TORONTO — Postpartum testing in women who had gestational diabetes during pregnancy should include both an oral glucose-tolerance test and a lipid profile, Genevieve Dubé and her colleagues advised in a poster presented at the joint annual meeting of the Canadian Diabetes Association and the Canadian Society of Endocrinology and Metabolism.
Data from a retrospective analysis of 223 women with gestational diabetes mellitus (GDM) during pregnancy revealed that postpartum glucose-tolerance abnormalities were common, affecting one-fourth of all women. Moreover, “isolated fasting glucose testing would have failed to identify most cases of postpartum dysglycemia,” noted Ms. Dubé, a dietician, and her colleagues at the Centre Régional du Diabète de Laval (Que.). The data also suggested that a lipid profile should be part of the assessment, because many of the women with previous GDM—including those with normal postpartum oral glucose-tolerance test (OGTT) results—have altered lipids suggestive of features of the cardiometabolic syndrome, they said.
The 223 women had received prenatal care between June 2004 and April 2005 at Laval's diabetic pregnancy clinic, where a program of routine postnatal GDM follow-up has been in place since 2002. The group had a mean age of 31 years and a mean body mass index of 28.3 kg/m
Of the 164 who underwent the OGTT, some form of impaired glucose tolerance was detected in 25% (41 patients), including frank type 2 diabetes in 4% (7 patients), isolated impaired glucose tolerance in 16% (26 patients), isolated impaired fasting glucose in 2% (3 patients), and both impaired glucose tolerance and impaired fasting glucose in 3% (5 patients).
Whatever fasting blood glucose (FBG) cutoff was used, more than half of dysglycemic women would have been missed if screening included only FBG. Among the 41 women with abnormal 2-hour OGTT results, just 49% had FBG values at or above 5.6 mmol/L, 41.5% had FBG levels of 5.8 mmol/L or higher, and 32% had FBG levels of 6.1 mmol/L or higher.
The need for insulin therapy and a first-trimester FBG above 6.1 mmol/L were the only risk factors that significantly predicted postpartum abnormal OGTT, with odds ratios of 1.89 and 3.41, respectively. Maternal age, BMI, parity, macrosomia, and nonwhite race were not predictive. Among the 165 women who underwent postpartum lipid tests, 70% had at least one abnormality, defined as a triglyceride level of 1.7 mmol/L or higher, HDL cholesterol level at or lower than 1.3 mmol/L, or a total cholesterol/HDL cholesterol ratio of 5.0 or greater. Cardiometabolic risk factors were not limited to those with abnormal OGTT results and diabetes. Two-thirds of the 123 women with normal postpartum glucose tolerance had at least one lipid abnormality; 23% had triglyceride levels of 1.7 mmol/L or higher, and 23% had HDL cholesterol of 1.3 mmol/L or lower. Only when those two abnormalities were combined was there a significant correlation with OGTT results.
Although it may be good to bring women in for postpartum testing while they're breast-feeding in order to avoid loss to follow-up, lactation can mask some lipid and glucose abnormalities, she noted.