OBJECTIVE: The aim of this study was to assess the association between maternal weight gain and placenta morphology in the complete placenta previa pregnancies. PATIENTS AND METHODS: This was a prospective clinical cohort study. Pregnancy weight gain was defined as the difference between delivery and at first trimester. Morphological parameters, including placenta length, breadth, thickness, length-breadth. surface area, weight. and fetoplacental weight ratio, were direct measured delivery. RESULTS: Eighty-five women were included in this study. Maternal weight gain was 11.12 +/- 3.95 kg. Placenta length, breadth, thickness, length-breadth, surface area, weight and fetoplacental weight ratio were 19.42 +/- 1.97 cm, 18.29 +/- 1.80 cm. 2.18 +/- 0.38 cm, 1.13 +/- 0.80 cm. 281.60 +/- 57.23 cm(2). 569.05 +/- 118.77 g. and 4.88 +/- 0.88, respectively. Correlation analysis showed that there was a positive correlation between maternal weight gain and placenta length (r = 0.261, p = 0.016), placenta breadth (r = 0.239, p = 0.028), and placenta surface area (r = 0.254, p = 0.019). In the linear regression model, maternal weight gain was significantly associated with placenta length [beta (95% CI): 0.130 (0.025-0.236)], breadth [beta (95% CI): 0.109 (0.012-0.205)]. and surface area (beta (95%CI): 3.677 (0.615-6.739)]. The results were still stable after adjusting for pre-pregnancy weight. CONCLUSIONS: Maternal weight gain in pregnancy was associated with placental length, placental breadth, and placental surface area in a complete placenta previa pregnancies. Considering the single center data. further studies are needed to recognize the significance of the association analyzed in our study.