This study shows that the length of your cervix and the thickness of your placental edge can be indictors for your risk of bleeding. It looks like 22 of the 54 previa cases actually bled, so still less than 50%.
Does cervical length and the lower placental edge thickness measurement correlates with clinical outcome in cases of complete placenta previa?
Authors :Zaitoun MM; El Behery MM; Abd El Hameed AA; Soliman BS
Author Address:Zagazig University, Zagazig, Egypt.Source:Archives Of Gynecology And Obstetrics [Arch Gynecol Obstet] 2011 Oct; Vol. 284 (4), pp. 867-73.
Objectives: To evaluate the effectiveness of cervical length and the lower placental edge thickness measurement in predicting the risk of antepartum hemorrhage (APH) and emergency preterm cesarean delivery in women with complete placenta previa.
Methods: Fifty-four cases with confirmed diagnosis of complete placenta previa in third-trimester were subjected to transvaginal sonographic measurement of cervical length and lower placental edge thickness and correlated this to clinical outcome with regards to gestational age at delivery, ante partum hemorrhage, emergency cesarean section before 36 weeks due to massive hemorrhage and neonatal birth weight.
Results: Antepartum bleeding and emergency cesarean section rate before 36 weeks due to massivebleeding were significantly higher in cases with thick lower placental edge or central placenta than cases with thin lower placental edge [16 cases (53.3%) vs. 5 cases (20.8%)] for the former and [14 cases (46.6%) vs. 4 cases (16.6%) for the later]. Antepartum bleeding was observed in 18 cases (51.4%) when cervical length measurements ≤30 mm of whom 16 cases (88.9%) had showed severe attack necessitated emergency cesarean delivery before 36 weeks versus 4 cases (21.1%) with cervical length ≥30 mm. By combining cervical length with lower placental edge thickness measurement sensitivity, specificity, positive predictive value (PPV) negative predictive value (NPV) and accuracy increased to 83.3, 78.4, 53.4, 79.8 and 89.7%, respectively for the prediction of antepartum bleeding and emergency cesarean section <36 weeks using receiver-operating characteristics curve with area under the curve 0.882.
Conclusion: Short cervical length at cut-off value ≤30 mm and increased lower placental edge thickness measurements may predict with high accuracy the risk of APH and emergency preterm cesarean delivery in patients with complete placenta previa.