The Implications of a "Flat" Oral Glucose Tolerance Test Curve in Pregnancy.

Objective:  This study aimed to determine whether pregnant women who have "flat" oral glucose tolerance test (OGTT) curves in pregnancy are at increased risk of maternal or neonatal adverse outcomes.

Study design:  We conducted a retrospective cohort study of the perinatal outcomes of pregnant women whose 100-g OGTT curve was "flat," defined by a fasting serum glucose level below 95 mg/dL and the remaining values below 100 mg/dL. We compared their perinatal outcomes to women whose OGTT curve was "normal." The primary outcomes compared were the prevalence of macrosomic and small for gestational age (SGA) neonates. Secondary outcomes included hypertensive disorders of pregnancy (HDP), prelabor anemia, thrombocytopenia, intrauterine fetal demise, placental abruption, indicated induction of labor, meconium-stained amniotic fluid, mode of delivery, postpartum hemorrhage, blood product transfusion, postpartum readmission, neonatal gender, gestational age at delivery, preterm birth, birth weight, low birth weight, umbilical artery pH < 7.1, Apgar score <7 at 5 minutes, neonatal intensive care unit admission, neonatal respiratory and infectious morbidity, and hypoglycemia. Composite adverse maternal and neonatal outcomes were also evaluated.

Results:  There were 1,060 patients in the study group and 10,591 patients in the control group. Patients with a flat OGTT were younger (28.3 vs. 29.8, p < 0.001) and less likely to be over 35 years old (14.1 vs. 23.4%, p < 0.001). They had a reduced risk of delivering a macrosomic neonate (11.4 vs. 15.1%, OR = 0.7 [0.58-0.89], p = 0.001) and having an unplanned cesarean delivery (7.5 vs. 10.2%, OR = 0.8 [0.58-0.96], p = 0.002). There was no difference in the rate of composite adverse maternal (14.0 vs. 15.4%, OR = 0.9 [0.7-1.0], p = 0.1) or neonatal outcome (5.3 vs. 4.5%, OR = 1.2 [0.9-1.5], p = 0.15). Neonates had a slightly lower mean birth weight (3,474 vs. 3,505 g, p = 0.04) but the rate of SGA was similar in the two groups (2.5 vs. 1.8%, OR = 1.3 [0.9-2.0], p = 0.08).

Conclusion:  Pregnant women whose OGTT curve is flat have a lower risk of delivering macrosomic neonates and undergoing unplanned cesarean delivery and are not at increased risk of adverse maternal or neonatal outcomes. More research is required to evaluate the relationship between different OGTT curves and the fetal growth rate.

Key points: · Patients with a "flat" OGTT have a reduced risk of macrosomia.. · Patients with a "flat" OGTT have a reduced risk of cesarean delivery.. · Patients with a "flat" OGTT are not at increased risk of growth restriction..