Clinical features of overt versus diagnosed pre-existing diabetes in pregnancy.

Overt diabetes in pregnancy (ODP) was originally included in gestational diabetes mellitus, which was positioned between normal glucose tolerance and pre-existing diabetes mellitus (PDM) in perinatal risk. This retrospective study aimed to clarify the differences between women with ODP and those with PDM. Compared with women with PDM (n =  162), those with ODP (n = 76) had higher HbA1c levels especially in the first trimester (8.2 ± 1.5% vs 7.2 ± 1.5%; P < 0.001). Furthermore, women with ODP had higher pre-pregnancy body mass index (30.8 ± 7.0 vs 28.5 ± 5.6 kg/m2; P = 0.010), and a higher incidence of congenital anomalies (19.7% vs 9.3%; P = 0.035). In conclusion, ODP was not milder than PDM; women with ODP did not only have poorer glycemic control but also had poorer pre-pregnant weight control. Their burdens could be relieved through appropriate management before pregnancy.