Despite significant improvements in the treatment of diabetes mellitus, both pregestational (PGDM) and gestational diabetes (GDM) represent a danger to the embryo, foetus, and pregnancy. Congenital abnormalities, particularly those of the heart, neurological system, musculoskeletal system, and limbs, may be more common in people with PGDM. PGDM can cause macrosomia in the foetus, but it can also restrict foetal development in the face of severe maternal problems, such as nephropathy. Stillbirth and perinatal mortality, cardiomyopathy, respiratory illness, and perinatal asphyxia are among possible perinatal consequences of PGDM. GDM, which usually appears in the second part of pregnancy, causes comparable but less serious issues. Their severity increases with earlier development of GDM and is inversely proportional to glycemic control. Early GDM commencement may result in an increase in the risk of congenital abnormalities. Both PGDM and GDM can lead to a variety of motor and behavioural neuro developmental issues, such as an increased risk of attention deficit hyperactivity disorder (ADHD) and autism spectrum disorder (ASD). With better diabetes management, the incidence and severity of most complications decreases. Hyperglycemia in the mother and foetus, increased oxidative stress, epigenetic alterations, and other, less well-defined pathogenic processes are all linked to diabetic-induced harm in pregnancy.