Abstract Aim: Both pre-gestational (PGDM) and gestational diabetes mellitus (GDM) make pregnancy complicated. Moreover in literature GDM and PGDM have been accused for respiratory morbidity in newborns. Diaphragm ultrasound (DUS) is useful and noninvasive method that provides an opportunity to examination of the diaphragmatic morphology and function. This study examined quality of fetal diaphragmatic contractions in pregnant women complicated with GDM and PGDM. Materials and Methods: A total of 105 volunteers separated into 3 groups; (1) GDM group (n=35), (2) PGDM group (n=35), and (3) healthy non-diabetic control group (n=35). Thickness of fetal diaphragm (DT), diaphragmatic excursion (DE), diaphragm thickening fraction (DTF) and costodiaphragmatic angle (CDA) was measured on the video frame during inspiration and expiration phases of respiration. Results: Especially PGDM group represented adversely affected diaphragm measurement parameters. DT inspiration, DT expiration, DE, CDA inspiration and DTF values were significantly different between PGDM and control group. Conclusions: Quality of fetal diaphragm movements affected in pregnancies complicated with GDM and PGDM. Prolonged duration of diabetes may have additional adverse effects on diaphragm morphology and its function.