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.