Should all pregnant women be screened for gestational glucose intolerance?

Screening for gestational diabetes mellitus: a Caribbean perspective

Gestational diabetes mellitus (GDM) is defined as a glucose intolerance first recognised in pregnancy. The World Health Organization (WHO) in 2015 revised the definition into either diabetes in pregnancy (DIP) which includes pre-existing diabetes (type 1 or type 2) that antedates pregnancy or diabetes diagnosed during pregnancy with the WHO diagnostic criteria for diabetes mellitus (DM) in the non-pregnant state, and GDM for milder forms of hyperglycaemia in pregnancy. The main purpose of the screening and diagnosis of GDM is to identify pregnancies in which the foetus is at a high risk of an adverse perinatal outcome, and the mother and the offspring are of serious long-term sequelae. This review of the literature provides an overview of associated prevalence, risk factors and diagnosis of GDM. It also addresses the benefits of screening with supportive evidence. Based on this review, we recommend especially in low-resourced countries such as the Caribbean, adoption of a universal screening with the two-step method.

Establishing consensus in the diagnosis of gestational diabetes following HAPO: where do we stand?

New proposals for the diagnosis of gestational diabetes (GDM), promulgated by the International Association of Diabetes and Pregnancy Study Groups (IADPSG), will substantially increase the number of women diagnosed with GDM. This will have an enormous impact on healthcare resources, diverting attention away from genuinely high risk diabetic pregnancies. Randomized trials in 'mild' GDM indicate that the main effects of treatment are a 2 %-3 % reduction in birth weight, fewer 'big babies', and less shoulder dystocia. However, these studies used different diagnostic criteria, and women diagnosed by the broader IADPSG criteria may not derive the same modest benefit. Modeling indicates a very high cost per QALY, unless later development of type 2 diabetes can be prevented. Far from producing consensus, the IADPSG suggestion has thrown sharply into focus the need to assess critically the risks, costs and benefits of adopting criteria that may pathologize a large number of otherwise normal pregnancies.

Screening for gestational diabetes in the United Kingdom: a national survey

To determine the attitudes of British obstetricians to screening for gestational diabetes a postal questionnaire survey was undertaken. A questionnaire was sent to a single obstetrician in each of 255 obstetric hospitals identified in the United Kingdom. Of the 189 (75%) units that replied, only 42.3% had a protocol for screening for gestational diabetes. Routine antenatal screening was performed by urinalysis and blood glucose tests in 89.4% and 32.8% of units respectively. Clinical risk factors were used as an indication for routine blood glucose testing in 91.5% units. Following a positive screening test 54.5% of units performed a 75 g oral glucose tolerance test (GTT) and of these 64% relied on the World Health Organisation diagnostic criteria to interpret the result. There currently appears to be widespread variation in the practice of screening for gestational diabetes in the United Kingdom.

Women's experiences of being screened for gestational diabetes mellitus

OBJECTIVE

To assess if women screening positive for gestational diabetes mellitus (GDM) will experience a reduction in their quality of life.

DESIGN

Prospective survey

SETTING

Level III teaching hospital with a high-risk pregnancy service and neonatal intensive care unit.

POPULATION

Pregnant women prior to being screened for GDM, after screening and late in pregnancy

METHODS

Women were surveyed using the six-item short-form of the Spielberger State-Trait Anxiety Inventory, Edinburgh Postnatal Depression Scale and Short Form 36 Item Health Survey Further questions asked about the mother's perception of health and the concern the mother felt for the health of her unborn child, the adequacy of information given about the screening tests and its results, adequacy of information about the results of the diagnostic OGTT and women's overall experiences of being screened.

MAIN OUTCOME MEASURES

Anxiety, depression, health status, concerns about the health of the baby and perceived health.

RESULTS

After screening, women screening positive for GDM had lower health perceptions (p < 0.05), were less likely to rate their health as 'much better than one year ago' (p < 0.05) and were more likely to only rate their health as 'fair' rather than 'very good' or 'excellent' when compared with women screening negative (p < 0.01). No differences were found in levels of anxiety, depression or the concern women felt about the health of their baby

CONCLUSIONS

Screening for GDM had an adverse impact on women's perceptions of their own health.

Screening for gestational diabetes mellitus in a multiethnic population in New Zealand

We have compared the characteristics of those screened and unscreened for gestational diabetes mellitus (GDM) in a multiethnic population in New Zealand. All obstetric records for a 12-month period were reviewed manually and electronically. Pre-gestational diabetes status, screening for GDM and obstetric history were recorded. Data for 4885 singleton pregnancies, uncomplicated by known pre-existing diabetes were available. Overall 50.6% of women were screened for GDM using a glucose challenge test, ranging between 36.8% among Europeans to 68.5% among Pacific Islanders (P<0. 001). Attendance at a follow up oral glucose tolerance test among those with a positive screen was 77.4%, with no ethnic difference. Rates of GDM were 3.3, 7.9 and 8.1% for Europeans, Maori and Pacific Islanders. An estimated 45-72% of women with GDM went undetected. Although increasing weight was associated with an increased likelihood of screening, 44.9, 34.8 and 21.1% of obese (weight 85+kg) Europeans, Maori and Pacific Islanders, respectively, were not screened. Increasing age was not associated with increased screening. Screening for GDM is not occurring even in those with clear and agreed indications for selective screening. We hypothesise that the current debate over criteria for selective screening may be undermining screening for those most at risk.

Determinants of pregnancy outcome in patients with gestational diabetes

OBJECTIVES

To describe the experience of management of gestational diabetes 'GDM' among a high-risk population and to determine the relative contribution of maternal risk factors and some indices of glucose intolerance on pregnancy outcome.

METHODS

A total of 173 antenatal patients with GDM, matched to 337 non-diabetic controls were evaluated. Incidences of fetal macrosomia, large birth weight (> 4000 g), and operative delivery were noted. Patients with GDM were subgrouped into group I and II, according to the fasting blood glucose (FBG) level on the glucose tolerance test 'GTT', whether > or = or < 5.8 mmol/l, respectively. A logistic regression model was then developed with predictive variables, i.e. maternal weight, height, parity, gestational week at diagnosis of GDM, degree of glucose tolerance, treatment and means of fasting and post-prandial blood glucose measurements as independent variables against each of the outcome measures as dependent variables.

RESULTS

Compared with non-diabetics, patients with GDM were older in age, weight and parity. The mean fetal birth weight, incidences of macrosomia and babies > 4 kg were significantly higher among GDM patients. In patients with GDM the degree of glucose intolerance (determined by FBG on the GTT) and maternal weight were the only variables that significantly increased the risk of macrosomia and operative delivery. Within group I patients (FBG > or = 5.8 mg/dl) only 'maternal weight' significantly increased the risk of both having a baby > 4 kg, and operative delivery.

CONCLUSION

Among patients with gestational diabetes, a GTT with a FBG level > or = 5.8 mmol/l is a strong predictor for perinatal outcome. Maternal weight is an independent risk factor that increases the risk of both macrosomia and operative delivery.

Glucose metabolism assessment in pregnancy

OBJECTIVES

To review the literature regarding screening and definitive testing for Gestational Diabetes (GDM) and to assess whether treatment after identification changes perinatal/neonatal outcome.

DATA RESOURCES

Directed medline searches.

RESULTS

Gestational Diabetes Mellitus is defined as carbohydrate intolerance of variable severity with onset or first recognition during pregnancy. The fetal and neonatal risks resulting from GDM continue to be controversial. There is an increased risk of macrosomia, birth trauma, and neonatal hypoglycemia but other metabolic complications are uncommon. There is still continuing debate as to whether there is an increase in congenital anomaly or stillbirth rate. Maternal risks include increased operative intervention, infections and hydramnios. Screening and definitive testing for GDM is undertaken to identify those pregnancies at risk for macrosomia, birth trauma and neonatal hypoglycemia in the hope that treatment will reduce this risk. However, at the present time there is inadequate evidence as to whether intensive management aimed at euglycemia meaningfully changes perinatal/neonatal outcome.

CONCLUSION

In spite of conflicting evidence that treatment of GDM changes pregnancy outcome, screening and definitive testing for GDM should continue until large prospective trials confirm or refute the accepted standard of care.

An evaluation of fructosamine estimation in screening for gestational diabetes mellitus

Although persuasive arguments against routine screening for gestational diabetes mellitus (GDM) have been made, it is widely but not universally performed as a part of antenatal care. There is no international agreement on methods or criteria used for screening (or for diagnosis), and administered glucose-load methods have significant practical difficulties in a busy antenatal clinic setting. However, recent evidence supports the concept of an increased level of importance being given to a diagnosis of GDM, with interest in the fetal and neonatal origins of adult disease being added to the short-term obstetric and fetal concern during pregnancy. A second generation fructosamine test, corrected for total protein, has been evaluated as a practical alternative to glucose screening for GDM in a busy, multi-ethnic antenatal clinic. This achieved a 79.4% sensitivity and a 77.3% specificity for a diagnosis of GDM confirmed by a glucose tolerance test using Carpenter's modified criteria. In view of the organizational simplicity of this sample/test requirement, a wider evaluation is suggested together with a re-evaluation of clinical outcome criteria rather than blood glucose levels alone.

Screening for gestational diabetes in a multi-ethnic population

A multi-ethnic population was screened for gestational diabetes mellitus (GDM) using a venous plasma glucose estimation, 1 h following a standard 50 g glucose load. A significant difference in the ethnic distribution of screen-positivity was found. Amongst the screen-positive group the odds ratio (OR) for special care baby facility (SCBU) admission and birthweight > 3999 g were both increased (OR = 1.87 and 1.99). Only limited diagnostic testing by a glucose tolerance test (GTT) could be achieved for the screen-positive population. For patients with confirmed GDM (two or more abnormal values on a GTT) the OR for SCBU admission was further increased to 5.1, while the OR for increased birthweight was only 1.34. Clinical attention should be directed towards outcome assessment in order to properly evaluate the nature of and place for screening for GDM in multi-ethnic populations.

The 75 g oral glucose tolerance in pregnancy

A 75 g oral glucose tolerance test was performed between 26 and 32 weeks gestation in 1371 women attending an ante-natal clinic in Melbourne. Gestational diabetes according to various criteria was present in 4.2% (2 h plasma glucose > or = 8.0 mmol/l), 5.2% (2 h plasma glucose > or = 7.8 mmol/l) and 5.5% by the proposed Australian criteria (fasting plasma glucose > or = 5.5 mmol/l and/or 2 h plasma glucose > or = 8.0 mmol/l). The long-term implications of gestational diabetes in the development of diabetes and metabolic abnormalities for both the mother and her child in addition to related infant morbidity emphasise the urgent need for an agreed definition of this condition.

The genetics and pathophysiology of type II and gestational diabetes

The development of both type II diabetes and gestational diabetes is probably governed by a complex and variable interaction of genes and environment. Molecular genetics has so far failed to identify discrete gene mutations accounting for metabolic changes in NIDDM. Both beta cell dysfunction and insulin resistance are operative in the manifestation of these disorders. Specific and sensitive immunoradiometric assays found fasting hyperproinsulinemia and first-phase hypoinsulinemia early in the natural history of the disorder. A lack of specificity of early radioimmunoassays for insulin resulted in measuring not only insulin but also proinsulins, leading to overestimation of insulin and misleading conclusions about its role in diabetes. The major causes of insulin resistance are the genetic deficiency of glycogen synthase activation, compounded by additional defects due to metabolic disorders, receptor downregulation, and glucose transporter abnormalities, all contributing to the impairment in muscle glucose uptake. The liver is also resistant to insulin in NIDDM, reflected in persistent hepatic glucose production despite hyperglycemia. Insulin resistance is present in many nondiabetics, but in itself is insufficient to cause type II diabetes. Gestational diabetes is closely related to NIDDM, and the combination of insulin resistance and impaired insulin secretion is of importance in its pathogenesis.

The medical management of gestational diabetes in Australia within a solo private practice

This study reports the obstetric and fetal outcomes of 266 consecutive patients with gestational diabetes managed by a solo practitioner in private practice. Labour was spontaneous in 75.6% and 93.2% had a gestational age of delivery between 37 and 41 weeks. The elective Caesarean section rate of 14.7% was slightly higher than the rate for the overall obstetric population. Insulin therapy was required in 12.8% of the patients with a mean daily dose of 35.3 units. The rate of insulin use increased to 23.8% during 1993 when the criteria for its use was revised. This was associated with a significantly lower macrosomic rate of 3.6%. Overall there was a significant reduction in the number of babies weighing < or = 2500 g and no increase in the number of babies weighing > or = 4000 g. One patient only was admitted to hospital during this 30-month period and there was 1 neonatal death. These results indicate that successful medical management of gestational diabetes, with obstetric and fetal results similar to the overall obstetric population, is possible outside of tertiary institutions and specialized clinics.