Objective: Our purpose was to determine whether gestational diabetics with risk factors for gestational diabetes have worse glucose tolerance and poorer birth outcomes than those without risk factors.
Study design: We conducted a nonconcurrent cohort study of gestational diabetics identified by universal screening and delivered from Jan. 1, 1990, to Dec. 31, 1992. Multiple gestations and patients with chronic medical conditions were excluded. The following risk factors for gestational diabetes mellitus were abstracted: obesity (> 80 kg), family history of diabetes, previous gestational diabetes mellitus, and previous macrosomic, stillborn, or anomalous fetus. Patients with one or more risk factors were compared with those without risk factors. A group of low-risk nondiabetic patients served as controls. The incidences of A2 diabetes mellitus, cesarean section, neonatal macrosomia, and shoulder dystocia were the outcome variables of interest.
Results: Selective screening would have failed to detect 43% of gestational diabetics. Twenty-eight percent of the missed gestational diabetics would have required insulin (class A2). When compared with controls, patients with gestational diabetes mellitus were at increased risk for macrosomia (26% vs 11%, p < 0.01), cesarean section (37% vs 15%, p < 0.01), and shoulder dystocia (9% vs 2%, p < 0.05). Patients with and without risk factors did not differ in mean maternal age, gestational age at delivery, birth weight, incidence of requiring insulin, macrosomia, or cesarean delivery. The similarities between those with and without risk factors remained after stratification by maternal age (> or = 30 years).
Conclusion: Gestational diabetics are at increased risk for adverse birth outcomes compared with low-risk controls. Class A2 diabetes mellitus and fetal macrosomia with its attendant risks are equally prevalent among patients with and without risk factors for gestational diabetes mellitus. Because > 40% of cases will be missed with selective screening, universal screening should be favored for detection of gestational diabetes mellitus.