Hyperglycemia and Adverse Pregnancy Outcome HAPO Study

A primary aim of the HAPO Trial was to establish uniform GDM screening criteria based on maternal and fetal outcomes (38). A total of 25,505 pregnant women at 15 centers in 9 countries underwent 2-h 75-g OGTTs between 24 and 32 weeks of gestation. Primary outcomes included mac-rosomia, Cesarean delivery and neonatal hypoglycemia. Secondary outcomes included delivery before 37 weeks, shoulder dystocia or other birth injury, hyperbilirubinemia and preeclampsia. While the risk of adverse pregnancy outcomes uniformly increased with greater glucose levels, no threshold existed, making the decision regarding cutoffs difficult. The risk of macrosomia increased approximately fivefold as fasting glucose increased above 75 mg/dl, 1-h glucose increased above 105 mg/dl, or 2-h glucose increased above 90 mg/dl. In other words, a fasting glucose greater than or equal to 100 mg/dl was associated with a risk of macrosomia five times that of a fasting glucose less than 75 mg/dl, with absolute macrosomia rates of 25% vs. 5%. Correlation with other outcomes was less marked, although still significant. HAPO excluded women with severe hyperglycemia from the analysis (fasting glucose greater than 105 mg/dl or 2-h glucose greater than 200 mg/dl), so the association actually underestimated the strength of the correlation by excluding women with extremely elevated glucose. An initial recommendation for screening cutoffs incorporating the HAPO results is expected later in 2009.

Following the publication of the consensus opinion, it is likely that medical organizations may eliminate the two-step procedure, as HAPO did not perform an initial screen. Whether the diagnostic test will include the measurement of fasting glucose only or the performance of a 75-g OGTT with measurements of fasting glucose and measurement of plasma glucose 1 h and 2 h after the 75-g oral glucose load still awaits determination as well. As HAPO focused on women with only mild hyperglycemia, women with preexisting diabetes would presumably be detected by these definitions as well.

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