Benefits, Harms, and/or Costs
SUMMARY STATEMENTS (GRADE ratings in parentheses)
- 1All women with placenta previa or low-lying placenta have an increased risk of a morbidly adherent placenta, particularly those who have had a prior cesarean delivery (strong/moderate).
- 2In women with placenta previa or a low-lying placenta, presence of a marginal/velamentous cord insertion close to the cervical os or a succenturiate placental lobe increases the risk of vasa previa (strong/moderate).
- 3History of antepartum hemorrhage (first episode <29 weeks or recurrent episodes [≥3]), a thick placental edge covering (or close to) the cervical os, short cervical length (<3 cm with placenta previa, <2 cm with low-lying placenta), and a previous cesarean delivery are risk factors with an associated increased risk of urgent/preterm cesarean delivery (strong/moderate).
- 4In the absence of risk factors, outpatient management of women with placenta previa is safe (strong/moderate).
- 5Bed rest or reduced activity is not beneficial in women with placenta previa and can be potentially harmful. However, sexual intercourse/insertion of foreign bodies in vagina or rectum should be avoided (conditional [weak]/low).
- 6Preoperative bedside ultrasound assessment of placental location can be useful for planning of surgical technique and may reduce risk of intraoperative transection of placenta (conditional [weak]/low).
- 7Regional anaesthesia is safe and adequate as a first-line anaesthetic approach for the peripartum management of patients with placenta previa or low-lying placenta (conditional [weak]/low).
- 8When deciding the location of delivery, consider ultrasound assessment of placental location, any risk factors, the patient's history, and logistical factors, including available resources at the delivery unit (conditional [weak]/low).
RECOMMENDATIONS (GRADE ratings in parentheses)
- 1Classify placental location as placenta previa (placenta covering the cervical os), low-lying placenta (edge located ≤20 mm from cervical os), or normally located placenta (edge located >20 mm from cervical os) (strong/moderate).
- 2Diagnosis of placenta previa or low-lying placenta should not be made <18 to 20 weeks gestation, and the provisional diagnosis must be confirmed after >32 weeks gestation, or earlier if the clinical situation warrants. In women with a low-lying placenta, a recent ultrasound (within 7 to 14 days) should be used to confirm placental location prior to a cesarean delivery (strong/moderate).
- 3Assessment by transvaginal ultrasound is recommended in all cases where placenta previa or a low-lying placenta is present or suspected by transabdominal sonography, with attempt to clearly define placental location (including laterality), characteristics of placental edge (including thickness, presence of a marginal sinus), and associated findings (succenturiate lobe, cord insertion close to the cervix) (strong/moderate).
- 4In women with placenta previa or low-lying placenta and in the presence of risk factors or limited access to urgent obstetrical care, consider in-hospital management (strong/moderate).
- 5A cervical cerclage can be considered in women with a short cervical length, particularly in association with antepartum hemorrhage, but not as a prophylactic measure for all women with placenta previa (conditional [weak]/low).
- 6Administer antenatal corticosteroids for potential preterm delivery only if the risk of delivery within 7 days is very high and not solely because admission to the hospital is deemed necessary (strong/moderate).
- 7Tocolysis can be considered in women with antepartum hemorrhage associated with uterine contractions in order to allow administration of corticosteroids or transfer of care, but not for prolongation of pregnancy (conditional [weak]/low).
- 8Cesarean delivery is recommended in women with placenta previa at 360 to 366 weeks gestation in the presence of risk factors and at 370 to 376 weeks gestation in the absence of risk factors (strong/moderate).
- 9Cesarean delivery is recommended in women with a low-lying placenta with the placental edge ≤10 mm from the cervical os at 370 to 376 weeks gestation in the presence of risk factors and at 380 to 386 weeks gestation in the absence of risk factors (strong/moderate).
- 10A trial of labour is recommended in women with a low-lying placenta where the placental edge is 11 to 20 mm from the cervical os and can be considered in carefully selected women where the placental edge is ≤10 mm from the cervical os (strong/moderate).
Purchase one-time access:Academic & Personal: 24 hour online accessCorporate R&D Professionals: 24 hour online access
One-time access price info
- For academic or personal research use, select 'Academic and Personal'
- For corporate R&D use, select 'Corporate R&D Professionals'
Subscribe:Subscribe to Journal of Obstetrics and Gynaecology Canada
- Etiology and risk factors for placenta previa: an overview and meta-analysis of observational studies.J Matern Fetal Neonatal Med. 2003; 13: 175-190
- Prevalence of placenta praevia by world region: a systematic review and meta-analysis.Trop Med Int Health. 2013; 18: 712-724
- Natural history of placenta previa in twins.Obstet Gynecol. 2014; 123: 1070-1082
- The association of placenta previa and assisted reproductive techniques: a meta-analysis.J Matern Fetal Neonatal Med. 2018; 31: 1940-1947
- Toward consistent terminology of placental location.Semin Perinatol. 2013; 37: 375-379
- Fetal imaging: executive summary of a joint Eunice Kennedy Shriver National Institute of Child Health and Human Development, Society for Maternal-Fetal Medicine, American Institute of Ultrasound in Medicine, American College of Obstetricians and Gynecologists, American College of Radiology, Society for Pediatric Radiology, and Society of Radiologists in Ultrasound Fetal Imaging workshop.Am J Obstet Gynecol. 2014; 210: 387-397
- Placental edge to internal os distance in the late third trimester and mode of delivery in placenta praevia.BJOG. 2003; 110: 860-864
- FIGO position paper: how to stop the caesarean section epidemic.Lancet. 2018; 392: 1286-1287
- Previous prelabor or intrapartum cesarean delivery and risk of placenta previa.Am J Obstet Gynecol. 2015; 212: 669.e1-669.e6
- Incidence of and risk indicators for vasa praevia: a systematic review.BJOG. 2016; 123: 1278-1287
- The diagnosis and management of morbidly adherent placenta.Semin Perinatol. 2018; 42: 49-58
- Placental implantation abnormalities and risk of preterm delivery: a systematic review and metaanalysis.Am J Obstet Gynecol. 2015; 213: S78-S90
- Abnormal placentation: Placenta previa, vasa previa, and placenta accreta.Obstet Gynecol. 2015; 126: 654-668
- Analysis of the ultrasonographic findings predictive of vasa previa.Prenat Diagn. 2010; 30: 1121-1125
- Difference in migration of placenta according to the location and type of placenta previa.J Clin Ultrasound. 2008; 36: 79-84
- Third-trimester transvaginal ultrasonography in placenta previa: does the shape of the lower placental edge predict clinical outcome?.Ultrasound Obstet Gynecol. 2001; 18: 103-108
- Does cervical length and the lower placental edge thickness measurement correlates with clinical outcome in cases of complete placenta previa?.Arch Gynecol Obstet. 2011; 284: 867-873
- Rupture of the marginal sinus of the placenta.J Am Med Assoc. 1958; 166: 476-478
- Can ultrasonography of the placenta previa predict antenatal bleeding?.J Clin Ultrasound. 2011; 39: 458-462
- Planned vaginal delivery versus planned cesarean delivery in cases of low-lying placenta.J Matern Fetal Neonatal Med. 2017; 30: 618-622
- Anticipation of uterine bleeding in placenta previa based on vaginal sonographic evaluation.Gynaecol Obstet Invest. 2002; 54: 37-42
- Predicting the route of delivery in women with low-lying placenta using transvaginal ultrasonography: significance of placental migration and marginal sinus.Gynecol Obstet Invest. 2012; 73: 217-222
- Screening, diagnosis and management of placenta accreta spectrum disorders.J Obstet Gynecol Can. 2019; 41: 1035-1049
- Guidelines for the management of vasa previa.J Obstet Gynaecol Can. 2009; 31: 748-753
- The relevance of placental location at 20-23 gestational weeks for prediction of placenta previa at delivery: evaluation of 8650 cases.Ultrasound Obstet Gynecol. 2001; 17: 496-501
- Translabial ultrasonography and placenta previa: does measurement of the os-placenta distance predict outcome?.J Ultrasound Med. 1996; 15: 441-446
- Confirming the safety of transvaginal sonography in patients suspected of placenta previa.Obstet Gynecol. 1993; 81: 742-744
- Accuracy and safety of transvaginal sonographic placental localization.Obstet Gynecol. 1990; 76: 759-762
- Transvaginal ultrasound: does it help in the diagnosis of placenta previa?.Ultrasound Obstet Gynecol. 1992; 2: 256-260
- Transvaginal ultrasonography in predicting placenta previa at delivery: a longitudinal study.Ultrasound Obstet Gynecol. 2002; 20: 356-359
- Persistence of placenta previa according to gestational age at ultrasound detection.Obstet Gynecol. 2002; 99: 692-697
- Placenta previa in the second trimester: sonographic and clinical factors associated with its resolution.Am J Perinatol. 2011; 28: 735-739
- Outcomes of pregnancies with a low-lying placenta diagnosed on second-trimester sonography.J Ultrasound Med. 2014; 33: 691-696
- Transvaginal ultrasonography at 18-23 weeks in predicting placenta previa at delivery.Ultrasound Obstet Gynecol. 1998; 12: 422-425
- Diagnosis of low-lying placenta: can migration in the third trimester predict outcome?.Ultrasound Obstet Gynecol. 2001; 18: 100-102
- Cervical length and risk of antepartum bleeding in women with complete placenta previa.Ultrasound Obstet Gynecol. 2009; 33: 209-212
- Ultrasonographic cervical length and risk of hemorrhage in pregnancies with placenta previa.Obstet Gynecol. 2010; 116: 595-600
- Consecutive cervical length measurements as a predictor of preterm cesarean section in complete placenta previa.J Clin Ultrasound. 2015; 43: 17-22
- Effect of a low-lying placenta on delivery outcome.Ultrasound Obstet Gynecol. 2009; 33: 204-208
- Placenta previa: distance to internal os and mode of delivery.Am J Obstet Gynecol. 2009; 201: 266.e1-266.e5
- Interventions for suspected placenta praevia.Cochrane Database Syst Rev. 2003; CD001998
- Cervical cerclage for the temporary treatment of patients with placenta previa.Obstet Gynecol. 1988; 71: 545-548
- Cervical cerclage: an alternative for the management of placenta previa?.Am J Obstet Gynecol. 1998; 179: 122-125
- No. 373-Cervical Insufficiency and Cervical Cerclage.J Obstet Gynaecol Can. 2019; 41: 233-247
- Placenta previa: antepartum conservative management, inpatient versus outpatient.Am J Obstet Gynecol. 1994; 170: 1683-1686
- Management of the symptomatic placenta previa: a randomized, controlled trial of inpatient versus outpatient expectant management.Am J Obstet Gynecol. 1996; 175: 806-811
- A score to predict the risk of emergency caesarean delivery in women with antepartum bleeding and placenta praevia.Eur J Obstet Gynecol Reprod Biol. 2015; 195: 173-176
- Predictors for emergency cesarean delivery in women with placenta previa.Am J Perinatol. 2016; 33: 1407-1414
- Effects of exercise during pregnancy in women with short cervix: Secondary analysis from the Italian Pessary Trial in singletons.Eur J Obstet Gynecol Reprod Biol. 2018; 229: 132-136
- Physical activity and the risk of preterm birth: a systematic review and meta-analysis of epidemiological studies.BJOG. 2017; 124: 1816-1826
- Perceptions of bed rest by women with high-risk pregnancies: a comparison between home and hospital.Birth. 1998; 25: 252-258
- Antenatal corticosteroid therapy for improving neonatal outcomes.J Obstet Gynaecol Can. 2018; 40: 1219-1239
- The effect of tocolytic use in the management of symptomatic placenta previa.Am J Obstet Gynecol. 1995; 172: 1770
- Tocolytic therapy in conservative management of symptomatic placenta previa.Int J Gynaecol Obstet. 2004; 84: 109
- Maintenance tocolytics for preterm symptomatic placenta previa: a review.Am J Perinatol. 2011; 28: 45-50
- Maintenance nifedipine therapy for preterm symptomatic placenta previa: a randomized, multicenter, double-blind, placebo-controlled trial.PLoS One. 2017; 12e0173717
- Is tocolysis safe in the management of third-trimester bleeding?.Am J Obstet Gynecol. 1999; 180: 1572-1578
- Usefulness of coagulation studies and blood banking in patients with symptomatic placenta previa.Am J Perinatol. 1997; 14: 601-604
- Placenta previa and maternal hemorrhagic morbidity.J Matern Fetal Neonatal Med. 2018; 31: 494-499
- Amount of hemorrhage during vaginal delivery correlates with length from placental edge to external os in cases with low-lying placenta whose length between placental edge and internal os was 1-2 cm.J Obstet Gynaecol Res. 2012; 38: 1041-1045
- Evaluating the safety of labour in women with a placental edge 11 to 20 mm from the internal cervical Os.J Obstet Gynaecol Can. 2014; 36: 674-677
- Bleeding complications in pregnancies with low-lying placenta.J Matern Fetal Neonatal Med. 2016; 29: 1367-1371
- Transecting versus avoiding incision of the anterior placenta previa during cesarean delivery.Int J Gynaecol Obstet. 2015; 128: 44-47
- Comparison of general and epidural anesthesia in elective cesarean section for placenta previa totalis: maternal hemodynamics, blood loss and neonatal outcome.Int J Obstet Anesth. 2003; 12: 12-16
- Mode of anesthesia and clinical outcomes of patients undergoing Cesarean delivery for invasive placentation: a retrospective cohort study of 50 consecutive cases.Can J Anaesth. 2016; 63: 1233-1244
- Timing of indicated late-preterm and early-term birth.Obstet Gynecol. 2011; 118: 323-333
- A late-preterm, early-term stratified analysis of neonatal outcomes by gestational age in placenta previa: defining the optimal timing for delivery.J Matern Fetal Neonatal Med. 2015; 28: 1756-1761
- Using ultrasound in the clinical management of placental implantation abnormalities.Am J Obstet Gynecol. 2015; 213: S70-S77
- Neonatal outcomes of elective early-term births after demonstrated fetal lung maturity.Am J Obstet Gynecol. 2018; 219: 296.e1-296.e8
- Placenta previa: aggressive expectant management.Am J Obstet Gynecol. 1984; 150: 15
- An update on the risk factors for and management of obstetric haemorrhage.Womens Health (Lond). 2017; 13: 34-40
- Prevention and management of postpartum hemorrhage: a comparison of 4 national guidelines.Am J Obstet Gynecol. 2015; 213: 76.e1-76.e10
- Development of a scoring system to predict massive postpartum transfusion in placenta previa totalis.J Anesth. 2017; 31: 593-600
This document reflects emerging clinical and scientific advances as of the publication date and is subject to change. The information is not meant to dictate an exclusive course of treatment or procedure. Institutions are free to amend the recommendations. The SOGC suggests, however, that they adequately document any such amendments.
Informed consent: Everyone has the right and responsibility to make informed decisions about their care together with their health care providers. In order to facilitate this, the SOGC recommends that they provide their patients information and support that is evidence-based, culturally appropriate, and personalized.
Language and inclusivity: This document uses gendered language in order to facilitate plain language writing but is meant to be inclusive of all individuals, including those who do not identify as a woman/female. The SOGC recognizes and respects the rights of all people for whom the information in this document may apply, including but not limited to transgender, non-binary, and intersex people. The SOGC encourages health care providers to engage in respectful conversation with their patients about their gender identity and preferred gender pronouns and to apply these guidelines in a way that is sensitive to each person's needs.
Copyright: The contents of this document cannot be reproduced in any form, in whole or in part, without prior written permission of the publisher of the Journal of Obstetrics and Gynaecology Canada.