Which second trimester placenta previa remains a placenta previa in the third trimester: A prospective cohort study

Abstract

ObjectiveThe far majority of women with a placenta previa in the second trimester will no longer have a placenta that overlies the internal os in the third trimester. Women with a placenta previa in the third trimester are at risk for complication such as preterm birth and blood loss. Four counselling purposes we aim to identify which women with a second trimester placenta previa have a low-risk and a high-risk for persistence of the placenta previa. Study designA prospective cohort study of women with a placenta previa in the second trimester between 2014 and 2019. The odds for having a placenta previa in the third trimester were calculated for different baseline characteristics. Multilevel likelihood ratios for ranges of the placenta overlying the internal os in the second trimester and the corresponding ROC curve were calculated to identify the optimal cut-off values. ResultsWe included 313 women with a placenta previa in the second trimester. The placenta was more frequently located on the posterior wall (62 %) than on the anterior wall (38 %). At evaluation in the third trimester, 37 women (14 %) still had a placenta previa. Women with a larger distance of the placenta overlying the internal os, women having a previous cesarean delivery and women after a conception with assisted reproductive technique had a significant higher risk of placenta previa persistence (p-values <0.001). Women with a placenta overlying less than 14 mm can be considered as low-risk, indicated by a likelihood ratio of 0. Women with a placenta with more than 55 mm overlap can be considered as high-risk, indicated a the likelihood ratio of ∞. ConclusionThe majority of the second trimester placenta previa will no longer overly the internal os in the third trimester. Placenta previa persistence is associated with the distance overlying the internal os, a previous cesarean delivery and assisted reproductive techniques. In the second trimester, women can be identified as low-risk and high-risk for persistence of placenta previa. This can be used for risk stratification, counselling and individualized care for women with a second trimester placenta previa.