Diabetes mellitus is not a single disease, but rather a syndrome comprised of a variety of diseases characterized by hyperglycaemia. Indeed it has a heterogeneous nature. Maturity Onset Diabetes of the Young or MODY is an unusual, mild type of hyperglycaemia, which develops in young women, (below the age of 25), who do not require insulin. This study describes 10 pregnancies in MODY women, who are compared to a group of patients with insulin-dependent diabetes mellitus (IDDM), a group with gestational diabetes, and a control group of normal, healthy pregnant women. Our group of pregnant MODY patients proved to have an intermediate form of diabetes, more severe than gestational diabetes and yet not as severe as insulin-dependent diabetes mellitus. Mean duration of diabetes was shorter and mean daily insulin requirement (during pregnancy) was lower among MODY patients in comparison to IDDM gestants. Moreover the frequency of maternal complications and Caesarean deliveries in MODY patients were lower than in the IDDM group, but higher when compared to the gestational diabetes group.