Jane Hirst and colleagues determined the prevalence and outcome of gestational diabetes mellitus in urban Vietnam and found that choice of criteria greatly affected prevalence, and has implications for the ability of the health system to cope with the number of cases.
Gestational diabetes mellitus (GDM) is increasing and is a risk for type 2 diabetes. Evidence supporting screening comes mostly from high-income countries. We aimed to determine prevalence and outcomes in urban Viet Nam. We compared the proposed International Association of the Diabetes and Pregnancy Study Groups (IADPSG) criterion, requiring one positive value on the 75-g glucose tolerance test, to the 2010 American Diabetes Association (ADA) criterion, requiring two positive values.
Methods and Findings
We conducted a prospective cohort study in Ho Chi Minh City, Viet Nam. Study participants were 2,772 women undergoing routine prenatal care who underwent a 75-g glucose tolerance test and interview around 28 (range 24–32) wk. GDM diagnosed by the ADA criterion was treated by local protocol. Women with GDM by the IADPSG criterion but not the ADA criterion were termed “borderline” and received standard care. 2,702 women (97.5% of cohort) were followed until discharge after delivery. GDM was diagnosed in 164 participants (6.1%) by the ADA criterion, 550 (20.3%) by the IADPSG criterion. Mean body mass index was 20.45 kg/m2 in women with out GDM, 21.10 in women with borderline GDM, and 21.81 in women with GDM, p<0.001. Women with GDM and borderline GDM were more likely to deliver preterm, with adjusted odds ratios (aORs) of 1.49 (95% CI 1.16–1.91) and 1.52 (1.03–2.24), respectively. They were more likely to have clinical neonatal hypoglycaemia, aORs of 4.94 (3.41–7.14) and 3.34 (1.41–7.89), respectively. For large for gestational age, the aORs were 1.16 (0.93–1.45) and 1.31 (0.96–1.79), respectively. There was no significant difference in large for gestational age, death, severe birth trauma, or maternal morbidity between the groups. Women with GDM underwent more labour inductions, aOR 1.51 (1.08–2.11).
Choice of criterion greatly affects GDM prevalence in Viet Nam. Women with GDM by the IADPSG criterion were at risk of preterm delivery and neonatal hypoglycaemia, although this criterion resulted in 20% of pregnant women being positive for GDM. The ability to cope with such a large number of cases and prevent associated adverse outcomes needs to be demonstrated before recommending widespread screening.
Please see later in the article for the Editors' Summary.
Gestational diabetes mellitus (GDM) is diabetes that is first diagnosed during pregnancy. Like other types of diabetes, it is characterized by high levels of sugar (glucose) in the blood. Blood-sugar levels are usually controlled by insulin, which is made by the pancreas. Hormonal changes during pregnancy and the baby's growth demands increase a pregnant woman's insulin needs, and if her pancreas cannot make enough insulin, GDM develops, usually in mid-pregnancy. Risk factors for GDM include a high body mass index (a measure of body fat), excessive weight gain or lack of physical activity during pregnancy, and glucose intolerance (an indicator of diabetes that is measured using the “oral glucose tolerance test”). GDM increases the risk of premature delivery, induced delivery, and having a large-for-gestational-age baby (gestation is the time during which the baby develops within the mother). It also increases the baby's risk of having low blood sugar (neonatal hypoglycemia). GDM, which can often be controlled by exercise and diet, usually disappears after pregnancy but increases the risk of diabetes developing later in both mother and baby.
Why Was This Study Done?
The prevalence (occurrence) of diabetes is increasing rapidly, particularly in low/middleincome countries as they become more affluent. Because GDM increases the subsequent risk of diabetes, some experts believe that screening for GDM should be included in prenatal care as part of diabetes preventative strategies. However, most of the evidence supporting GDM screening comes from high-income countries, so in this prospective cohort study (a study that analyses associations between the baseline characteristics of a group of patients and outcomes), the researchers investigate the prevalence of GDM (diagnosed using the oral glucose tolerance test) and the consequences of GDM among women attending an urban hospital in Viet Nam, a low/middle-income country. An oral glucose tolerance test measures a patient's blood-sugar level after an overnight fast, and one and two hours after consuming a sugary drink. The International Association of the Diabetes and Pregnancy Study Groups (IADPSG) and the American Diabetes Association (ADA) guidelines state, respectively, that one and two of these blood-sugar measurements must be abnormally high for a diagnosis of GDM. In this study, the researchers use both guidelines to diagnose GDM.
What Did the Researchers Do and Find?
Nearly 3,000 women who attended the hospital for routine prenatal care had a glucose tolerance test at around 28 weeks' gestation and were followed until discharge after delivery. Women who had GDM diagnosed by the ADA criterion were referred for dietary advice and glucose monitoring. Those diagnosed by the IADPSG criterion only were described as having “borderline” GDM and received standard prenatal care. GDM was diagnosed in 6.1% and 20.3% of the women using the ADA and IADPSG criteria, respectively. After allowing for other factors that might have affected outcomes, compared to women without GDM, women with GDM or borderline GDM were more likely to deliver prematurely, and their babies were more likely to have neonatal hypoglycemia. Also, women with GDM (but not borderline GDM) were more likely to have their labor induced than women without GDM.
What Do These Findings Mean?
These findings show that the criterion used to diagnose GDM markedly affected the prevalence of GDM among pregnant women attending this Vietnamese hospital—the use of the IADPSG criterion more than tripled the prevalence of GDM and meant that a fifth of the study participants were diagnosed as having GDM. Importantly, the findings also show that GDM diagnosed using the IADPSG criterion was associated with an increased risk of preterm delivery and neonatal hypoglycemia. Although these findings may not be generalizable to other settings within Viet Nam or to other countries, they highlight the need to demonstrate that sufficient resources are available to cope with an increased GDM burden before recommending widespread screening using the IADPSG criterion. Moreover, because the long-term significance of GDM diagnosed using the IADPSG criterion is not known, all the potential benefits and harms and the costs of screening and treating GDM in low-income settings need to be further investigated before any recommendation for “universal” GDM screening is made.
Please access these websites via the online version of this summary at http://dx.doi.org/10. 1371/journal.pmed.1001272.
The US National Institute of Diabetes and Digestive and Kidney Diseases provides information for patients on diabetes and on gestational diabetes (in English and Spanish)
The UK National Health Service Choices website also provides information for patients about diabetes and about gestational diabetes, including links to other useful resources
The American Diabetes Association also provides detailed information for patients and professionals about all aspects of diabetes, including gestational diabetes (in English and Spanish)
The International Association of the Diabetes and Pregnancy Study Groups (IADPSG) 2010 recommendations on the diagnosis and classification of gestational diabetes are available
The charity Diabetes UK provides detailed information for patients and carers, including information on gestational diabetes; its blog includes a personal story about gestational diabetes, and its website includes a selection of other stories from people with diabetes; the charity Healthtalkonline also has an interview describing a personal experience of gestational diabetes
MedlinePlus provides links to additional resources on diabetes and on gestational diabetes (in English and Spanish)