Objective: The primary objective was to examine the association between previous uterine operation and placenta previa. The secondary objectives were to study the association between cesarean hysterectomy and placenta previa and to evaluate the maternal and neonatal outcomes of placenta previa

Material and Method: All medical records of placenta previa patients delivered at King Chulalongkorn Memorial Hospital between January 2006 and December 2008 were reviewed (215 records). Two hundred and six records were enrolled and nine records were excluded. Controls were selected by matching the first following patients delivered by cesarean section and none had a previa at delivery the same day as the index case. Student t-test, Mann-Whitney U-test and Chi-square test were used when appropriate. Odd ratio was calculated for evaluation of risk factors of placenta previa.

Results: Previous uterine operations were found in the placenta previa group more than the control group but with no statistically significant difference {previous c/s (18.9% vs. 16.5%, p = 0.6), previous myomectomy (1.5% vs. 0%, p = 0.1) and previous dilatation and curettage (17.5% vs. 11.2%, p = 0.1)}. Odd ratio of previous cesarean section and previous dilatation and curettage for placenta previa was 1.2 (95% CI 0.7 to 1.9) and 1.7 (95% CI 0.9 to 2.9), respectively. In the placenta previa group, there were more statistically significant differences and poorer maternal outcomes than in  the control  group, including blood loss (1,306.1 ml vs. 528.9 ml, p < 0.001), postpartum hemorrhage (9.2% vs. 0.5%, p < 0.001), cesarean hysterectomy (7.3% vs. 0%, p < 0.001), blood transfusion (27.7% vs. 1%, p < 0.001) and more poorer neonatal outcomes than in the control group, including preterm birth (30.5% vs. 3.9%, p < 0.001), lower birth weight (2,777.9 g vs. 3,186.3 g, p < 0.001), and lower APGAR score at first minute (8.24 vs. 8.66, p = 0.004) and at fifth minute (9.45 vs. 9.73, p = 0.035).

Conclusion: In the present study, the majority of patients with placenta previa have no association with previous uterine operation. However, it is potentially life-threatening to the mother and frequently results in high perinatal morbidity.

Keywords: Placenta previa, Risk factors, Previous cesarean section, Previous abortion, Previous myomectomy, Previous uterine operation