Obstetrical Outcome following Diagnosis of Gestational Diabetes in the Third Trimester (>29 Weeks) versus Second Trimester (24–28 Weeks): A Retrospective Comparative Study

This study aimed to compare obstetrical outcomes between women diagnosed with gestational diabetes mellitus (GDM) in the third trimester after testing negative for GDM in two-step screening in the second trimester and women diagnosed in the second trimester. This retrospective study compared obstetrical outcomes between 375 women diagnosed with GDM in the second trimester and 125 diagnosed in the third trimester. Among women diagnosed with GDM in the third versus second trimester, the incidences were higher of morbid obesity (body mass index ≥35 kg/m2), macrosomia, and cesarean section (CS) due to suspected macrosomia: 23.2 versus 9.8%, p < 0.001; 44.0 versus 10.1%, p < 0.001; and 24.8 versus 6.3%, p < 0.001, respectively. For those diagnosed in the third versus second trimester, the incidences were lower of hypertensive disorders of pregnancy and intrauterine growth restriction, and a lower proportion of women needed pharmacological therapy for glucose control: 2.4 versus 9.0%, p = 0.016; 0.8 versus 8.2%, p < 0.001; and 12.0 versus 29.7%, p < 0.001, respectively. Multivariate analysis supported a correlation between third-trimester-diagnosed GDM and macrosomia, and between second-trimester-diagnosed GDM and hypertensive disorders of pregnancy. Among women diagnosed with GDM in the third compared with the second trimester, the incidence of morbid obesity was higher; accordingly, the risks were higher for large for gestational age infants and delivery by CS, and lower for hypertensive disorders. Guidelines regarding repeat oral glucose tolerance testing in the third trimester should be considered following prospective studies.· Third-trimester GDM was 29.9% among women with normal second-trimester screening.. · Morbid obesity and macrosomia were more frequent in third- versus second-trimester GDM.. · Incidence of preeclampsia was lower in third- versus second-trimester-diagnosed GDM..