Guideline sources The following summarized guidelines for the evaluation and management of placenta previa are prepared by our editorial team based on guidelines from the Society of Obstetricians and Gynaecologists of Canada (SOGC 2020) and the Royal College of Obstetricians and Gynaecologists (RCOG 2019). 1 2 Guidelines 1. Screening and diagnosis Indications for screening: determine placental location during mid-pregnancy routine fetal U/S to identify women at risk of persisting placenta previa or a low-lying placenta. B Diagnosis: do not diagnose placenta previa or low-lying placenta < 18-20 weeks of gestation, and confirm the provisional diagnosis after > 32 weeks of gestation, or earlier if the clinical situation warrants. D 2. Classification and risk stratification Risk factors: https://web.pathway.md/diseases/recO1pqn0SOXKzsug 1/5 6/29/23, 11:12 PM Placenta previa Pathway Risk factors: Recognize that Cesarean delivery is associated with an increased risk of placenta previa in subsequent pregnancies and this risk rises as the number of prior C-sections increases. B Recognize that assisted reproductive technology and maternal smoking increase the risk of placenta previa. B Terminology: use the term placenta previa if the placenta lies directly over the internal os. Use the term low-lying placenta if the placental edge is < 20 mm from the internal os on transabdominal or transvaginal ultrasound for pregnancies > 16 weeks of gestation. B Risk stratification: recognize that all patients with placenta previa or low-lying placenta have an increased risk of a morbidly adherent placenta, particularly if they have had a prior Cesarean delivery. B Show 3 more 3. Diagnostic investigations Ultrasound: As per SOGC 2020 guidelines, obtain ultrasound to confirm placental location in patients with a low-lying placenta within 7-14 days before Cesarean delivery. B Show 2 more As per RCOG 2019 guidelines, obtain a follow-up ultrasound including transvaginal ultrasound at 32 weeks of gestation to diagnose persistent low-lying placenta and/or placenta previa if the placenta is thought to be low lying (< 20 mm from the internal os) or previa (covering the os) at the routine fetal U/S. B Show 3 more 4. Medical management Setting of care: As per SOGC 2020 guidelines: Offer outpatient management in patients with placenta previa in the absence of risk factors. B Consider offering in-hospital management in patients with placenta previa or low-lying placenta in the presence of risk factors or limited access to urgent obstetrical care. B As per RCOG 2019 guidelines, tailor antenatal care, including hospitalization, to individual patient's needs and social circumstances, such as distance between home and hospital and availability of transportation, previous bleeding episodes, hematology laboratory results, and acceptance of receiving donor blood or blood products. B Show 2 more Antenatal corticosteroids: As per SOGC 2020 guidelines, administer 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. B https://web.pathway.md/diseases/recO1pqn0SOXKzsug 2/5 6/29/23, 11:12 PM Placenta previa Pathway As per RCOG 2019 guidelines, administer a single course of antenatal corticosteroids between 34+0 and 35+6 weeks of gestation in patients with placenta previa or a low-lying placenta and before 34+0 weeks of gestation in patients at higher risk of preterm birth. B Tocolytics: As per SOGC 2020 guidelines, consider initiating tocolysis in patients with antepartum hemorrhage associated with uterine contractions to allow administration of corticosteroids or transfer of care, but not for prolongation of pregnancy. C As per RCOG 2019 guidelines: Consider initiating tocolysis in patients presenting with symptomatic placenta previa or a low-lying placenta for 48 hours to facilitate administration of antenatal corticosteroids. C Do not initiate tocolysis in an attempt to prolong gestation if delivery is indicated based on maternal or fetal concerns. D Management of anemia: prevent and treat anemia during the antenatal period in patients with placenta previa or a low-lying placenta as for any pregnant woman. B 5. Nonpharmacologic interventions Bed rest: advise patients with placenta previa to avoid bed rest or reduced activity. B Pelvic rest: advise patients with placenta previa to avoid sexual intercourse or insertion of foreign bodies in vagina or rectum. B 6. Therapeutic procedures Cervical cerclage: As per SOGC 2020 guidelines, consider performing cervical cerclage in patients with a short cervical length, particularly in association with antepartum hemorrhage, but not as a prophylactic measure in all patients with placenta previa. C As per RCOG 2019 guidelines, insufficient evidence to recommend cervical cerclage to reduce bleeding or prolong pregnancy, outside of a clinical trial. I Setting of delivery: As per SOGC 2020 guidelines, decide on the setting of delivery based on ultrasound assessment of placental location, risk factors, patient's history, and logistical factors, including available resources at the delivery unit. B As per RCOG 2019 guidelines, arrange delivery in a maternity unit with on-site blood transfusion services and access to critical care because placenta previa and anterior low- lying placenta carry a higher risk of massive obstetric hemorrhage and hysterectomy. B Timing of delivery: Consider offering late preterm (34+0 to 36+6 weeks of gestation) delivery in patients presenting with placenta previa or a low-lying placenta and a history of vaginal bleeding or other associated risk factors for preterm delivery. C Tailor delivery timing according to antenatal symptoms. Consider offering delivery between 36+0 and 37+0 weeks of gestation in patients presenting with uncomplicated placenta https://web.pathway.md/diseases/recO1pqn0SOXKzsug 3/5 6/29/23, 11:12 PM Placenta previa Pathway previa. B Mode of delivery: decide on the mode of delivery based on the clinical background, the patient's preferences, and supplemented by ultrasound findings, including the distance between the placental edge and the fetal head position relative to the leading edge of the placenta on trasnvaginal ultrasound in patients with a third trimester asymptomatic low-lying placenta. B Trial of labor: offer a trial of labor in patients with low-lying placenta where the placental edge is 11-20 mm from the cervical os. Consider offering a trial of labor in carefully selected patients where the placental edge is 10 mm from the cervical os. B 7. Perioperative care Regional anesthesia: As per SOGC 2020 guidelines, administer regional anesthesia as first-line anesthetic approach for the peripartum management of patients with placenta previa or low-lying placenta. B As per RCOG 2019 guidelines, prefer regional anesthesia over general anesthesia for Cesarean delivery in patients with placenta previa or a low-lying placenta, given its lower risks of hemorrhage. Inform patients with anterior placenta previa or a low-lying placenta that it may be necessary to convert to general anesthesia if required and ask to consent. B Intrapartum fluid resuscitation: ensure that rapid infusion and fluid warming devices are immediately available. B Peripartum blood transfusion: cooperate closely with the hospital transfusion laboratory for patients presenting with placenta previa or a low-lying placenta. B Show 2 more 8. Surgical interventions Cesarean section (indications): Offer Cesarean delivery in patients with placenta previa at 36 to 36 weeks of gestation in the presence of risk factors and at 37 to 37 weeks of gestation in the absence of risk factors. B Offer Cesarean delivery in patients with a low-lying placenta with the placental edge 10 mm from the cervical os at 37 to 37 weeks of gestation in the presence of risk factors and at 38 to 38 weeks of gestation in the absence of risk factors. B Cesarean section (surgical team): ensure that a planned C-section in patients with placenta previa is performed by an appropriately experienced surgeon, and a senior obstetrician (usually a consultant) and senior anesthetist (usually a consultant) are present within the delivery or theater suite. Alert senior obstetrician and senior anesthetist immediately to attend urgently if an emergency arises. B Cesarean section (technical considerations for surgery): consider performing vertical skin and/or uterine incisions if the fetus is in a transverse lie to avoid the placenta, particularly below 28 weeks of gestation. C https://web.pathway.md/diseases/recO1pqn0SOXKzsug 4/5 6/29/23, 11:12 PM Placenta previa Pathway Show 4 more 9. Patient education General counseling: counsel patients with asymptomatic placenta previa or a low-lying placenta in the third trimester regarding the risks of preterm delivery and obstetric hemorrhage and tailor care to individual needs. B Show 2 more Counseling before delivery: Discuss about the delivery with all patients with placenta previa and their partners before delivery. Review indications for blood transfusion and hysterectomy, and discuss openly and document any plans to decline blood or blood products. B Inform patients with anterior placenta previa or a low-lying placenta that it may be necessary to convert from regional anesthesia to general anesthesia if required and ask to consent. B References 1. Venu Jain, Hayley Bos, Emmanuel Bujold. Guideline No. 402 Diagnosis and Management of Placenta Previa. J Obstet Gynaecol Can. 2020 Jul;42 7 906 917.e1. Open 2. Jauniaux E, Alfirevic Z, Bhide AG et al. Placenta Praevia and Placenta Accreta: Diagnosis and Management: Green-top Guideline No. 27a. BJOG. 2019 Jan;126 1):e1-e48. Open 3. Royal College of Obstetricians and Gynaecologists. Blood Transfusion in Obstetrics. RCOG. 2015 May. Open https://web.pathway.md/diseases/recO1pqn0SOXKzsug 5/5