Diabetes mellitus is critical to address in preconception counselling because it significantly affects both maternal and fetal outcomes. Poor glycemic control before and during early pregnancy increases the risk of congenital malformations, miscarriage, and preeclampsia. Optimizing blood glucose levels preconceptionally reduces these risks, improves placental function, and promotes healthy fetal development. Effective management includes ensuring tight glycemic control, medication review, and patient education. This proactive approach is essential to minimize complications and improve pregnancy outcomes.

Reference: Williams Obstetrics, Cunningham FG, 26th Edition.