Placenta Previa

Chapter 216 Placenta Previa



INTRODUCTION



Description: Placenta previa is implantation of the placenta in a location that leaves part or all of the cervical os covered. This is associated with potentially catastrophic maternal bleeding and obstruction of the uterine outlet. Several degrees are recognized: total, partial, marginal, and low-lying placenta. These degrees may vary with cervical dilation or gestational age.

Prevalence: Seen in 0.3% to 0.5% of deliveries.

Predominant Age: Reproductive, average age 29 years.

Genetics: No genetic pattern.


ETIOLOGY AND PATHOGENESIS



Causes: Implantation by the zygote low in the uterine cavity (in close proximity to the cervical os). Defective decidual vascularization, resulting from inflammation or atrophy, has been implicated.

Risk Factors: Multiparity, advanced maternal age (>35: 1% of deliveries, >40: 2%), prior cesarean delivery (two to five times increase), induced abortion, smoking (2-fold increase), cocaine use, multiple gestation, high altitude, and prior abortion.


CLINICAL CHARACTERISTICS



Signs and Symptoms



• Painless vaginal bleeding (70%, generally not present until late second or early third trimester); may be catastrophic in amount, although initial episodes are rarely fatal; blood is maternal in origin

• Uterine hyperactivity possibly present with bleeding (20%)

• Heavy or prolonged bleeding after delivery


DIAGNOSTIC APPROACH



Differential Diagnosis



• Bloody show of early labor

• Placental abruption

• Vasa previa

• Low-lying placenta


Associated Conditions: Placenta accreta (15% to 25% of patients), increta, or percreta and prematurity.


Workup and Evaluation



Laboratory: Complete blood count, type and cross-match blood products for possible replacement.

Imaging:

Related posts:

  1. Anemia
  2. Toxic Shock Syndrome
  3. Uterine Anomalies: Bicornuate, Septate, and Unicornuate Uterus
  4. Cervical Cancer

Stay updated, free articles. Join our Telegram channel
Tags:
Jun 6, 2016 | Posted by in GYNECOLOGY | Comments Off on Placenta Previa

Full access? Get Clinical Tree
Get Clinical Tree app for offline access