Almost 9% of pregnant women develop gestational diabetes. Recently, new diagnostic criteria have become available. Both insulin and oral antidiabetic agents are available for therapy. At the DIP symposium (The7th international Symposium on Diabetes, Hypertension, Metabolic Syndrome and Pregnancy) in Florence, it was reported how diabetes in pregnant women should be diagnosed and treated in a timely manner.
Diabetes is an increasing problem in pregnant women. Whereas in 1980 only 5% of pregnant women developed gestational diabetes or had diabetes before, by 2008 this figure had risen to almost 9% [1]. Nearly half of pregnant women with gestational diabetes also develop a manifest form of diabetes in the subsequent 20-30 years [2].
Gestational diabetes is defined as “any degree of glucose intolerance occurring or first diagnosed during pregnancy” [3–6]. While some researchers consider the current criteria to be too stringent, they are a result of criticism that there is too little evidence to determine the risk to mother and child associated with glucose intolerance [7].
Recommendations of the IADPSG for the diagnosis of gestational diabetes
Based on the HAPO study, a large, blinded multicenter study of the course of pregnancy in hyperglycemia [8], the International Association of Diabetes and Pregnancy Study Group (IADPSG) issued new recommendations for the diagnosis and classification of hyperglycemia in pregnancy in 2010 [9]. “The diagnostic strategy involves two distinct steps,” summarized Prof. David McIntyre, MD, director of the Mater Medical Research Institute at the University of Queensland in Brisbane, Australia. As a first step, the Working Group for the Detection of Diabetes in Pregnant Women recommends screening all pregnant women in general and paying special attention to populations with high type 2 diabetes prevalence. At the first doctor’s visit after pregnancy is established, fasting blood glucose, HbA1c, or casual blood glucose should be measured as a first step. If the results indicate manifest diabetes (Tab. 1), it is treated according to guidelines.
However, if the results do not allow a manifest diagnosis of diabetes, even though fasting blood glucose is between 5.1 and 6.9 mmol/l, gestational diabetes exists. The second step in diabetes screening, he said, is for all pregnant women who have not previously been diagnosed with manifest diabetes or gestational diabetes but who have a fasting blood glucose of less than 5.1 mmol/l to undergo an oral glucose tolerance test (OGTT) with 75 mg glucose between the 24th and 28th weeks of pregnancy (Table 2).
The IADPSG defined cutoffs for the diagnosis of gestational or manifest diabetes (Table 1). Prof. McIntyre added that if these IADPSG guidelines were followed consistently, gestational diabetes could be detected more than twice as often [10].
Diabetes societies in countries such as America, Germany, Italy, Japan and India have now adopted the IADPSG criteria. “However, the recommendations have also been criticized by some experts,” Prof. McIntyre reported. Suboptimal is, for example, the high cost of the many tests and the partial unreliability of the OGTT. Obesity in pregnant women is also an understudied topic, he said. According to Prof. McIntyre, the data indicate a benefit of screening. The long-term consequences and effects of the therapy on mother and child remained to be investigated.
First two weeks diet, then medication
Detecting and treating gestational diabetes can significantly reduce mortality and morbidity in babies, according to Prof. Mark Landon, MD, Chair of the Department of Obstetrics and Gynecology at Ohio State University College of Medicine, USA.
According to the fifth International Workshop on Diabetes Care, fasting blood glucose should be less than 5.3 mmol/l, after one at <7.8 mmol/l, and after two hours after OGTT at <6.7 mmol/l [11]. Medications are not immediately necessary for gestational diabetes, Prof. Landon suggested. Patients should first be advised to try diet for at least two weeks. However, pregnant women with a fasting glucose value of >5.3 mmol/l could be prescribed insulin after only one week of diet or right at the time of diagnosis [12].
Suitable insulins for treatment are: Lispro, Aspart, Glargine and Detemir. Prof. Landon summarized the studies, (comparison with human insulin): Women on lispro had similar HbA1c levels after six weeks as those on regular human insulin. However, fewer hypoglycemias occurred with lispro [13], lispro appears to lower postprandial glucose levels more effectively [14]. The insulin preparation Aspart was also able to lower postprandial blood glucose better than human insulin. No difference was seen in perinatal outcomes with lispro and aspart compared with human insulin [15]. “Rapid-acting analog insulins are better suited than human insulin to reduce postprandial hyperglycemia,” Prof. Landon summarized. “These two preparations should be the standard insulin at mealtimes.”
The long-acting insulins glargine and detemir have been little studied in pregnant women, Prof. Landon reported. Studies indicate that nocturnal hypoglycemia occurs less frequently. However, a possible mitogenic activity of glargine and detemir had not been clarified. “Studies have yet to show whether these insulins are better than human insulin,” Prof. Landon said.
Oral medications have the advantage of being easy to take, which can increase compliance. Of the sulfonylureas, only glyburide has been shown to have minimal transfer to the fetus. In clinical trials, neonatal hypoglycemia did not occur more frequently [16]. Glyburide can be used to lower blood glucose similarly to human insulin. Further, symptomatic hypoglycemia in pregnant women occurred less frequently with glyburide. 4% of women treated with glyburide still required insulin because glyburide could not be detected in cord blood and the neonatal outcomes of glyburide and insulin are comparable [17].
Metformin can lower blood sugar as well as insulin and appears to be similarly safe. However, the use of insulin appears to be more common, but nearly 50% of women treated with metformin require supplemental insulin [18]. Prof. Landon noted that there are still too few studies comparing maternal and infant outcomes between insulin and oral antidiabetic agents.
A systematic review found no differences between the incidence of congenital malformations with insulin compared with glyburide or with metformin; birth weight was also comparable [19]. “Both insulin and glyburide or metformin can be used during pregnancy,” Prof. Landon said. The short-term risks, if any, of oral antidiabetic agents are minimal compared with insulin, he said. However, further studies are needed to ensure long-term safety for mother and child, according to Prof. Landon.
Literature list at the publisher
Felicitas Witte, MD
Source: The7th international Symposium on Diabetes, Hypertension, Metabolic Syndrome and Pregnancy, Florence, March 14-16, 2013.
HAUSARZT PRAXIS 2013; 8(6): 43-44
