carbohydrate intolerance during gestation is again raising provocative questions. Our recent understanding of diabetes as a heterogeneous syndrome, the 1979 dietary guidelines of the American Diabetes Association (ADA), and the 1980 revised Recommended Dietary Allowances (RDA) for pregnant and lactating women are summarized as representative of the current approach to the nutritional management of diabetic pregnancies. Many questions remain unanswered. These include the hundred-year-old debate concerning the optimal amount of carbohydrate in the diabetic diet, the possible beneficial role of large amounts of dietary fiber, and the nagging concern about total caloric intake in type I insulin-dependent diabetes mellitus (IDDM) versus type II non-insulin-dependent diabetes mellitus (NIDDM) pregnant diabetic women. We suggest that nutritional counseling during gestation in the future may need to be more highly individualized as metabolic distinctions between different types of patients with carbohydrate intolerance are more clearly delineated.