This prospective study was conducted to compare risk factors and pregnancy outcomes between women with complete placenta previa and those with incomplete placenta previa diagnosed in mid-pregnancy. The study was carried out from April 2014 to December 2015, during which 70 patients with complete previa and 113 with incomplete previa between 20(+0) weeks and 25(+6) weeks of gestation were included. Maternal demographics and pregnancy outcomes were compared between the two groups. Comparisons between categorical variables were tested by chi-squared test and those between continuous variables by Student t test. Resolution of previa occurred in 87.43% of the studied women. The mean gestational age at resolution was 32.1 +/- 4.4 weeks. Incidence of maternal age 35 years and incidence of prior uterine operation 3 were high in women with complete previa (28.6% vs 8.8%, P=0.003; 28.6% vs. 8.8%, P=0.003). Resolution of previa occurred less often in complete previa group (74.3% vs. 95.6%, P=0.001). Women with complete previa admitted earlier (37.3 +/- 2.0 weeks 38.1 +/- 1.4 weeks, P=0.011) and delivered earlier (37.7 +/- 1.2 weeks vs. 38.3 +/- 1.4 weeks, P=0.025). Maternal age 35 years and prior uterine operation 3 increase the risk of complete previa in mid-pregnancy. Placenta previa is more likely to persist in women with complete previa than those with incomplete previa diagnosed in midpregnancy. What is more, women with complete previa in mid-pregnancy delivers earlier.