From the Guidelines
Placenta previa typically presents with painless, bright red vaginal bleeding in the second or third trimester of pregnancy, and the condition is diagnosed definitively through ultrasound, which shows the placenta covering part or all of the cervical opening 1. The bleeding often starts suddenly without any triggering event and may stop on its own, only to recur later with increasing severity. Some women experience no symptoms and the condition is discovered during routine ultrasound. Other signs include:
- Abnormal fetal positioning such as breech or transverse lie due to the placenta occupying the lower uterine segment
- Profuse and life-threatening bleeding in severe cases, requiring immediate medical attention The bleeding occurs because as the lower part of the uterus stretches and thins in preparation for labor, blood vessels connecting the placenta to the uterine wall may tear. Women with placenta previa should seek emergency care for any vaginal bleeding during pregnancy, avoid sexual intercourse and vaginal examinations, and may require bed rest or hospitalization depending on the severity of bleeding and gestational age. Transabdominal US is the mainstay of obstetrical imaging, and transvaginal US is particularly helpful in evaluating cervical-related causes of second and third trimester vaginal bleeding 1. The primary goal of transabdominal US in the setting of painless bleeding is to exclude pathologic etiologies for the bleeding, and transvaginal US is frequently necessary for evaluation of painless vaginal bleeding, especially if transabdominal US is inconclusive or inadequate 1. Accurate antenatal diagnosis is needed to plan for an appropriate delivery strategy at an experienced center in order to reduce maternal morbidity, and the American Congress of Obstetricians and Gynecologists (ACOG) and FIGO recommend planned cesarean delivery with or without hysterectomy depending on the suspected severity of PASD around 34 to 38 weeks 1.
From the Research
Signs of Placenta Previa
The signs of placenta previa include:
- Painless vaginal bleeding, which can be sudden and severe 2, 3, 4
- Contractions, which can be a symptom in some cases 3
- Abnormal placental placement in the lower uterine segment, obstructing the cervical opening, which can be diagnosed by transvaginal ultrasonography 2
- Risk factors such as prior cesarean delivery, pregnancy termination, intrauterine surgery, smoking, multifetal gestation, increasing parity, and maternal age, which can increase the likelihood of developing placenta previa 2
Diagnostic Modalities
The diagnostic modality of choice for placenta previa is:
- Transvaginal ultrasonography, which can help diagnose the condition and determine the distance between the placenta and the cervical os 2
- Ultrasound examination, which can also help diagnose vasa previa and other related conditions 2
Management Strategies
Management strategies for placenta previa include:
- Cesarean delivery, which is often necessary for women with complete placenta previa 2
- Regional anesthesia for cesarean delivery, which is safe for women with placenta previa 2
- Preventive uterine artery embolization (UAE) before placental expulsion, which can help reduce postpartum bleeding in cases of placenta previa totalis 5
- Tocolytic use, which can help prolong pregnancy and increase birth weight in cases of symptomatic preterm placenta previa 6