Gestational diabetes: problems in classification and implications for long-range prognosis

Pregnancy: An Underutilized Window of Opportunity to Improve Long-term Maternal and Infant Health-An Appeal for Continuous Family Care and Interdisciplinary Communication

Physiologic adaptations during pregnancy unmask a woman's predisposition to diseases. Complications are increasingly predicted by first-trimester algorithms, amplify a pre-existing maternal phenotype and accelerate risks for chronic diseases in the offspring up to adulthood (Barker hypothesis). Recent evidence suggests that vice versa, pregnancy diseases also indicate maternal and even grandparent's risks for chronic diseases (reverse Barker hypothesis). Pub-Med and Embase were reviewed for Mesh terms "fetal programming" and "pregnancy complications combined with maternal disease" until January 2017. Studies linking pregnancy complications to future cardiovascular, metabolic, and thrombotic risks for mother and offspring were reviewed. Women with a history of miscarriage, fetal growth restriction, preeclampsia, preterm delivery, obesity, excessive gestational weight gain, gestational diabetes, subfertility, and thrombophilia more frequently demonstrate with echocardiographic abnormalities, higher fasting insulin, deviating lipids or clotting factors and show defective endothelial function. Thrombophilia hints to thrombotic risks in later life. Pregnancy abnormalities correlate with future cardiovascular and metabolic complications and earlier mortality. Conversely, women with a normal pregnancy have lower rates of subsequent diseases than the general female population creating the term: "Pregnancy as a window for future health." Although the placenta works as a gatekeeper, many pregnancy complications may lead to sickness and earlier death in later life when the child becomes an adult. The epigenetic mechanisms and the mismatch between pre- and postnatal life have created the term "fetal origin of adult disease." Up to now, the impact of cardiovascular, metabolic, or thrombotic risk profiles has been investigated separately for mother and child. In this manuscript, we strive to illustrate the consequences for both, fetus and mother within a cohesive perspective and thus try to demonstrate the complex interrelationship of genetics and epigenetics for long-term health of societies and future generations. Maternal-fetal medicine specialists should have a key role in the prevention of non-communicable diseases by implementing a framework for patient consultation and interdisciplinary networks. Health-care providers and policy makers should increasingly invest in a stratified primary prevention and follow-up to reduce the increasing number of manifest cardiovascular and metabolic diseases and to prevent waste of health-care resources.

Classification of diabetes in pregnancy: time to reassess the alphabet

The White classification is a system of alphabetically designated categories of diabetes in pregnancy based on age at onset, duration of disease, and the presence or absence of vascular complications. The original classification system underwent several revisions, each progressively increasing in detail and complexity. Individual authors and institutions have modified the classes, resulting in identically lettered classes having different definitions. Some publications make reference to the class of diabetes by letter without providing a reference defining that class. Despite a 1994 American College of Obstetricians and Gynecologists Bulletin, which suggested that the White classification system was less helpful, publications still appear using lettered designations with and without modifications and with and without attendant definitions of terms. A clinically useful system of disease classification should consist of clearly defined, mutually exclusive, easily remembered categories. The current American Diabetes Association classification of diabetes fulfills these requirements and is applicable to diabetes during pregnancy. Adoption of such a system by the obstetrics community in verbal and written medical communication will likely enhance patient care and facilitate accurate data collection and comparison.

Prediction of persistent carbohydrate intolerance in patients with gestational diabetes

A 12-month prospective study was carried out in 120 Chinese patients with gestational diabetes who were found to have persistent carbohydrate intolerance at 6 weeks postpartum. The 75 g OGTT and WHO diagnostic criteria were employed for both antepartum and postpartum assessment. By 12 months, persistent carbohydrate intolerance was found in 13.3% of the patients only, 6 patients were diabetic while 10 had impaired glucose tolerance. Of those whose carbohydrate tolerance reverted to normal, 85% did so within the first 6 months. The clinical variables were analysed by multiple discriminant analysis using the logistic model. Five prognostic variables which were predictive of persistent carbohydrate intolerance at 12 months were identified. In order of decreasing predictive value, these included a high fasting glucose during pregnancy and at the first postnatal visit, a high antepartum 2 h blood glucose, the requirement of insulin during pregnancy, and a high postpartum 2 h blood glucose. Macrosomia, gestational age at diagnosis and a family history of diabetes were not predictive of persistent carbohydrate intolerance. Multiparity, maternal age and body mass index were of marginal significance only. The fitted logistic model provides a mechanism to estimate the probability of persistent carbohydrate intolerance. Such information will be helpful in patient counselling and in the efficient planning of postpartum medical follow-up.

Increased risk for gestational diabetes mellitus associated with insulin receptor and insulin-like growth factor II restriction fragment length polymorphisms

Gestational diabetes mellitus (GDM) is defined as glucose intolerance with onset or first recognition during pregnancy. We have examined restriction fragment length polymorphisms (RFLPs) near "candidate diabetogenic genes" as one approach to identify molecular markers for GDM genes. Genotypes for insulin hypervariable region (HVR), insulin-like growth factor II (IGF2), insulin receptor (INSR), and glucose transporter (GLUT1) RFLPs were studied in 96 GDM and 164 control subjects, matched to GDM for race, age, and gravidity. Logistic regression analysis was used to explore the relationship between genotypes at these candidate gene loci and GDM, while adjusting for the effects of potential confounding variables. Among black subjects, the INSR allele 1 (P = 0.001) and interactions between INSR allele 1 with body mass index (BMI) (P = 0.002) and history of DM in subject's mother (P = 0.004) contributed significantly to GDM risk. Among Caucasian subjects, a similar relationship between the INSR allele 1 (P = 0.007) and INSR allele 1-BMI interactions (P = 0.011) on GDM risk were observed. In Caucasians, an additional significant risk factor was determined by an INSR allele 1-IGF2 allele 2 interaction (P = 0.018). No risk factors were identified in Hispanic subjects. These data continue to support the hypothesis that GDM is a heterogeneous disorder with respect to phenotypic and genotypic features. Furthermore, our data suggest that risk for GDM in black and Caucasian subjects is not due to obesity perse but to interactions between obesity and INSR alleles. In Caucasian women, INSR and IGF2 alleles interact to confer additional risk for GDM. Thus genes underlying susceptibility to GDM in some women may be similar to genes conferring risk to NIDDM, while in others novel genes may contribute to GDM risk.

Does impaired glucose tolerance imply a risk in pregnancy?

Of 218 pregnant women with abnormal glucose tolerance by the criteria of the World Health Organization (1985) 81.2% had impaired glucose tolerance and 18.8% gestational diabetes. Gestational diabetic women were of higher parity, more obese, required insulin therapy more often, had more babies weighing greater than 4 kg and had higher fasting plasma glucose than women with impaired glucose tolerance. Women with gestational impaired glucose tolerance were older, of higher parity, more obese and had heavier babies than pregnant women with a normal screening plasma glucose. Compared with women with impaired glucose tolerance, gestational diabetic women were more likely to have abnormality, and more severe impairment of their glucose tolerance test in the puerperium.

Gestational diabetes--infant malformations and subsequent maternal glucose tolerance

The frequency of abnormal glucose tolerance in the first 12 months after gestational diabetes was found to be 33.3%, which is much higher than previously accepted. Women with gestational diabetes (Group 1 = 54 requiring insulin, Group 2 = 32 treated with diet alone) attending a metropolitan teaching hospital over a 3 1/2 year period were followed-up after delivery to determine their subsequent glucose tolerance. Of 86 seen 3 months after delivery, 2 had developed insulin-dependent diabetes mellitus (IDDM) and 2 noninsulin dependent diabetes mellitus (NIDDM), diagnosed by glucose tolerance testing. Another 38 returned for follow-up glucose tolerance testing at 12 months; of these 3 had impaired glucose tolerance (IGT), 7 had NIDDM, and one who had had NIDDM at 3 months now showed IGT after 9 months dietary treatment. Thus, 12 months after delivery, the cumulative prevalence of abnormal glucose tolerance was 14/42 (33.3%), 10 of the 42 being frankly diabetic (26%). Of the remaining 44 patients, 21 have not yet reached 12 months or were pregnant again, and 23 did not attend for glucose tolerance testing. Although the trend was for gestational diabetes mellitus (GDM) to recur earlier and more severely in subsequent pregnancies, in 3 instances the diabetes did not recur. Major congenital malformations occurred in 4 of the 86 babies (4.7%); minor malformations were found in a further 13 (15%) with no difference in frequency between Group 1 and Group 2.