Correlation between first- and early third-trimester glucose screening test results

One hundred twenty-four normal gravidas had paired first- and early third-trimester (26-32 weeks) 1-hour oral glucose screening tests performed. First-trimester oral glucose screening test values correlated significantly with third-trimester glucose screening test results for the entire population, for whites and non-whites, and for normal-weight and obese patients. First-trimester oral glucose screening test values at or below 110 mg/dL were seldom associated with third-trimester oral glucose screening test results at or above 135 mg/dL and were not associated with abnormal 3-hour glucose tolerance test (GTT) results. Nine of the gravidas (7.3%) were diagnosed with gestational diabetes mellitus during the third trimester, all of whom had first-trimester glucose screening test results above 110 mg/dL. The difference in incidence of gestational diabetes mellitus between gravidas having first-trimester glucose screening test results at or below 110 mg/dL (0%) and those having values above 110 mg/dL (16.4%) was highly significant (P less than .0001). For patients with first-trimester glucose screening test values at or below 110 mg/dL, third-trimester glucose screening may be unnecessary. In contrast, for gravidas having first-trimester glucose screening test results at or above 135 mg/dL, there is a high positive predictive value for elevated repeat glucose screening test results during the early third trimester. Patients having elevated first-trimester glucose screening values at or above 140 mg/dL are at particularly high risk for elevated glucose screening test results later in pregnancy and should forego repeat 1-hour third-trimester glucose screening in favor of a direct third-trimester 3-hour GTT.     

Could the fasting plasma glucose assay be used to screen for gestational diabetes?

The fasting plasma glucose assay was compared with the one-hour post-glucose test as a screening test for identification of gestational diabetes. Of 4,561 consecutive patients screened with a 50-g glucose test, 968 (21.2%) had results > or = 135 mg/dL; 141 (14.6%, or 3.1% of the total) were found to have diabetes. In the 968 patients, the area under the fasting plasma glucose receiver operating characteristic curve was greater than that under the glucose screening test curve, indicating greater discriminatory value of the former test. Of the 116 patients who had sequential glucose screening tests and fasting plasma glucose assays performed twice during pregnancy, a significant correlation was found for fasting plasma glucose values, but not for glucose screening test values. We conclude that the fasting plasma glucose assay may perform better than the one-hour post-glucose test as a screening test for gestational diabetes. Based on these data, a population-based prospective study seems justified.     

Correlation between one-hour, 50-g glucose screening values in successive pregnancies

OBJECTIVE: To investigate the relationship between one-hour, 50-g oral glucose screening test results in successive pregnancies and to assess the risk of gestational diabetes in women who had a previously negative glucose screening test during a prior pregnancy. STUDY DESIGN: Sixty-nine women were studied who had successive pregnancies delivered at intervals ranging from one to four years. All had glucose screening tests performed at 24-32 weeks of gestation during both pregnancies. The relationship between glucose screening test results was examined for interpregnancy intervals of up to two, three and four years. RESULTS: The correlation for interpregnancy glucose screening test results was .60, .49 and .47 for pregnancy intervals of up to two, three and four years, respectively (P < .001). The mean glucose screening test result was 108 +/- 23 mg/dL for prior pregnancies and 104 +/- 21 mg/dL for subsequent pregnancies (no significant difference). A screening test result > or = 140 mg/dL occurred in 1.6% of cases in which a previous test result was < 140 mg/dL during a prior pregnancy. CONCLUSION: A glucose screening test result of < 140 mg/dL during pregnancy is strongly predictive of a subsequent negative screening test result in a succeeding pregnancy when it occurs within four years. Under such circumstances, the risk of gestational diabetes during a subsequent pregnancy is reduced by 85-95% to no more than 0.3%.     

Gestational diabetes. Is a 50-g screening result > or = 200 mg/dL diagnostic?

OBJECTIVE: To evaluate the diagnosis of gestational diabetes based on a 50-g, one-hour glucose screening test result > or = 200 mg/dL. STUDY DESIGN: Retrospective ascertainment of pregnant women who had a 50-g, one-hour glucose screening test result > or = 200 mg/dL was performed among prenatal care registrants. The diagnosis of gestational diabetes was determined by 100-g, three-hour oral glucose tolerance test (GTT) results and/or repeated fasting serum glucose measures. RESULTS: In 1995, 69 women were referred to the gestational diabetes clinic with a 50-g result > or = 200 mg/dL. Four women could not be classified, two had pregestational glucose intolerance and four charts were unavailable. Of the remaining 59 women, 11 (19%) had normal three-hour GTTs, and 48 (81%) were diagnosed with gestational diabetes (35 [59%], A1; 13 [22%], A2). There was one large-for-gestational-age (LGA) infant born in the nondiabetic group (9%), 13 LGA infants born in the A1 group (37%) and 6 LGA infants born to the A2 diabetics (46%). The relationship between maternal diagnosis and LGA outcome was statistically significant. CONCLUSION: A 50-g screening test result > or = 200 mg/dL is not diagnostic of gestational diabetes. Nearly one of five such women had a normal three-hour oral GTT. Overdiagnosis of gestational diabetes may lead to unnecessary pregnancy surveillance and intervention.     

Screening for gestational diabetes in Sicily.

OBJECTIVE: To establish the prevalence of gestational diabetes in a universally screened population living in Messina, Sicily, as the first step in evaluating the cost: benefit ratio of screening for carbohydrate intolerance in pregnancy. STUDY DESIGN: Between October 1989 and March 1995, 1,000 pregnant women underwent screening for gestational diabetes with a 50-g, one-hour glucose challenge test. All the risk factors were registered. RESULTS: Two hundred sixty subjects had a value of > or = 135 mg/dL and underwent a full three-hour oral glucose tolerance test. Of them, 46 (4.6%) met the Carpenter-Coustan diagnostic criteria for gestational diabetes. CONCLUSION: The apparent incidence of gestational diabetes (1.2%) prior to screening was only 25% of the incidence determined with the protocol of universal screening (4.6%). If we assume that timely diagnosis and treatment of gestational diabetes provides an important opportunity to improve obstetric outcome and reduce perinatal morbidity, and since women with gestational diabetes are at increased risk of developing diabetes later, the knowledge that the true prevalence is almost four times that previously reported is a determinant of a future evaluation of the cost:benefit ratio of screening universally for gestational diabetes.     

Effect of advancing pregnancy on the glucose tolerance test and on the 50-g oral glucose load screening test for gestational diabetes

To determine the validity of the 50-g, one-hour glucose screening test for gestational diabetes in relation to the duration of pregnancy, 101 patients from a high-risk population had the screening test in the first trimester and glucose tolerance tests (GTT) in the second and third trimesters. The sensitivity (88%) and specificity (82%) of the screening test were similar to values reported when the test is performed later in pregnancy. However, immediate follow-up GTTs in the second trimester revealed only 25% instead of 88% of the gestational diabetic patients uncovered by the positive screening tests. Guidelines for screening for gestational diabetes should include follow-up with a third-trimester GTT on all patients who have positive screening tests even in the presence of normal follow-up second trimester GTTs.     

Cost-effective criteria for glucose screening

To study cost-effective screening criteria for gestational diabetes, a prospective study of 1012 patients was completed. All patients underwent a glucose screen between 26 and 30 weeks of gestation, consisting of a 50-g oral glucose load followed by a one-hour plasma glucose determination. Patients with a glucose screen greater than or equal to 130 mg/dL were studied with a standard three-hour oral glucose tolerance test. The incidence of gestational diabetes was 2.4% (24 of 1012). Only one gestational diabetic was identified with a glucose screen below 150 mg/dL. Twenty-two of the 24 cases were at least 24 years old. Twenty-one of the 24 (88%) gestational diabetes had a glucose screen greater than or equal to 150 mg/dL and were 24 years old or greater. The cost of the diagnosis in these latter patients was 40% of the cost of diagnosis of universal screening with a threshold of 130 mg/dL. It is concluded that screening with a threshold of 150 mg/dL only patients who are at least 24 years old should be considered an alternative to universal screening.     

Abnormal glucose screening tests in pregnancy: a risk factor for fetal macrosomia

Of 2276 patients who underwent screening for gestational diabetes mellitus, 1854 (81.5%) had normal glucose screening tests after a 50-g carbohydrate load (serum glucose below 135 mg/dL). Three hundred fifty-seven patients (15.7%) had abnormal glucose screening tests and went on to complete three-hour glucose tolerance tests, of whom 176 (48.7%) were shown to be nondiabetic when further tested using a carbohydrate-loaded, 100-g glucose, three-hour glucose tolerance test. The 176 women with abnormal glucose screens but normal glucose tolerance tests were compared with the 1854 who had normal screening values. The frequency of infants weighing more than 4000 g (greater than 95th percentile at our institution) was 11.9% in the study group and 6.4% in the control group (P = .0086). When the data were corrected for other macrosomia risk factors (advanced age, high parity, obesity, white race, and prolonged gestation), there was still a significantly higher frequency of macrosomia in the study group; this fact suggests that patients with minor abnormalities of carbohydrate metabolism during pregnancy are at risk for delivering a macrosomic infant.     

Screening for gestational diabetes mellitus in adolescent Hispanic Americans

OBJECTIVE: To determine the incidence of gestational diabetes mellitus (GDM) in an adolescent Hispanic American population. STUDY DESIGN: A retrospective review of 326 women < 20 years of age who identified themselves as Hispanic American was conducted and the incidence of gestational diabetes determined. RESULTS: Thirty adolescent Hispanic Americans (9.2%) had an abnormal result (> or = 140 mg/dL) after 50-g, one-hour oral glucose challenge testing. These women underwent three-hour oral glucose tolerance tests, and five met the criteria for GDM. The incidence of GDM in this population was 1.5% (5/326) (95% confidence interval, 0.6, 3.7). CONCLUSION: The incidence of GDM in adolescent Hispanic Americans is so low that universal screening may not be warranted.     

Gestational diabetes screening in subsequent pregnancies of previously healthy patients

OBJECTIVE: Our purpose was to evaluate women without gestational diabetes mellitus in an index pregnancy for the likelihood that gestational diabetes would develop and for risk factors for carbohydrate intolerance in a subsequent pregnancy.Study Design: A retrospective review of medical records at a teaching hospital universally screening for gestational diabetes identified multiparous women who had been delivered twice between 1994 and 1997 and who, in the first (index) pregnancy, had had a normal result on a screening test with 50 g of glucose used in a "glucola" beverage (< or =140 mg/dL). RESULTS: In this population with normal glucose screening values in the index pregnancy, 352 (92.4%) of 381 women had at least one risk factor for gestational diabetes. However, none of the 381 women had gestational diabetes in the subsequent pregnancy (0/381, 95% confidence interval < or =1%), including 45 (12. 4%) who had an abnormal result on the 50-g glucose screening test. Regression analysis showed this test result in the index pregnancy (P =.001) to be the only studied variable significantly associated with the 50-g glucose value in the subsequent pregnancy. CONCLUSION: Despite a high rate of risk factors for gestational diabetes, women in our population with a normal glucose value in an index pregnancy have a minimal risk (<1%) that gestational diabetes will develop in a subsequent singleton pregnancy within 4 years. This factor may be included in determining whether women should undergo screening for gestational diabetes.     

Elevated plasma homocysteine levels in gestational diabetes mellitus

OBJECTIVE: This prospective study investigated the occurrence of hyperhomocysteinemia in a population of patients with gestational diabetes. The aim was to determine whether elevated plasma homocysteine is associated with gestational diabetes in Turkish women. STUDY DESIGN: This prospective controlled study was conducted in the Department of Obstetrics and Gynecology of the Baskent University Faculty of Medicine between April 2002 and June 2003, and involved 304 Turkish women with uncomplicated pregnancies who were at 24-28 weeks gestation. The women in the study were assigned to one of three groups according to the results of the 50-g glucose screening and the oral glucose tolerance test (OGTT): group 1 comprised women who had normal glucose levels (< or = 135 mg/dL) after the 50-g challenge; group 2 comprised women with abnormal screening test results (> 135 mg/dL) but normal OGTT results; and group 3 comprised patients with gestational diabetes mellitus (GDM) according to the OGTT. Levels of fasting glucose, homocysteine, vitamin B(12) and folic acid, total cholesterol, high density lipoprotein (HDL) cholesterol, and triglycerides, low density lipoprotein (LDL) cholesterol and very low density lipoprotein (VLDL) cholesterol levels were measured in the three groups. Levels of insulin sensitivity were calculated using the homeostasis model assessment (HOMA) formula. RESULTS: The mean level of homocysteine in group 1 was significantly lower than the levels in groups 2 and 3 (p < 0.001) The mean triglyceride and VLDL levels in group 3 were significantly higher than the corresponding levels in group 1 (p < 0.05 for both). There were no significant differences among the groups with respect to levels of total cholesterol, vitamin B(12), folic acid, creatinine, fasting glucose or insulin. The mean HOMA value in group 3 was significantly higher than that in group 1 (p < 0.05). Only the blood glucose level after the 50-g glucose screening [p = 0.000, 95% confidence interval (CI) 0.009-0.027] had a significant correlation with homocysteine levels. CONCLUSION: In this prospective study of Turkish women, we found that patients with gestational diabetes and women with abnormal screening test results (> 135 mg/dL) but normal OGTT results have higher homocysteine levels than normal pregnant women. This increased level seems to be related to an abnormal 50-g test but not to insulin resistance. Further investigations are needed to follow up for these patients in the postpartum period and later in their life.     

Gestational diabetes mellitus and lesser degrees of pregnancy hyperglycemia: association with increased risk of spontaneous preterm birth

OBJECTIVE: To investigate whether different degrees of maternal glucose intolerance are associated with the risk of spontaneous preterm birth. METHODS: We performed a cohort study of 46,230 pregnancies screened by a 50-g, 1-hour oral glucose tolerance test between 24 and 28 gestation weeks at the Northern California Kaiser Permanente Medical Care Program. Spontaneous preterm birth was defined as an infant born at less than 37 gestation weeks with at least one of the following: spontaneous labor, preterm premature rupture of membranes, or incompetent cervix. Glucose tolerance status was categorized as normal screening (1-hour plasma glucose less than 140 mg/dL), abnormal screening (1-hour plasma glucose of at least 140 mg/dL with a normal diagnostic 100-g, 3-hour oral glucose tolerance test result), Carpenter-Coustan (plasma glucose measurements during the diagnostic oral glucose tolerance test met the thresholds but were lower than the National Diabetes Data Group thresholds), and gestational diabetes mellitus (GDM) by the National Diabetes Data Group criteria. RESULTS: One thousand nine hundred fifty-six spontaneous preterm births occurred. Age-adjusted incidences of spontaneous preterm birth were 4.0% in normal screening, 5.0% in abnormal screening, 6.7% in Carpenter-Coustan, and 6.7% in GDM. In a logistic regression model adjusted for age, race-ethnicity, preeclampsia-eclampsia-pregnancy-induced hypertension, chronic hypertension, polyhydramnios, and birth weight for gestational age, pregnancies with abnormal screening, Carpenter-Coustan, and GDM had a significantly higher risk of spontaneous preterm birth than pregnancies with normal screening (relative risk [95% confidence interval]: 1.23 [1.08, 1.41], 1.53 [1.16, 2.03], and 1.42 [1.15-1.77], respectively). CONCLUSION: The risk of spontaneous preterm birth increased with increasing levels of pregnancy glycemia. This association was independent of perinatal complications that could have triggered early delivery.     

Clinical predictors for a high risk for the development of diabetes mellitus in the early puerperium in women with recent gestational diabetes mellitus

OBJECTIVE: The purpose of this study was to identify which maternal, antepartum, or neonatal clinical parameters were predictive for a high risk of diabetes mellitus in the puerperium in women with recent gestational diabetes mellitus and to calculate the associated diabetes mellitus rates and odds ratios. STUDY DESIGN: One thousand six hundred thirty-six women underwent an oral glucose tolerance test within 1 to 4 months of delivery. Demographic, historic, and antenatal glycemic parameters and neonatal outcome parameters were tested by univariate and multivariate logistic regression for risk of postpartum diabetes mellitus. Continuous variables were divided into quartiles that compared the upper to lower quartile adjusted odds ratio and prevalence of diabetes mellitus. RESULTS: Postpartum diabetes mellitus was diagnosed in 230 women (14.1%) according to the American Diabetes Association criteria (1997). No maternal demographic or neonatal parameters were significantly associated with diabetes mellitus. The final model of independent predictors in decreasing significance included the highest fasting plasma glucose level during pregnancy, any fasting plasma glucose level of > or = 105 mg/dL (class A(2)), the area under the curve of pregnancy oral glucose tolerance test, gestational age at diagnosis, previous gestational diabetes mellitus history, and 50-g glucose challenge test results. The fasting plasma glucose level was the best discriminator, with a 21-fold (95% CI, 4.6-96.3) increased odds ratio comparing the 4th quartile (fasting plasma glucose level, >121 mg/dL; diabetes mellitus rate, 36.7%) to 1st quartile (fasting plasma glucose level, < 95 mg/dL; diabetes mellitus rate, 0.5%). The presence of previous gestational diabetes mellitus or current class A(2) gestational diabetes mellitus approximately doubled the odds ratio for diabetes mellitus. The odds ratio increased 3- to 4-fold when the area under the curve was > or = 33.36 min small middle dot g/dL (4th quartile) or the glucose challenge test was > or = 155 mg/dL (2nd-4th quartiles) and decreased > 50% if gestational diabetes mellitus was diagnosed at > 27 weeks (3rd-4th quartile). CONCLUSION: During pregnancy, the highest fasting glucose level, followed by the severity of glucose intolerance, and earlier gestational diabetes mellitus diagnosis were the best predictors for postpartum diabetes mellitus. Diabetic education should begin during pregnancy, especially for women who are identified to be at a high risk when they are highly motivated and under medical care.     

Can glucose tolerance test predict fetal hyperinsulinism?

Objective To establish cut off levels for oral glucose tolerance test in pregnancy using fetal hyperinsulinism as a clinical endpoint.
Design Capillary blood glucose levels at 0, 1, and 2 hours after the ingestion of either 1 g/kg or 75 g glucose, at 28 (SD 5) weeks of gestation were analysed in 220 women with elevated amniotic fluid insulin levels [≥ 42 pmol/L (≥ 7 μU/mL)] after a mean (SD) of 31 weeks (3) and in 220 nondiabetic controls.
Results In women with elevated amniotic fluid insulin levels the mean (SD) capillary blood glucose values at 0, 1, and 2 hours were 5.2 mmol/L (1.0) [94 mg/dL (18)], 10.5 mmol/L (1.4) [189 mg/dL (25)] and 8.2 mmol/L (2.0) [147 mg/dL (36)], respectively. The one-hour value had the highest sensitivity to predict elevated amniotic fluid insulin levels. The 5th centile of the one-hour blood glucose levels representing a detection rate of 95% was 8.9 mmol/L (160 mg/dL).
Conclusion Glucose cut off levels in most established oral glucose tolerance test criteria are too high, to accurately predict amniotic fluid hyperinsulinism. A one-hour test may be sufficient for detecting amniotic fluid hyperinsulinism. Since different loads (1 g/kg, 75 g or 100 g) and blood fractions (venous plasma or capillary blood) have minimal impact on oral glucose tolerance test results, a single one-hour cut off of 8.9 mmol/L (160 mg/dL), independent of the sampling method, may be appropriate for the diagnosis of gestational diabetes mellitus severe enough to cause amniotic fluid hyperinsulinism.     

Serial changes in the 50-g oral glucose test in pregnancy: implications for screening

To quantitate the effect of advancing pregnancy on the screening test for gestational diabetes, 550 patients were given a 50-g oral glucose screening test at 20, 28, and 34 weeks' gestation. A significant increase in the plasma glucose value was found, with a mean increase of 1.1 +/- 1.9 mg/dL per week from 20-34 weeks' gestation (r = 0.39, P less than .01). Only 34 patients (6.2%) had a positive screening test at 20 weeks' gestation, and it appears that routine screening in a low-risk population at 20 weeks is not warranted. Sixty patients (10.9%) with a negative screening test at 20 weeks had a positive test at 28 weeks. Forty-four patients (8.0%) with a negative test at 28 weeks had a subsequent positive test at 34 weeks. The overall incidence of gestational diabetes in this population was 4.9%. Currently, screening is recommended at 24-28 weeks for all pregnancies that have not been previously identified as having glucose intolerance. Eleven percent of the gestational diabetics in our population would have been undetected had we screened only at 24-28 weeks. This quantitative information may be helpful in deciding whether rescreening later in pregnancy is indicated.     

Gestational diabetes: fasting and postprandial glucose as first prenatal screening tests in a high-risk population

OBJECTIVE: To evaluate the value of fasting (FPG) and 2-hour postprandial (PPG) plasma glucose as screening tests for gestational diabetes mellitus (GDM) in a high-risk population during early pregnancy. STUDY DESIGN: At their first prenatal visit, 708 women underwent FPG and PPG for universal screening for GDM, with the diagnosis confirmed by the 75-g oral glucose tolerance test (World Health Organization criteria). The area under the receiver operating characteristic curve (AUC) was used to analyze the performance of the 2 screening tests. RESULTS: Of 184 (25.9%) women with GDM, 79 (42.9%) were identified before 18 weeks. The AUC for FPG to predict GDM was 0.579 (95% CI 0.531-0.627). Though a threshold of 85 mg/dL achieved minimally acceptable sensitivity, 79.9%, the corresponding specificity remained poor, 27.5%, with a false positive rate (FPR) of 72.5%. The AUC for PPG was 0.717 (95% CI 0.670-0.765); a cutoff of 95 mg/dL achieved a sensitivity of 79.9% and FPR of 53.1%. CONCLUSION: Though GDM could be diagnosed in > 40% women in early pregnancy at their first prenatal visit, the poor specificity and high FPR of FPG and PPG, alone or in combination, make them unsuitable screening tests for GDM.     

Glucose screening in Mexican-American women

OBJECTIVE: We sought to describe the predictive value for gestational diabetes mellitus (GDM) using different glucose challenge test thresholds in Mexican-American women. METHODS: A prospective population-based study of 6,857 gravid women, who were tested with a 50-g glucose challenge test at 24-28 weeks of gestation, was performed. A screening value of 130 mg/dL or greater was followed by a 3-hour, 100-g oral glucose tolerance test. Gestational diabetes mellitus was diagnosed by 2 or more abnormal values using the Carpenter and Coustan criteria. For purpose of analysis, GDM diagnosis was categorized with glucose challenge test values in 10-mg/dL increments. A comparison between Carpenter-Coustan and the National Diabetic Data Group criteria for GDM diagnosis was performed for each glucose challenge test threshold category. Sensitivity and specificity for GDM diagnosis were further calculated for different glucose challenge test thresholds (130, 135, and 140 mg/dL). RESULTS: Overall, GDM was diagnosed in 469 of 6,857 (6.8%) women, and one abnormal oral glucose tolerance test value was tested in 351 of 6,857 women (5.1%). Normal glucose challenge test results (threshold less than 130 mg/dL) were obtained in 4,316 of 6,857 women. An elevated glucose challenge test value increases the risk of GDM, but even in high glucose challenge test thresholds (more than 180 mg/dL), the predictive value for GDM was only 50%. The sensitivity and specificity for GDM diagnosis using 3 different glucose challenge test thresholds were as follows: threshold 130 mg/dL or more: 97% and 63%; threshold 135 mg/dL or more: 91% and 73%; and threshold 140 mg/dL or more: 85% and 78%, respectively. CONCLUSION: Data suggests that an elevated glucose challenge test level cannot be used as a single diagnostic tool for GDM even in high test thresholds. A threshold of 130 mg/dL may be recommended as a screening threshold for GDM in Mexican-American women. LEVEL OF EVIDENCE: II-3     

Are patients with positive screening but negative diagnostic test for gestational diabetes under risk for adverse pregnancy outcome?

OBJECTIVE: Our aim was to determine the obstetrics outcomes of patients with positive 1-h glucose challenge test (GCT), but negative diagnostic test for gestational diabetes. METHODS: Pregnancy records of 409 pregnants were reviewed. Patients were screened for gestational diabetes mellitus (GDM) with one-hour 50 g glucose challenge test (GCT) at 24-28 weeks of gestation. Patients with glucose challenge tests values > or = 130 mg/dL were refered for the 3 h, 100-g oral glucose tolerance test (OGTT). Positive GCT but negative for OGTT group (Group A) were compared retrospectively with the group of negative GCT (Group B) for obstetrics outcomes. RESULT: GDM and impared glucose tolerance (IGT) were diagnosed in 33 (7.6%) and 46 (10.5%) patients, respectively. We identified 141 (34.4%) patients with positive GCT but negative for OGTT (Group A) and 189 (46.2%) patients with negative GCT (Group B). Gestational weight gain, polyhydramnios, family history of diabetes mellitus were significantly higher in group A than group B (P < 0.05). Prevalance of preterm labor, hypertension, cesarean delivery, mean birthweight, proportion of babies admitted to neonatal intensive care unit were similar in both groups. CONCLUSION: There are some differences for pregnancy outcomes between pregnants with positive GCT but negative for OGTT and negative GCT. These patients should be followed up carefully during the antepartum and intrapartum period.     

The twentieth century: The century of progress and medicine

The standard criteria for the diagnosis of gestational diabetes (GDM) is based on two abnormal values of a 3-h-100-g oral glucose tolerance test (GTT). Although a markedly elevated 1 h–50-g screen value has been suggested to support a diagnosis of GDM, limited data are available to substantiate this empiric observation. Our purpose was to examine the utility of various 50-g screen cutoff values in establishing the diagnosis of gestational diabetes.

We identified 422 gravidas with a positive 50-g screen (≥135 mg/dl) who underwent additional glucose testing. GDM was defined according to the National Diabetes Data Group (NDDG) standards for the 3-h GTT. An analysis employing the criteria of Carpenter and Coustan was performed for comparison. If a patient had an elevated 50-g value and no 3-h GTT was performed, a fasting serum glucose ≥140 mg/dl was considered evidence of gestational diabetes.

One hundred twenty four (29.4%) had GDM as defined by the NDDG criteria; this increased to 161 (38%) when the diagnosis was based on Carpenter and Coustan's criteria. The mean (≥SD) gestational age at screening was 24 ± 7 weeks. As expected, the prevalence of GDM increased in relation to an increasing 50-g value. All subjects with a 50-g screen < 216 mg/dl had evidence of gestational diabetes and required insulin for glycemic control.

Patients with a 50-g screen ≥220 mg/dl do not all require a 3-h GTT. Those with a fasting serum glucose of ≥140 mg/dl may begin diet therapy, glucose monitoring, and insulin as indicated. If the fasting serum glucose is < 140 mg/dl, a 3-h GTT should be performed for confirmation of GDM. This approach will facilitate rapid therapeutic intervention and reduce the cost of care in this subset of patients. Gravidas with a very high 50-g screen are at significant risk of requiring insulin to maintain euglycemia during pregnancy.     

Use of oral glucose tolerance test in early pregnancy to predict late-onset gestational diabetes mellitus in high-risk women

AIM: To evaluate if any single plasma glucose level from the four values of the normal 100-g oral glucose tolerance test (OGTT) in early pregnancy (< or =20 weeks of gestation) could predict gestational diabetes mellitus (GDM) diagnosed from a second OGTT in late pregnancy (28-32 weeks). METHODS: Glucose levels of pregnant women at high-risk for GDM, who had had a normal early OGTT, and who underwent the second test in late pregnancy, were studied. Each of the four plasma glucose values of the early OGTT was determined for sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV). The receiver operating characteristic curves of these four OGTT values were then constructed to find the optimal value to predict late-onset GDM. RESULTS: Of 193 pregnant women who had had a normal early OGTT, 154 also had a normal OGTT in late pregnancy while 39 had an abnormal test and were diagnosed with GDM. Among the four glucose values of the early OGTT, the 1-h value yielded the best diagnostic performance to predict late-onset GDM. The sensitivity, specificity, PPV, NPV, and area under the curve achieved from its optimal cutoff level of > or =155 mg/dL (8.6 mmol/L) were 89.7%, 64.3%, 38.9%, 96.1%, and 0.77, respectively. CONCLUSIONS: A 1-h glucose value > or =155 mg/dL at the early OGTT yielded the best diagnostic performance. However, the low specificity and PPV rendered it suboptimal to predict late-onset GDM. Nevertheless, a considerable number of high-risk women could avoid the second OGTT in late pregnancy due to its high sensitivity and NPV.