The relationship between abnormal glucose tolerance and hypertensive disorders of pregnancy in healthy nulliparous women

OBJECTIVE: The study's aim was to determine whether healthy nulliparous women with abnormal glucose tolerance during pregnancy are at increased risk for development of pregnancy-associated hypertension or preeclampsia. STUDY DESIGN: A series of 4589 healthy nulliparous women from 5 university centers were evaluated prospectively to determine whether calcium supplementation would prevent preeclampsia. Pregnancy-associated hypertension was a diastolic blood pressure greater than or equal to 90 mm Hg on 2 occasions 4 hours to 1 week apart. Pregnancy-associated proteinuria was proteinuria greater than or equal to 1+ by dipstick testing on 2 occasions 4 hours to 1 week apart, proteinuria;greater than or equal to 300 mg/24 h, a protein to creatinine ratio of greater than or equal to 0.35, or a single dipstick measurement of greater than or equal to 2+. Preeclampsia was defined as pregnancy-associated hypertension and pregnancy-associated proteinuria documented within 7 days of each other. Normal glucose tolerance was a plasma glucose level <140 mg/dL 1 hour after a 50-g oral glucose challenge. Abnormal glucose tolerance was a plasma glucose level greater than or equal to 140 mg/dL 1 hour after a 50-g oral glucose challenge followed by a 9-hour 100-g oral glucose tolerance test yielding <2 abnormal values. Gestational diabetes mellitus was a plasma glucose level greater than or equal to 200 mg/dL 1 hour after a 50-g oral glucose challenge in the absence of an oral glucose tolerance test or greater than or equal to 2 abnormal plasma glucose values in a 3-hour 100-g oral glucose tolerance test (greater than or equal to 105 mg/dL fasting, greater than or equal to 190 mg/dL at 1 hour, greater than or equal to 165 mg/dL at 2 hours, or greater than or equal to 145 mg/dL at 3 hours). For purposes of this study women with preeclampsia were excluded from the category of pregnancy-associated hypertension. RESULTS: Calcium supplementation did not prevent pregnancy-associated hypertension or preeclampsia. Of 3689 women with complete glucose testing data, 227 (6%) had abnormal glucose tolerance and 81 (2%) had gestational diabetes mellitus. Compared with women with normal glucose tolerance, women with abnormal glucose tolerance were significantly older, had greater body mass index,and were more likely to be white non-Hispanic, to smoke, and to have private medical insurance. Among women with gestational diabetes mellitus, after adjustment for clinical center the relative risks of preeclampsia and of all hypertensive disorders were increased (relative risk 1.67, 95% confidence interval 0.92-3.05, and relative risk 1.54, 95% confidence interval 1.28-2.11, respectively). Risk ratios were not substantially reduced after further adjustment for race and body mass index (odds ratios 1.41 and 1.48, respectively). Even within the normal range, multivariate analysis demonstrated that the level of plasma glucose 1 hour after a 50-g oral glucose challenge was an important predictor of preeclampsia. CONCLUSION: Even within the normal range, the level of plasma glucose 1 hour after a 50-g oral glucose challenge was positively correlated with the likelihood of preeclampsia. Women with gestational diabetes mellitus were at increased risk for hypertensive disorders during pregnancy after adjustment for clinical center, race, and body mass index, although the increase was not statistically significant. These findings suggest that insulin resistance may play a role in the pathogenesis of the hypertensive disorders of pregnancy.