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%.