Background Pregnancy tends to reset the glucose homeostasis in the direction of diabetes. About 1–2% of all pregnant women develop an abnormal glucose tolerance in pregnancy, but most often glucose tolerance returns to normal postpartum. This condition is called gestational diabetes mellitus (GDM).

Aims Comparative study between gestational and pregestational diabetes in relation to glycemic control as regarding fetal and neonatal outcome.

Methods This study was conducted in Kasralainy Maternity hospital in Egypt from september 2011 to march 2012 and it included 60 pregnant women complicated by DM attending outpatient clinic or inpatient. Patients were classified into two groups, Gestational Diabetes: 30 pregnant women complicated by DM which is diagnosed for the first time during pregnancy and Pregestational Diabetes: 30 pregnant women who have DM that has been diagnosed prior to pregnancy.

The two groups were compared according to fetal (macrosomia and intrauterine fetal death) and neonatal (respiratory distress syndrome and birth injuries) complications. All patients were 18 to 40 years old, singltone pregnancy, with time of termination after completed 37 weeks.

Results Fetal macrosomia occurred more with GDM, on the otherhand birth injuries and RDS occurred more with Pre-GDM. Macrosomia and RDS were commoner among poor glycemic control in pregnant diabetic females than birth injuries and IUFD.

Conclusions Glycemic control started as early as possible (the best being preconceptional) is important to decrease the incidence of birth injuries, macrosomia, fetal mortality, the need for NICU admission (RDS).