SEARCH RESULTS FOR: Placenta-Previa

Placenta-Previa

Placenta Previa: Pathogenesis and Clinical Findings Authors: Wendy Yao, Yan Yu* Reviewers: Danielle Chang, Crystal Liu, Aysah Amath* * MD at time of publication Note on Physical Exam: • Do not perform bimanual exam during vaginal bleed until placenta previa is ruled out (2nd trimester onwards) • If patient presents with bleeding, a pelvic exam = risk of damaging placentaàmore bleeding • Use transvaginal ultrasound to confirm location of placenta Previous C/S Multiple gestation Maternal smoking Placenta Previa Presence of placental tissue that extends over the internal cervical os. (Pathogenesis unknown; preceding textboxes are risk factors only) Previous placenta previa Increased maternal age Increased parity Total placenta previa Placenta completely covers the cervix Partial placenta previa Placenta covers cervix partially Marginal placenta previa Placenta near the edge of the cervix Diagnosed early in pregnancy on routine abdominal ultrasound at 18-20 weeks Stretching of lower segment of uterus during 3rd trimester OR Alternate scenario: One scenario: This stretching elongates the space between the cervix and the placenta, relocating the stationary lower edge of the placenta away from the cervical os Placenta previa resolves on its own Reassuring: Placenta >2cm from cervical os on ultrasound This stretching fails to move the placental away from the cervical os Previa persists as uterus changes in preparation for labour: Thinning of the lower segment of the uterus Uterine contractions Shearing forces to the placental attachment site Painless bright red vaginal bleeding (90%) ↑ risk of clinically significant hemorrhage Cervix becomes thinner (effaced) and opens (dilates) Bleeding limits oxygen delivery to placenta, injuring placental tissue Tissue injuryàActivates intracellular G-protein signalling pathways Release of stored intracellular calcium àmyometrial contraction Uterine contraction and bleeding (10%) Legend: Pathophysiology Mechanism Sign/Symptom/Lab Finding Complications Published May 2, 2020 on www.thecalgaryguide.com