OB Nightmares: Third Trimester Vaginal Bleeding

Third-trimester vaginal bleeding is an obstetric emergency until maternal and fetal stability are proven. Painful bleeding points toward abruption or labor, while painless bleeding raises concern for placenta previa, accreta spectrum, or vasa previa; the first fork in the ED is resuscitation and OR readiness versus ultrasound-first evaluation.

Third-Trimester Bleeding Evaluation

• Maternal and fetal stability: The first priority is vital signs for both mother and baby; if either is unstable, involve OB immediately, prepare for the OR, and start hemorrhage resuscitation.
• Blood loss appearance trap: Visible bleeding does not predict severity in late-pregnancy hemorrhage, so even spotting can accompany a dangerous maternal or fetal condition.
• Painful versus painless pattern: Painful bleeding favors placental abruption or labor, while painless bleeding should push placenta previa, accreta, and vasa previa high on the differential.
• Ultrasound before pelvic exam: Placenta previa should be excluded with ultrasound before a pelvic exam in painless bleeding, because the wrong exam can worsen hemorrhage. We get into the bedside exceptions in the episode.
• Abruption imaging limitation: Ultrasound may show placental abruption, but a normal study does not rule it out, making clinical assessment more important than imaging reassurance.

Initial ED Management Priorities

• OR versus ED pathway: Unstable patients need parallel resuscitation and cesarean readiness, with OB activation, large-bore IV access, labs, and massive transfusion protocol early.
• Stable patient tempo: If mother and baby are stable, management shifts from immediate delivery to defining the cause, checking for labor, and coordinating next steps with OB.
• Fetal benefit medications: When delivery may be imminent but not emergent, antenatal betamethasone, magnesium for neuroprotection, and antibiotics for selected patients become the key early therapies.
• Speculum and labor clues: A gentle speculum exam can help identify bulging membranes or fetal parts when labor is suspected, but exam sequencing depends on whether previa is still on the table.
• Tocolytic nuance: Tocolytics may help in placenta previa but can be contraindicated in abruption or impending delivery; that decision is usually safest in direct consultation with OB, and we walk through the practical distinctions in the chapter.

References:

1. Norwitz ER, et al. Overview of the etiology and evaluation of bleeding in pregnancy. Ed. Barrs, VA. UpToDate, Jul 2021. Link.
2. Gyamfi-Bannerman C. Society for Maternal-Fetal Medicine (SMFM) Consult Series #44: Management of bleeding in the late preterm period. Am J Obstet Gynecol. 2018;218(1):B2-B8. PMID: 29079144.