Diabetes mellitus in pregnancy: an update on the current classification and management

BACKGROUND

Diabetes mellitus is a common medical disorder in pregnancy. It contributes particularly to perinatal morbidity/mortality, and maternal morbidity. This review aims at improving maternal and neonatal health care especially in Sub-Saharan Africa by improving the knowledge of health practitioners on current evidences in the classification and management of diabetes mellitus in pregnancy.

METHODS

Relevant texts as well as online data bases including Pubmed, Google scholar, and African journal online, were searched for literatures related to the subject.

RESULTS

Classification of diabetes in pregnancy has been revised to reflect the various aetiological factors. Also, the diagnostic value of fasting plasma glucose has been lowered to mark the point at which dramatic increase in the microvascular complications of diabetes mellitus occurs. Morbidity and mortality associated with the condition would be reduced through proper management that involves preconception care, early antenatal booking, dedicated multidisciplinary antenatal care, and delivery in a center with neonatal facility. Furthermore, some oral glucose lowering agents have shown some safety after the first trimester and they have been found to give comparable result to insulin therapy.

CONCLUSION

The classification of diabetes mellitus in pregnancy has been revised. Its optimal management should involve multi-disciplinary inputs and may include oral hypoglycaemic agents. Knowledge of these by clinicians would improve maternal and neonatal health.

Impact of ethnicity on gestational diabetes identified with the WHO and the modified International Association of Diabetes and Pregnancy Study Groups criteria: a population-based cohort study

OBJECTIVE

The International Association of Diabetes and Pregnancy Study Groups (IADPSG) recently proposed new criteria for diagnosing gestational diabetes mellitus (GDM). We compared prevalence rates, risk factors, and the effect of ethnicity using the World Health Organization (WHO) and modified IADPSG criteria.

METHODS

This was a population-based cohort study of 823 (74% of eligible) healthy pregnant women, of whom 59% were from ethnic minorities. Universal screening was performed at 28±2 weeks of gestation with the 75 g oral glucose tolerance test (OGTT). Venous plasma glucose (PG) was measured on site. GDM was diagnosed as per the definition of WHO criteria as fasting PG (FPG) ≥7.0 or 2-h PG ≥7.8 mmol/l; and as per the modified IADPSG criteria as FPG ≥5.1 or 2-h PG ≥8.5 mmol/l.

RESULTS

OGTT was performed in 759 women. Crude GDM prevalence was 13.0% with WHO (Western Europeans 11%, ethnic minorities 15%, P=0.14) and 31.5% with modified IADPSG criteria (Western Europeans 24%, ethnic minorities 37%, P< 0.001). Using the WHO criteria, ethnic minority origin was an independent predictor (South Asians, odds ratio (OR) 2.24 (95% confidence interval (CI) 1.26-3.97); Middle Easterners, OR 2.13 (1.12-4.08)) after adjustments for age, parity, and prepregnant body mass index (BMI). This increased OR was unapparent after further adjustments for body height (proxy for early life socioeconomic status), education and family history of diabetes. Using the modified IADPSG criteria, prepregnant BMI (1.09 (1.05-1.13)) and ethnic minority origin (South Asians, 2.54 (1.56-4.13)) were independent predictors, while education, body height and family history had little impact.

CONCLUSION

GDM prevalence was overall 2.4-times higher with the modified IADPSG criteria compared with the WHO criteria. The new criteria identified many subjects with a relatively mild increase in FPG, strongly associated with South Asian origin and prepregnant overweight.

Development and evaluation of a standardized registry for diabetes in pregnancy using data from the Northern, North West and East Anglia regional audits

OBJECTIVES

To develop and evaluate a standardized data set for measuring pregnancy outcomes in women with Type 1 and Type 2 diabetes and to compare recent outcomes with those of the 2002-2003 Confidential Enquiry into Maternal and Child Health.

METHODS

Existing regional, national and international data sets were compared for content, consistency and validity to develop a standardized data set for diabetes in pregnancy of 46 key clinical items. The data set was tested retrospectively using data from 2007-2008 pregnancies included in three regional audits (Northern, North West and East Anglia). Obstetric and neonatal outcomes of pregnancies resulting in a stillbirth or live birth were compared with those from the same regions during 2002-2003.

RESULTS

Details of 1381 pregnancies, 812 (58.9%) in women with Type 1 diabetes and 556 (40.3%) in women with Type 2 diabetes, were available to test the proposed standardized data set. Of the 46 data items proposed, only 16 (34.8%), predominantly the delivery and neonatal items, achieved ≥ 85% completeness. Ethnic group data were available for 746 (54.0%) pregnancies and BMI for 627 (46.5%) pregnancies. Glycaemic control data were most complete-available for 1217 pregnancies (88.1%), during the first trimester. Only 239 women (19.9%) had adequate pregnancy preparation, defined as pre-conception folic acid and first trimester HbA(1c) ≤ 7% (≤ 53 mmol/mol). Serious adverse outcome rates (major malformation and perinatal mortality) were 55/1000 and had not improved since 2002-2003.

CONCLUSIONS

A standardized data set for diabetes in pregnancy may improve consistency of data collection and allow for more meaningful evaluation of pregnancy outcomes in women with pregestational diabetes.

Progression of retinopathy in type 1 diabetic women during pregnancy

Progression of diabetic retinopathy (DR) occurs at least temporarily during pregnancy and postpartum. The pathogenetic mechanisms of DR progression during pregnancy are not fully understood. Several factors related to metabolic changes (hyperglycaemia), diabetes itself (duration of diabetes before conception, baseline status of DR), pregnancy physiology (hypervolaemia and hypercoagulation, impaired retinal autoregulation) and pregnancy complications (pre-eclampsia) seem to play important roles in the progression of DR during pregnancy. On the other hand, systemic angiopoietic and vasoactive factors seem to have minor role in the deterioration of DR during that time period. Good glycaemic control, normotension, lack of nephropathy as well as lack of pre-proliferative/proliferative changes of DR are good prognostic factors as regards the progression of DR during pregnancy. However, pregnancy seems to have no long-term detrimental effects as regards the progression of DR unless it has proceeded to pre-proliferative and proliferative phases.

Diabetes mellitus in pregnancy

This article reviews normal and abnormal carbohydrate metabolism in pregnancy, with an emphasis on the challenges that are faced by those who care for the pregnant woman who has hyperglycemia. The growing problem of type 2 diabetes in pregnancy, the controversial use of oral antihyperglycemic agents for the treatment of gestational diabetes, and the long-term issue of diabetes prevention in those whose hyperglycemia resolves postpartum are also addressed.

Macular capillary blood flow velocity by blue-field entoptoscopy in diabetic and healthy women during pregnancy and the postpartum period

PURPOSE

To study macular capillary blood flow velocity in diabetic and healthy women during pregnancy and the postpartum period.

METHODS

A prospective study of 46 pregnant women with insulin-dependent diabetes and 11 healthy pregnant women was performed. Macular capillary blood flow velocity was measured by blue-field entoptic simulation. Diabetic retinopathy was graded from colour fundus photographs.

RESULTS

In diabetic women, the macular capillary blood flow velocity was 0.94+/-0.27 mm/s (mean +/- SD) during the first trimester, 1.00+/-0.28 mm/s during the third trimester and 1.03+/-0.24 mm/s 3 months postpartum, compared with values of 0.71+/-0.20, 0.77+/-+/-0.20 and 0.82+/-0.19 mm/s, respectively, in healthy women (P=0.0026 between groups). Diabetic women with no or very mild retinopathy had lower macular capillary blood flow velocities than those with more severe retinopathy (P=0.0164), but higher velocities than healthy women (P=0.0167). An increase temporally from the first trimester to the postpartum period was observed in diabetic women (P=0.0294) but not in healthy (P=0.2449) women.

CONCLUSIONS

According to our study macular capillary blood flow velocity is higher in diabetic than in healthy women during pregnancy and the postpartum period. Further, capillary blood flow velocity seems to depend on the grade of retinopathy in pregnant diabetic women. These data support the concept that capillary hyperperfusion may play a role in the development of diabetic retinopathy during pregnancy.

Placental pathology in relation to the White's classification of diabetes mellitus

The objective of this study was to investigate various macroscopic and microscopic features of the placenta in pregnancies complicated by diabetes according to White's classification. A total of 148 placentas were studied. Sixty-five were from control patients and 83 from diabetic mothers. The diabetic mothers were further divided into three groups according to White's classification. There were 40 cases in White's group A and 36 cases in White's group B. There were 7 cases in White's groups C and D combined. Advanced maternal age and grandmultiparity were significantly higher in White A, White B and White C&D compared to the normal group. Mean weight of the mother was higher in White group A and group B compared to the control group and group C&D. The placental weight and neonatal weight were increased provided the diabetes was not complicated by vascular disease. With accompanying vascular disease the placental weight and neonatal weight were reduced compared to the controls. As a result of increased perinatal jeopardy the rate of operative delivery was higher in diabetic mothers. No major difference was observed in microscopic changes of placentas in different groups according to White's classification and the normal group.

[Diabetes and pregnancy. Past, present, and future]

After the discovery of insulin and during almost an half of a century, physicians and researchers apply their efforts in a better knowledge to reduce the perinatal mortality of the offspring of the diabetic mother. The optimisation of glucose control--the main key of the management of diabetic pregnancy--and the new methods of fetal and neonatal surveillance allowed that in the end of XX century the perinatal mortality were close to the general population. Nevertheless the perinatal morbidity is still elevated. Several studies suggest that fetal hyperinsulinism, consequence major of the abnormal intra uterine milieu of the diabetic mother, could be the cause of such morbidity at short and long term. In this paper, gestational diabetes is specially analysed. In spite of a large amount of studies, there is until know no diagnostic test that allows us to identify the pregnant women with a higher risk for a bad outcome namely, macrosomia and their consequences like caesarean section, traumatic delivery and neonatal complications. The ideal test should give that kind of information. Thus some methods of fetal surveillance had been proposed complementary. At this moment the health care professionals that are working in the field of diabetes and pregnancy are waiting for the results of the prospective multicentric study (HAPO study), hoping that a consensus could be reached about such a test.

Diabetes in pregnancy

A number of risk factors exist for pregnant women with diabetes and their babies. Collaborative care can ensure that women with pre-existing diabetes, and those who develop diabetes during pregnancy, receive appropriate and individualised care.

Diabetes complicating pregnancy

Despite the well-documented relationship between morbidity in pregnancy and pregestational maternal diabetes, the corrected perinatal outcome is, in most series, equal to or better than that of the general reference obstetric population. No single aspect or element of contemporary management is responsible for this improvement; rather, a combination of interventions seems responsible. Targeting delivery early in term, improved compliance, better glycemic control during pregnancy, improved control at conception, improved neonatal care, family planning, and early screening for fetal abnormalities all likely contribute to improved outcome. The currently observed rates of perinatal mortality suggest that an irreducible minimum mortality rate may be reached; however, large disparities in access to care and treatment continue to result in a wide range in rates of morbidity and mortality, a fact that pertains to outcomes in general as well as to pregnancies complicated by diabetes. The identification of women with lesser degrees of hyperglycemia as diabetic by lowering the thresholds for glucose tolerance test abnormality suggests an importance of the diagnosis that is not supported by evidence of either related morbidity or therapeutic benefit. The extrapolation of risk to women with lesser degrees of hyperglycemia seems to have little basis, and the management of women with mild glucose intolerance as if they had overt diabetes is unwarranted. The excess of resources dedicated to the identification and monitoring of an increasing number of women with mild abnormalities of glucose metabolism should prompt a reevaluation of these practices. Perinatal benefits of this expenditure are difficult to document or nonexistent, and there is a predictable increase in iatrogenic morbidities associated with the diagnosis. The exception in the most recent recommendations is the addition of a random glucose measure to screen for the rare women with overt undiagnosed diabetes who presents for prenatal care, because these women are at increased risk of morbidities related to diabetes. A curious statement was made in the summary and recommendations of the fourth International Congress on Gestational Diabetes: "There remains a compelling need to develop diagnostic criteria for GDM [gestational diabetes mellitus] that are based on the specific relationships between hyperglycemia and risk of adverse outcome." If these relationships are undefined, what is the import of the diagnosis? At the author's center, application of the new diagnostic thresholds for the diagnosis of gestational diabetes mellitus has increased the incidence to over 6%. Without a clear expectation of benefit, this increase represents an unsupportable investment of resources. What are the prospects for improving understanding of the relationships between glucose intolerance and pregnancy risks? The direction of new guidelines and recommendations seems to be moving away from resolution of the relationships. The new criteria result in the diagnosis of gestational diabetes in an increasing number of women who were previously normal. It is easier to differentiate women at an extreme of hyperglycemia from normal. Investigations will be even less able to identify attributable effects of glucose intolerance in pregnancy with the inclusion of women with lesser degrees of hyperglycemia. As evidenced in O'Sullivan's original series, women with fasting hyperglycemia in pregnancy are still presumed to be at increased risk of fetal death. This risk factor remains important in clinical management if insulin treatment, fetal surveillance, and early term delivery can reduce the risk of fetal loss. At the author's center, the relationships among outpatient measures of fasting glycemia, glucose tolerance testing results, and perinatal outcomes are evaluated. Preliminary results suggest that fasting glycemia measured at the time of a 50-g glucose tolerance test is significantly correlated with and as sensitive and predictive of morbidity as the glucose tolerance test diagnosis of gestational diabetes. If these results are confirmed, it will be difficult to rationalize continued glucose tolerance testing.

[Causes of premature labor in pregnancy complicated by diabetes depend on diabetes progression]

The aim of this study was to demonstrate what factors influence preterm termination of pregnancy complicated by diabetes, in dependence of diabetes progression. The following factors have been analysed: rate and causes of preterm labours according to White classification, mean duration of pregnancy, mode of delivery, birth weight, Apgar score and diabetes control in the preterm delivered women with different progression of disease. As a result we observed, that in G/A and G/B classes and in short lasting class B, the most common cause of preterm labour was spontaneous delivery and prematurity rate was low, oscillated between 1.7 and 15.8 percent. In those classes we also observed that diabetes control was very good or adequate. In D, R, F, and RF classes the most common cause of preterm labour is intrauterine fetal distress, that causes preterm termination of pregnancy, despite immaturity, and prematurity rate is 30-50 percent. We observed bad diabetes control in above mentioned classes.

Normal fetal pelvis: important factors for morphometric characterization with US

PURPOSE

To prospectively evaluate iliac angle and iliac length in a large number of normal fetuses and to identify factors that may influence these measurements.

MATERIALS AND METHODS

At antenatal ultrasonography (US) in 356 fetuses, the iliac angle and iliac length were measured at two axial levels (superior and inferior). In mixed linear models, the statistical significance and magnitude of effect on the measurement of iliac angle and iliac length were estimated for gestational age, fetal sex, maternal diabetes status, axial level, and spine position relative to the transducer.

RESULTS

Statistically significant effects were found for gestational age, axial level, and spine orientation but not for fetal sex or maternal diabetes status. The iliac angle was found to decrease by 15.7 degrees from the superior to inferior portion of the pelvis, decrease by approximately 0.37 degrees /wk, and decrease by as much as 15.6 degrees when the spine is directed to the side. Iliac length was found to increase by 0.8 mm/wk from 13 weeks to term, decrease by 1.2 mm from the superior to the inferior portion of the pelvis, and increase by as much as 1.29 mm when the spine is not directly subjacent to the transducer.

CONCLUSION

The axial level of measurement, gestational age, and spine orientation must be accounted for if these morphometric indexes are used to discriminate fetuses with and those without Down syndrome.

Diabetic embryopathy

The teratogenicity of human pregestational maternal diabetes mellitus (DM), classes B-T, is beyond any doubt and leads to a spectrum of malformations known as diabetic embryopathy (DE). Gestational DM (classes A1 and A2) is not an established teratogen yet. This is linked to its late diagnosis, usually only after the 20th week, and to the incomplete understanding of the pathogenesis of DE. Since class A-T DM affects approximately 5% of all pregnancies, intensive laboratory and clinical research continues to address the numerous aspects of DE. A review of this research during 1997 and 1998 is presented for the pediatrician in order to enhance the awareness of DE and its possible role in "idiopathic" malformations for children.

Reclassification after delivery of diabetes in pregnancy

Gestational diabetes mellitus (GDM) constitutes a risk factor for the development of non insulin-dependent diabetes mellitus (NIDDM). The search for parameters to provide discrimination between a high risk and a low risk for future development of NIDDM is today the aim of many investigations. The absence or presence of several factors such as glycemia during pregnancy and post partum, the need for insulin treatment, disorders of the pancreatic insulin secretion, the number of pregnancies, maternal obesity, the early diagnosis of GDM, the family history of diabetes mellitus, the race and immune disorders give rise to a very high relative risk (RR) of developing NIDDM. To know the degree of risk will allow a future appropriate clinical intervention to reduce the incidence of NIDDM and its economic cost.

[Diabetes mellitus: current classification based on cause and sharpened blood glucose limits for diagnosis]

Recently new definitions were agreed for the glucose tolerance test (GTT), for impaired glucose tolerance and for the classification of diabetes mellitus. The World Health Organization and the American Diabetes Association have been active on this point. The fasting glucose value has been lowered and been brought into line with the two hour value of the GTT. Fasting glucose values can now be used for the diagnosis of diabetes mellitus and of impaired glucose tolerance. The new classification is based on differences in cause of the diabetes. The classification includes diabetes mellitus types 1 and 2, pregnancy diabetes and 'other forms of diabetes'.

Coronary artery disease in insulin-dependent diabetes mellitus of pregnancy (class H): a review of the literature

Coronary heart disease and myocardial infarction are uncommon complications during pregnancy. Women with insulin-dependent diabetes mellitus (IDDM) have a much greater risk of serious coronary heart disease, but few cases of myocardial infarctions occurring during pregnancy have been reported. Significant maternal morbidity has been reported in half of these cases. This is a case of a myocardial infarction occurring at 21 weeks of gestation in a patient with class R/F IDDM and the subsequent pregnancy management as well as a review of the literature concerning Class H IDDM in pregnancy.

[Diabetic retinopathy during pregnancy]

Diabetic retinopathy is the leading of blindness between the age of 24-64 years and we know the half of this period corresponding to the peak fertility and childbearing years. The prevalence and severity of the retinopathy is strongly related to the duration of the disease and patient age. The progression of diabetic retinopathy during pregnancy can vary from minimal to market deterioration of the retina. So in diabetic women full retinal evaluation must be done as a part of prepregnancy counseling procedure. Patient who already have proliferative retinopathy during pregnancy are monitored frequently by ophthalmologist and lesser photocoagulation can be done safely during pregnancy.

Density distribution of erythrocytes in class A2 (insulin requiring) gestational diabetes

We evaluated the age distribution of erythrocytes in pregnancy complicated by gestational diabetes class A2 by the density distribution of cells (DDC) method. The values for normal pregnancy and nonpregnant women were obtained from recently published studies. The cumulative density distribution of cells (DDC) of women with gestational diabetes resembled that of normal pregnancy.

[Risk groups of newborn infants of diabetic mothers in relation to their somatic outcome and maternal diabetic metabolic status in pregnancy]

In a prospective study, neonatal morbidity of newborn children of diabetic mothers and its association with the maternal metabolism was determined. Particular attention was directed on the somatic outcome of the children and their frequent metabolic imbalances. In addition, we determined the influence of maternal biological and somatometrical variables on the somatic outcome of newborns. Dependent upon the mothers' and children' variables, risk groups of newborns (fetopathy groups) were defined to optimize clinical care and surveillance of newborns. A total of 810 children were included born to mothers with primary insulin dependent diabetes mellitus (IDDM), non insulin dependent diabetes (NIDDM), or gestational diabetes (GDM). Among the study population, 41.7% of children had macrosomia, 27.2% had a weight-length index > 1.2, 17.9% developed hypoglycemia and 19.5% hyperbilirubinemia within the initial 72 hours after birth. The somatic outcome of the children was significantly associated with pregnancy duration, maternal age, weight, height, and HbA1. Increasing maternal HbA1 prior to delivery (categorized in < 8.5%, 8.6-10%, > 10%) was associated with increased relative risk of incidence of neonatal morbidity. Finally, risk groups (fetopathy groups I-III) were defined according to maternal HbA1 value and somatic outcome of the newborns. The importance of these fetopathy groups for criteria of neonatal morbidity is demonstrated. Based upon categorization of newborn children into fetopathy groups, children should be allocated to specific concepts of appropriate surveillance and clinical care. The fetopathy classification may also serve as an independent tool for retrospective quality control of diabetic pregnancy.

Insulin infusion therapy in the intrapartum period

Glycemic control is important not only in the antepartum period but in the intrapartum period as well. Nursing management of the patient receiving insulin infusion therapy can assist in prevention of maternal and newborn morbidity. Careful glucose monitoring, insulin infusion therapy, and skilled nursing management of these complex patients result in the prevention of maternal and fetal injury and ensure a positive childbirth experience.

Prevention: the cost-effectiveness of the California Diabetes and Pregnancy Program

BACKGROUND

The California Diabetes and Pregnancy Program is a new preventive approach to improving pregnancy outcomes through intensive diabetes management preconception and early in pregnancy.

METHODS

Hospital charges and length of stay data were collected on 102 program enrollees and 218 control cases. Ninety program enrollees and 90 control cases were matched on mother's age. White's classification, and race. Regression models controlled for these variables in addition to MediCal status, birth weight, and enrollment in the program.

RESULTS

Hospital charges were about 30% less for program participants and days in the hospital were roughly 25% less. The program effects were larger for women that enrolled before 8 weeks gestation. More serious diabetics were also found to have larger reductions in charges and days.

CONCLUSION

After adjusting for inflation and differences in charges across hospitals, $5.19 is saved for every dollar spent on the program.

Significance of umbilical and uterine artery velocimetry in the well-controlled pregnant diabetic

The measurement of umbilical and uterine artery velocity waveforms was used to study pregnancies complicated by diabetes. Continuous wave Doppler velocimetry was used to identify the umbilical and uterine artery velocity waveforms. A systolic:end diastolic ratio (S:D ratio) was calculated to analyze the obtained velocity waveforms. We treated 33 tightly controlled and monitored diabetic gravidas. The mean blood sugar value for this population was 95 +/- 8 mg/dL, and the mean umbilical artery S:D ratio was 2.5 +/- 0.3. That group of patients was compared to a group on which we reported previously. Statistically significant differences were found between the well-controlled and poorly controlled populations in third-trimester S:D ratios, number of stillbirths and neonatal morbidity. Uterine artery velocimetry allowed the identification of a patient who developed preeclampsia. This study seems to have indicated that umbilical and uterine artery velocimetry may have an adjunctive role in the surveillance of pregnancies complicated by diabetes.

Pregnancy outcome in maturity onset diabetes at young age (MODY)

Diabetes mellitus is not a single disease, but rather a syndrome comprised of a variety of diseases characterized by hyperglycaemia. Indeed it has a heterogeneous nature. Maturity Onset Diabetes of the Young or MODY is an unusual, mild type of hyperglycaemia, which develops in young women, (below the age of 25), who do not require insulin. This study describes 10 pregnancies in MODY women, who are compared to a group of patients with insulin-dependent diabetes mellitus (IDDM), a group with gestational diabetes, and a control group of normal, healthy pregnant women. Our group of pregnant MODY patients proved to have an intermediate form of diabetes, more severe than gestational diabetes and yet not as severe as insulin-dependent diabetes mellitus. Mean duration of diabetes was shorter and mean daily insulin requirement (during pregnancy) was lower among MODY patients in comparison to IDDM gestants. Moreover the frequency of maternal complications and Caesarean deliveries in MODY patients were lower than in the IDDM group, but higher when compared to the gestational diabetes group.

Reassessment of White's classification and Pedersen's prognostically bad signs of diabetic pregnancies in insulin-dependent diabetic pregnancies

The classification systems developed over 20 years ago by White and Pedersen identified diabetic pregnancies at increased risk for perinatal mortality. To assess whether these same criteria would currently be valid, 199 diabetic pregnancies with deliveries from 1977 to 1983 were reviewed. Perinatal mortality rates for White's Classes B gestational (n = 72), B (n = 27), C (n = 67), and D + F + R (n = 33) were 2.9%, 11.1%, 14.9%, and 21.1%, respectively (p less than 0.05). White's classes were also predictive of pulmonary morbidity (12.5%, 18.5%, 22.4%, and 42.4%, respectively). The presence of one or more of the prognostically bad signs of pregnancy (n = 76) increased the perinatal mortality rate to 17.1% versus 7.3% among insulin-dependent diabetic pregnancies without prognostically bad signs (p less than 0.05). The presence of any prognostically bad signs of pregnancy was also predictive of pulmonary morbidity in general (31.6% versus 16.3%, respectively) and hyaline membrane disease in particular (13.2% versus 4.1%, respectively). Thus with use of modern obstetric management and medical care of the pregnant diabetic patient, both White's classification and Pedersen's prognostically bad signs of pregnancy continue to be predictive of perinatal mortality.

Gestational diabetes mellitus: a syndrome with phenotypic and genotypic heterogeneity

One hundred ninety-nine gravida with gestational diabetes mellitus (GDM) defined as "carbohydrate intolerance of varying severity with onset or first recognition during pregnancy" have been stratified into subgroups on the basis of fasting plasma glucose and evaluated for further phenotypic and genotypic heterogeneity. A significantly greater proportion of the women in all our groups were older and heavier than in a "control" population of 148 consecutive gravida with documented normal oral glucose tolerance. After correction for age and weight by covariate analysis, absolute insulinopenia in response to oral glucose could be demonstrated in all GDM groups, although exceptions were present in each. The incidence of diabetes in the mothers of our patients with GDM was 8-fold greater than in controls; the incidence in fathers did not deviate from control patterns. HLA-DR3 and DR4 antigens were more frequently present in GDM and the increase was statistically significant in blacks. At the time of diagnosis, cytoplasmic islet cell antibodies (ICA) were significantly more common in GDM associated with elevated fasting plasma glucose than in controls; the frequency of ICA was 18.4% (7/38) in women with fasting plasma glucose greater than or equal to 130 mg/dl. Our findings indicate that GDM entails genotypic as well as phenotypic diversity and may include patients with slowly-evolving Type I diabetes mellitus, as well as patients with Type II diabetes mellitus, and women with asymptomatic diabetes which antedated the pregnancy (i.e. pregestational diabetes mellitus). Appreciation of this heterogeneity should be incorporated into any evaluation of intervention strategies for women with GDM or into prognoses concerning their postpartum metabolic status.

Basis of the present classification of diabetes

The present classification of diabetes most widely used is that recommended by the National Diabetes Data Group and subsequently endorsed by the World Health Organization. This classification is primarily a clinical classification of diabetes because in most instances the etiology is unknown. The need for a standardized classification arose out of the recognition that diabetes was a syndrome rather than a single disease and the different terminologies which emerged. While certain types of diabetes can be classified according to specific etiology or associations with specific syndromes, the vast majority cannot. Insulin-dependent and noninsulin-dependent diabetes usually represent syndromes whose etiopathology is believed to differ and their clinical characteristics are usually distinctive. As evidence of etiological heterogeneity has increased there has been a tendency to adopt the terms Type I and Type II diabetes to indicate different etiologies, although the original usage of these terms was as a clinical classification to differentiate between insulin dependent and non-insulin-dependent disease. At present the use of the four terms to describe the common types of diabetes leads to confusion, which could readily be resolved by arriving at agreed definitions for each of these terms. While the NDDG-WHO classification has served to standardize terminology and stimulate research into the different causes of diabetes, some further refinement of the classification, together with some additional definition of terms, should be considered. The classification of diabetes most widely used at the present time is that suggested by the National Diabetes Data Group (NDDG) in the United States in 1979, which was subsequently recommended by the World Health Organization (WHO) Expert Committee on Diabetes Mellitus in 1980. It should be stressed that this classification was intended to be a uniform framework for clinical and epidemiological research, and that the classification would almost certainly have to be modified on the basis of new knowledge in the future.

Limitations and problems of diabetes classification from an epidemiological point of view

There are residual ambiguities between the two main current glycaemic definitions of the categories of DM, IGT and normal GT which should be resolved. IGT is clearly a highly heterogeneous category and could with advantage be resolved into its identifiable subsets though adequate data for this is not yet available. The concept of insulin dependency requires clearer definition for operational purposes. Biochemical parameters (e.g. C-peptide responses) may help. Attempts to combine clinical manifestations and pathogenic mechanisms in a single classification (e.g. IDDM/NIDD versus Type I/Type II) should be handled with care. If the term Type I is to be retained, it should be applied to a defined pathogenic process, not to a clinical type of DM. The term Type II is inadequately defined at present. IDDM and NIDDM, clinical descriptive terms, may be provoked by a variety of pathogenic mechanisms (i.e. they are 'heterogeneous'). They could be subclassified by mechanism (when known). More visibility should be given in classification to non-Europid forms of DM (e.g. 'Tropical or 'Nutritional' DM). A staging dimension should be recognised in classifications of DM. Future classifications will benefit from the incorporation of the presence or absence of susceptibility/resistance factors to diabetes itself or to its severe long term sequelae. There remain uncertainties about the definitions and clinical implications of gestational DM (and gestational IGT) not discussed above. It should be accepted that different user groups may need different subclassification of diabetes and glucose intolerance to meet their specific requirements and so long as this is made clear and definitions are adequate this should not be a problem. However, for the present, all groups should accept the proposed glycaemic definitions of DM or IGT for the purposes of comparability.

Alterations of maternal metabolism in normal and diabetic pregnancies: differences in insulin-dependent, non-insulin-dependent, and gestational diabetes

In normal and diabetic pregnancies, the placenta functions as a complex endocrine gland that modulates all classes of maternal nutrients to the fetus. The metabolic alterations of normal pregnancy are diabetogenic and associated with modest resistance to endogenous insulin. Pregnant women with carbohydrate intolerance represent three metabolically heterogeneous groups: type I (insulin-dependent), type II (non-insulin-dependent), and gestational diabetes. Patients with type I diabetes are at risk for ketosis and require replacement therapy because of a deficient production of insulin. They have decreased 24-hour, around-the-clock levels of C-peptide and glucagon, and lower nocturnal cortisol values and higher 24-hour prolactin levels than those of women with type II diabetes. Type II pregnant diabetic patients are not prone to ketosis and are more resistant to endogenous and exogenous insulin. They have higher fasting and meal-stimulated levels of C-peptide, accentuated fasting hypertriglyceridemia, and significantly lower high-density lipoprotein cholesterol levels than those of normal or type I women. In gestational diabetes, the metabolic stress of pregnancy evokes reversible hyperglycemia which may be associated with either a surfeit or a deficiency of insulin. These metabolic differences among diabetic pregnant women could have implications for placental structure and function that might influence fetal growth.

Optimal insulin delivery for the pregnant diabetic patient

It is now possible to virtually normalize ambient blood glucose levels in insulin-dependent diabetic women during pregnancy. Successful programs have been developed that utilize home blood glucose monitoring, physiologic delivery of insulin, and quantitation of caloric intake carefully matched to insulin dosage. The results of establishing normoglycemia throughout gestation appear to be a normalization of mortality and morbidity for both infant and mother. Pregnancy provides a need for continuous upward adjustment of insulin dose concomitant with the ongoing fetal and hormonal changes associated with gestation.