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

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.

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.

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.

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%.