Pregnancy, Childbirth & Puerperium

Placenta previa: diagnosis and management

Clinical Overview and When to Suspect Placenta Previa

— Complete previa: placenta fully covers the internal os

— Low-lying placenta: placental edge <2 cm from the os but not covering it

— Older terms "marginal" and "partial" have been retired by SMFM/ACOG in favor of these two categories

— Painless, bright red vaginal bleeding in the second or third trimester (classic stem)

— Incidental finding on routine 18–22 week anatomy ultrasound (most common modern presentation)

— Malpresentation at term (transverse, breech, or unstable lie) because the placenta blocks engagement

— Postcoital bleeding in late pregnancy without contractions or trauma

— Prior cesarean delivery (risk rises with each one; also raises accreta risk)

— Prior previa (4–8% recurrence)

— Multiparity, advanced maternal age (>35)

— Prior uterine surgery (myomectomy, D&C, endometrial ablation)

— Multifetal gestation, ART/IVF conception

— Smoking and cocaine use (impaired uteroplacental perfusion → larger placental surface area)

Definition: Placenta previa is implantation of the placenta over or within 2 cm of the internal cervical os in the second half of pregnancy

Epidemiology: ~1 in 200 pregnancies at term; incidence rising due to higher cesarean and ART rates

Pathophysiology: Abnormal implantation in the lower uterine segment → as the segment thins and the cervix effaces in the third trimester, exposed villi shear → maternal venous sinus bleeding

When to suspect previa on Step 3:

Major risk factors:

Board pearl: The triad that should immediately trigger previa on the exam is painless + bright red + third-trimester bleeding — contrast this with the painful, dark, often concealed bleeding of abruption. Never perform a digital cervical exam until previa has been excluded by ultrasound.

Step 3 management: When a pregnant patient calls the office reporting any third-trimester vaginal bleeding, the answer is send to L&D for evaluation, not in-office speculum exam, and obtain transabdominal then transvaginal ultrasound before any digital exam.

Presentation Patterns and Key History

— Sudden onset painless, bright red vaginal bleeding, often after 28 weeks

— First "sentinel bleed" is typically self-limited and not catastrophic; subsequent bleeds tend to be heavier

— No associated uterine tenderness; contractions, if present, are usually a secondary response to blood in the uterus

— Bleeding may follow intercourse, vaginal exam, or exercise but can be spontaneous

— Detected at routine 18–22 week anatomy scan as low-lying placenta or previa

— Most low-lying placentas (~90%) and many previas resolve by the third trimester via "placental migration" (differential growth of the lower uterine segment, not actual movement)

— Persistent previa at ≥32 weeks is unlikely to resolve

— Gestational age — critical for management decisions

— Quantity and character of bleeding (pad count, clots, color)

— Pain, contractions, back pain → suggests abruption or labor instead

— Trauma, intercourse, recent cervical exam

— Fetal movement

— Obstetric history: prior cesareans, prior previa, prior D&C, prior myomectomy

— Tobacco, cocaine, prior placenta accreta

— Rh status (for anti-D prophylaxis if bleeding)

— Regular painful contractions + cervical change suggest preterm labor superimposed on previa

— Tocolysis becomes a nuanced decision in this setting (see later chunks)

— Painless bleeding with rupture of membranes and acute fetal distress (sinusoidal tracing, bradycardia) is vasa previa, not placenta previa — fetal blood loss, not maternal

Classic third-trimester presentation:

Asymptomatic presentation (modern majority):

Key history questions on a Step 3 stem:

Distinguishing concurrent labor:

Vasa previa pitfall:

Key distinction: Painless bright red bleeding = previa; painful dark bleeding ± rigid tender uterus = abruption; painless bleeding with ROM + fetal bradycardia = vasa previa; bleeding with shock out of proportion to visible loss in a patient with prior cesarean = consider uterine rupture or accreta spectrum.

Board pearl: A patient with persistent previa at term who reports a "small bleed that stopped" still requires inpatient admission for observation — the next bleed is usually worse.

Physical Exam Findings and Hemodynamic Assessment

— Airway, breathing, circulation with two large-bore IVs

— Vital signs trending — pregnant patients can lose 30–35% of blood volume before becoming overtly hypotensive due to physiologic hypervolemia

— Tilt the patient left lateral to relieve aortocaval compression

— Estimate blood loss by pad/chux weight, not visual gestalt alone

— Soft, nontender uterus — hallmark of previa

— Fundal height appropriate; malpresentation (transverse lie, breech, high floating head) is a clue

— Leopold maneuvers may reveal unengaged presenting part because the placenta occupies the lower segment

— A rigid, tender, "woody" uterus with concealed bleeding points to abruption instead

— Do NOT perform a digital cervical exam until ultrasound has excluded previa

— Digital exam can dislodge clot from exposed sinuses and provoke catastrophic hemorrhage

— Gentle sterile speculum exam is acceptable after ultrasound to evaluate for cervical, vaginal, or local sources and to assess bleeding volume

— If previa is confirmed and delivery is needed, proceed straight to cesarean — no digital exam

— Continuous external fetal monitoring on arrival

— Category I tracing is reassuring; recurrent decelerations or bradycardia suggest fetal compromise from maternal hypovolemia, abruption, or vasa previa

— Tocometry to detect contractions

— SBP <90, HR >120, lactate >4, ongoing brisk bleeding

— Shock index (HR/SBP) >0.9 is an early warning in obstetric hemorrhage

General assessment priorities (ABC first):

Abdominal exam:

Pelvic exam — the cardinal rule:

Fetal assessment:

Hemodynamic red flags requiring activation of massive transfusion protocol:

CCS pearl: On a CCS-style case, your initial orders for third-trimester bleeding should look like: continuous fetal monitoring, two large-bore IVs, CBC, type & crossmatch 2–4 units PRBCs, coagulation panel, fibrinogen, Kleihauer-Betke if Rh-negative, RhoGAM if indicated, and bedside ultrasound — before any pelvic exam.

Board pearl: The absence of uterine tenderness is just as diagnostically powerful as the presence of bleeding when distinguishing previa from abruption.

Diagnostic Workup — Initial Labs and Imaging

— CBC — baseline hemoglobin/hematocrit and platelets

— Type and screen, with crossmatch for 2–4 units PRBCs if active bleeding

— Coagulation panel: PT/INR, aPTT, fibrinogen (fibrinogen <200 mg/dL is abnormal in pregnancy and an early DIC marker)

— Kleihauer-Betke test in Rh-negative patients to quantify fetomaternal hemorrhage and dose anti-D Ig appropriately

— Basic metabolic panel; consider lactate if shock suspected

— Urinalysis to rule out UTI as a coincident cause of preterm contractions

— Give 300 mcg IM to Rh-negative, unsensitized patients with any bleeding episode

— Repeat dose if Kleihauer-Betke suggests >30 mL of fetal blood

— Identifies placental location relative to the internal os

— Sensitivity ~95% but can miss posterior previas; full bladder can falsely suggest previa

— Sufficient for screening; must be confirmed by transvaginal ultrasound

— Safe in previa — the probe is angled and does not contact the cervix

— Superior sensitivity and specificity for localizing the placental edge

— Measures distance from placental edge to internal os in millimeters

— Quantifies cervical length, which predicts hemorrhage risk and preterm delivery

— Placental edge covering the os = placenta previa → cesarean delivery

— Edge 1–20 mm from os = low-lying placenta → cesarean usually preferred; individualized

— Edge >20 mm from os = vaginal delivery generally safe

Initial laboratory panel for suspected previa with bleeding:

Anti-D immune globulin:

Transabdominal ultrasound (initial imaging):

Transvaginal ultrasound (gold standard):

Diagnostic thresholds at ≥32 weeks:

Step 3 management: If the 20-week anatomy scan shows a low-lying placenta or previa, rescan at 32 weeks (and again at 36 weeks if still abnormal) rather than committing to a delivery plan early — most resolve.

Board pearl: Transvaginal ultrasound is not contraindicated in previa — this is a frequently tested misconception. The probe enters only ~3 cm and stays angled away from the cervical canal.

Diagnostic Workup — Advanced and Confirmatory Studies

— Previa + prior cesarean is the highest-risk combination for accreta

— Risk of accreta with previa: ~3% with 0 prior cesareans, ~11% with 1, ~40% with 2, ~60% with 3, >65% with ≥4

— All patients with previa and prior cesarean should be screened for PAS

— Loss of the normal hypoechoic retroplacental clear zone

— Placental lacunae ("Swiss cheese" appearance, sometimes with turbulent Doppler flow)

— Bladder wall interruption or bulging

— Increased vascularity at the uteroplacental interface on color Doppler

— Myometrial thinning <1 mm

— Adjunct when ultrasound is equivocal or to evaluate posterior placentation, parametrial invasion, or bladder/bowel involvement

— Key findings: dark intraplacental T2 bands, uterine bulging, focal interruption of the myometrium

— Does not replace ultrasound but refines surgical planning

— Short cervix (<25–30 mm) in previa predicts antepartum hemorrhage and preterm delivery

— Used to time admission and antenatal corticosteroids

— Serial growth ultrasounds every 3–4 weeks — previa increases risk of FGR

— Nonstress test or biophysical profile if bleeding episodes or growth restriction

— Umbilical artery Doppler if FGR detected

— Repeat type and crossmatch close to scheduled delivery

— Confirm fibrinogen and platelets

— Multidisciplinary planning conference for suspected accreta: MFM, gynecologic oncology or surgeon experienced in cesarean hysterectomy, urology, anesthesia, interventional radiology, blood bank, neonatology

Evaluation for placenta accreta spectrum (PAS):

Ultrasound features of accreta spectrum:

MRI for accreta:

Cervical length measurement:

Fetal assessments:

Pre-delivery planning labs:

Key distinction: Placenta previa is a location diagnosis; placenta accreta spectrum is an invasion diagnosis. They commonly coexist but are separately evaluated, and accreta dramatically changes surgical risk, requiring delivery at a Level III/IV center with massive transfusion capability.

Board pearl: A pregnant woman with previa and ≥2 prior cesareans should be assumed to have accreta until proven otherwise.

Risk Stratification and First-Line Management Logic

— Asymptomatic previa, no prior bleeding: outpatient management is acceptable with strict precautions and reliable access to care

— Any antepartum bleeding episode: admit for observation, typically until bleeding stops for 48 hours; some centers admit until delivery after a sentinel bleed at ≥34 weeks

— Persistent or recurrent bleeding, short cervix, or distance from hospital → prolonged inpatient management

— Pelvic rest: no intercourse, no tampons, no digital exams

— Avoid strenuous exercise and heavy lifting

— Strict bed rest is not evidence-based and is discouraged due to VTE risk

— Have someone available to drive to the hospital; review warning signs

— Betamethasone 12 mg IM q24h × 2 doses (or dexamethasone 6 mg IM q12h × 4)

— Indicated at 24 0/7 to 33 6/7 weeks for any episode of bleeding or anticipated delivery within 7 days

— Late preterm course (34 0/7 to 36 6/7 weeks) acceptable if not previously given and delivery anticipated within 7 days

— Give if delivery anticipated before 32 weeks

— Reduces cerebral palsy risk in surviving preterm infants

— Controversial; may be considered for 48 hours to complete steroid course in stable patients with bleeding and contractions

— Avoid in unstable bleeding, nonreassuring fetal status, or abruption

Outpatient versus inpatient management:

Activity and lifestyle counseling:

Antenatal corticosteroids:

Magnesium sulfate for neuroprotection:

Tocolysis:

Anti-D prophylaxis: Standard 28-week dose plus additional dosing with each bleeding episode in Rh-negative patients

Step 3 management: Scheduled cesarean for uncomplicated previa is planned at 36 0/7 to 37 6/7 weeks; for suspected accreta, 34 0/7 to 35 6/7 weeks, both without amniocentesis for lung maturity (current ACOG practice).

Board pearl: Vaginal delivery is contraindicated in placenta previa — the planned route is always cesarean. Trial of labor is acceptable only when the placental edge is >20 mm from the os.

Pharmacotherapy and Supportive Medical Management

— Crystalloid: lactated Ringer's or normal saline as initial volume; avoid massive crystalloid (>2 L) before blood products

— PRBCs: transfuse for Hgb <7, or symptomatic anemia, or ongoing brisk bleeding

— Massive transfusion protocol: 1:1:1 ratio of PRBCs:FFP:platelets when ≥4 units anticipated

— Cryoprecipitate or fibrinogen concentrate: if fibrinogen <200 mg/dL

— Tranexamic acid (TXA) 1 g IV within 3 hours of postpartum hemorrhage onset reduces mortality (WOMAN trial); increasingly used antepartum as well

— Betamethasone 12 mg IM, two doses 24 hours apart is the preferred regimen

— Maximal benefit 24 hours to 7 days after the first dose; some benefit even before 24 hours

— A single rescue course may be given if >14 days since the initial course, gestation <34 weeks, and delivery anticipated within 7 days

— 4–6 g IV loading dose over 20–30 minutes, then 1–2 g/hr infusion

— Monitor deep tendon reflexes, respirations, urine output

— Antidote: calcium gluconate 1 g IV for toxicity

— Nifedipine (calcium channel blocker) — first-line; oral

— Indomethacin — only <32 weeks, short courses

— Avoid beta-agonists (terbutaline) for prolonged use due to maternal cardiac risk

— Magnesium sulfate may serve dual role (neuroprotection + mild tocolysis)

— Oral iron for mild antepartum anemia

— IV iron (ferric carboxymaltose, iron sucrose) for moderate-severe anemia, intolerance to oral iron, or limited time before delivery

— Pneumatic compression for hospitalized antepartum patients

— Pharmacologic prophylaxis individualized; held around delivery and procedures

Hemorrhage resuscitation pharmacology:

Antenatal corticosteroids — specifics:

Magnesium sulfate for neuroprotection:

Tocolytic options when used:

Iron repletion:

VTE prophylaxis:

CCS pearl: On a CCS case with previa bleeding at 30 weeks, your order set should include: admit L&D, NPO, continuous fetal monitoring, IV access ×2, type and crossmatch, betamethasone, magnesium sulfate for neuroprotection, Rh status check with RhoGAM if needed, and serial CBC.

Procedures, Surgical Delivery, and Invasive Management

— Scheduled at 36 0/7 to 37 6/7 weeks without amniocentesis

— Performed in a hospital with blood bank, anesthesia, and NICU capability

— Neuraxial anesthesia preferred unless hemodynamically unstable or accreta with anticipated long, bloody case (then general)

— Consider vertical or fundal hysterotomy if an anterior previa makes the lower segment vascular and a low transverse incision would transect the placenta

— Deliver at a Level III/IV center between 34 0/7 and 35 6/7 weeks after steroids

— Cesarean hysterectomy is the standard of care: do not attempt to remove the placenta; leave it in situ, close the hysterotomy, and proceed to hysterectomy

— Pre-operative ureteral stents to reduce ureteral injury

— Preoperative cell saver and massive transfusion protocol activated

— Optional prophylactic balloon catheters in internal iliac or uterine arteries by interventional radiology — variable evidence

— Conservative management (placenta left in situ + methotrexate or expectant resorption) is investigational and reserved for select patients

— Uterotonics: oxytocin first-line; add methylergonovine (avoid in HTN), carboprost (avoid in asthma), misoprostol

— Bimanual uterine massage

— B-Lynch suture for atony

— Uterine artery ligation or internal iliac (hypogastric) artery ligation

— Intrauterine balloon tamponade (Bakri balloon)

— Uterine artery embolization by IR if patient stabilizable

— Hysterectomy as definitive control when conservative measures fail

— Active heavy bleeding with maternal instability

— Nonreassuring fetal status

— Labor with previa at viable gestation

Planned cesarean delivery — uncomplicated previa:

Suspected accreta spectrum — surgical principles:

Intraoperative hemorrhage control after delivery:

Emergency cesarean indications:

Board pearl: In accreta, do not attempt to manually remove the placenta — this is the single most common cause of catastrophic intraoperative hemorrhage. Anticipate hysterectomy and have ≥4 units PRBCs in the room before incision.

Step 3 management: A patient at 35 weeks with previa, prior cesarean, and ultrasound showing placental lacunae and loss of the retroplacental clear zone should be transferred to a tertiary center for planned cesarean hysterectomy.

Special Populations — Comorbidity Considerations

— Preeclampsia increases risk of concomitant abruption — a critical differential when these patients bleed

— Avoid methylergonovine (ergot) for postpartum hemorrhage in hypertensive patients — can precipitate stroke or severe hypertension

— Magnesium sulfate doses overlap (neuroprotection and seizure prophylaxis); careful monitoring for toxicity

— BP goals: <160/110 acutely (labetalol, hydralazine, oral nifedipine)

— Steroid administration causes hyperglycemia; anticipate with insulin scale or drip

— Frequent glucose checks q2–4h during and 24 hours after betamethasone course

— Macrosomia may compound difficulty if previa with malpresentation

— Optimize hemoglobin antepartum with iron (oral or IV); goal Hgb >11 g/dL before delivery if possible

— Consider erythropoietin in select cases of severe iron-refractory anemia

— Inherited bleeding disorders (vWD, hemophilia carriers): hematology involvement, factor levels checked

— Therapeutic anticoagulation must be transitioned around delivery: LMWH stopped 24 hours pre-op; unfractionated heparin 4–6 hours

— Reversal: protamine for heparin, PCC for warfarin (rare in pregnancy)

— Adjust magnesium sulfate (renally cleared) — reduce maintenance dose and monitor levels and reflexes closely

— Adjust LMWH dosing if used for VTE prophylaxis

— Coexisting thrombocytopenia compounds hemorrhage risk

— Platelet transfusion threshold for cesarean: ≥50,000/μL; for neuraxial anesthesia: typically ≥70,000–80,000/μL

— Advance discussion of acceptable blood products

— Use cell saver, TXA, iron optimization, erythropoietin, and minimize blood draws

— Consider transfer to a center with bloodless medicine expertise

Patients with chronic hypertension or preeclampsia:

Patients with diabetes (pregestational or gestational):

Patients with anemia at baseline:

Patients with coagulopathy or on anticoagulation:

Renal impairment:

Hepatic impairment / HELLP overlap:

Jehovah's Witness patients:

Board pearl: The combination of previa, hypertension, and prior cesarean places a patient in the highest tier of obstetric morbidity — manage them at a tertiary center with multidisciplinary preoperative planning.

Special Populations — Demographic Subgroups

— Independent risk factor for previa, accreta, and operative morbidity

— Higher comorbidity burden (chronic HTN, DM); counsel about cumulative risks of multiple cesareans for accreta

— Each additional cesarean compounds previa and accreta risk

— Discuss permanent contraception (tubal ligation at cesarean or postpartum) when family complete — informed consent must be obtained well in advance, not in active labor

— ART roughly doubles previa risk independent of maternal age

— Counsel during early pregnancy and ensure timely anatomy scan

— Larger placental surface area increases previa risk

— Higher baseline preterm delivery risk; coordinate steroid timing carefully

— Lower baseline previa risk but social vulnerability — address transportation, support, and ensure understanding of pelvic rest precautions

— Confidentiality and consent: minor pregnant patients are generally treated as emancipated for pregnancy-related care in the US, but state laws vary

— Use professional medical interpreters (not family) for consent and discharge instructions

— Teach-back method to confirm understanding of bleeding precautions

— Written instructions in primary language

— Patients with previa should deliver at a center with cesarean, anesthesia, and blood bank capability

— Antepartum transfer to a tertiary center is far safer than emergency intrapartum transfer

— Consider scheduled relocation closer to delivery if travel distance is significant

— Cocaine and tobacco use raise previa and abruption risk

— Non-judgmental screening (SBIRT); offer cessation counseling, NRT, buprenorphine for OUD

— Coordinate with social work; do not let stigma delay imaging or transfusion

Advanced maternal age (≥35):

Multiparas with prior cesareans:

In vitro fertilization (IVF) pregnancies:

Multifetal gestations:

Adolescents:

Patients with limited English proficiency or low health literacy:

Rural and resource-limited settings:

Patients with substance use disorder:

Step 3 management: A G4P3 at 34 weeks with previa, three prior cesareans, and ultrasound features of accreta should be transferred to a Level IV center, given betamethasone, scheduled for cesarean hysterectomy at 34–35 weeks, and counseled in advance about hysterectomy, transfusion, and future fertility loss.

Complications and Adverse Outcomes

— Antepartum hemorrhage requiring transfusion in up to 25% of symptomatic cases

— Intrapartum and postpartum hemorrhage rates also elevated — the lower uterine segment contracts poorly after placental delivery

— Hemorrhagic shock, DIC, acute tubular necrosis, Sheehan syndrome (postpartum pituitary necrosis), and death

— Accreta, increta, percreta — strongly associated with previa over prior cesarean scar

— May require cesarean hysterectomy, with bladder or bowel injury, ureteral injury, fistula formation

— Average blood loss in accreta cesarean hysterectomy: 2–5 L; massive transfusion frequently required

— ~40–50% of symptomatic previas deliver before 37 weeks

— Neonatal complications: RDS, IVH, NEC, retinopathy of prematurity — mitigated by antenatal steroids and magnesium

— Modest increase, especially with recurrent bleeding episodes

— High incidence of transverse and breech lie

— Cord prolapse risk if membranes rupture with a low-lying placenta

— Bladder, ureter, or bowel injury, particularly in accreta cases

— Anesthetic complications, postoperative ileus, infection, wound complications

— Venous thromboembolism in the postpartum period

— Fetal vessels traversing the membranes over the cervix can rupture with ROM → fetal exsanguination

— Screen with transvaginal color Doppler in patients with low-lying placenta, succenturiate lobes, or velamentous cord insertion

— Prolonged hospitalization, fear of bleeding, NICU separation, and unplanned hysterectomy contribute to anxiety, depression, and PTSD

— Screen postpartum and refer

— Largely driven by gestational age at delivery

— Anemia is rare in the neonate (bleeding is maternal, not fetal) — distinguishes previa from vasa previa

Maternal hemorrhage:

Placenta accreta spectrum:

Preterm delivery:

Fetal growth restriction:

Malpresentation and cord prolapse:

Operative morbidity:

Vasa previa coexistence:

Psychological morbidity:

Neonatal outcomes:

Board pearl: The bleeding in placenta previa is maternal blood; the bleeding in vasa previa is fetal blood — this distinction drives the management urgency and the neonatal resuscitation plan.

When to Escalate Care — ICU, Consults, and Inpatient Triage

— Any third-trimester vaginal bleeding

— Decreased fetal movement, contractions, or rupture of membranes

— Hemodynamic instability or signs of shock

— Hemorrhagic shock requiring vasopressors or massive transfusion (>4 units PRBCs/24 h)

— DIC with active bleeding

— Postoperative instability after cesarean hysterectomy

— Acute kidney injury, ARDS, or transfusion-related lung injury

— Maternal-Fetal Medicine for any previa at <36 weeks, suspected accreta, or recurrent bleeding

— Anesthesia early — preoperative consult to plan neuraxial vs general, large-bore access, arterial line

— Blood bank — ensure crossmatched units available; activate massive transfusion protocol early

— Gynecologic oncology or experienced pelvic surgeon for suspected accreta

— Urology for placenta percreta with bladder involvement

— Interventional radiology for prophylactic balloons or postpartum embolization

— Neonatology for preterm or accreta deliveries

— Social work for prolonged hospitalization and discharge planning

— Suspected accreta spectrum

— Hospital lacks 24-hour cesarean, blood bank, anesthesia, or NICU

— Anticipated delivery before 32 weeks

— Coexisting maternal comorbidities exceeding local capability

— Persistent severe maternal hemorrhage unresponsive to resuscitation

— Nonreassuring fetal status despite intrauterine resuscitation

— Labor that cannot be safely tocolyzed in active previa bleeding

— Any abruption complicating previa

— Coexisting preeclampsia with severe features at ≥34 weeks

Indications for immediate L&D admission:

Indications for ICU-level care:

Consultations:

Antepartum transfer criteria (to higher-level center):

When to deliver despite prematurity:

CCS pearl: On a CCS case, if maternal vitals deteriorate (HR >120, SBP <90) despite 2 L crystalloid and 2 units PRBCs in a bleeding previa patient, your next moves are activate MTP, call OR, page anesthesia and OB, deliver by cesarean — do not continue to temporize.

Board pearl: Escalation in obstetric hemorrhage is a time-critical, team-based action — early activation of the massive transfusion protocol saves lives more reliably than any single drug.

Key Differentials — Same-Category Causes (Other Antepartum Hemorrhage)

— Premature separation of a normally implanted placenta

— Painful, often dark vaginal bleeding (may be concealed)

— Rigid, tender, "woody" uterus, frequent contractions, possibly hyperstimulation pattern

— Risk factors: hypertension, preeclampsia, trauma, cocaine, tobacco, prior abruption, PPROM, polyhydramnios after ROM

— Ultrasound has poor sensitivity (~25–50%); diagnosis is largely clinical

— Complications: DIC (highest of any OB cause), fetal demise, Couvelaire uterus

— Fetal vessels crossing the internal os, unsupported by placenta or cord (velamentous insertion or succenturiate lobe)

— Painless bleeding with rupture of membranes + acute fetal distress (sinusoidal tracing or bradycardia)

— Diagnosed antenatally by transvaginal color Doppler

— Management: scheduled cesarean at 34–36 weeks with antenatal steroids

— Sudden severe pain, loss of fetal station, fetal bradycardia, hemodynamic collapse

— Strong association with prior cesarean during TOLAC, especially with classical incision

— Bleeding may be vaginal, intra-abdominal, or both

— Emergent laparotomy

— Small amount of bloody mucus discharge with cervical effacement near term

— No hemodynamic concern; normal labor finding

— Cervicitis, cervical polyps, postcoital bleeding from friable cervix, cervical cancer

— Identified on speculum exam after previa is excluded

— More common in first/early second trimester; usually self-limited

— Ultrasound shows crescent-shaped hypoechoic area adjacent to gestational sac

— Previa: painless, bright red, soft uterus, normal FHR

— Abruption: painful, dark, tender rigid uterus, fetal distress, DIC risk

— Vasa previa: painless after ROM, bright red, fetal distress, fetal blood

— Rupture: sudden pain, loss of station, prior uterine scar

Placental abruption (abruptio placentae):

Vasa previa:

Uterine rupture:

Bloody show / cervical change:

Cervical or vaginal pathology:

Subchorionic hematoma:

Key distinction table for the exam:

Board pearl: When the stem mentions fetal heart rate abnormality + bleeding + recent rupture of membranes, think vasa previa first — it is the only one where the bleeding is fetal and minutes matter for fetal survival.

Key Differentials — Other-Category Causes

— Cervicitis (gonorrhea, chlamydia, trichomonas) — friable cervix bleeds on contact

— Cervical polyps — benign, may bleed spontaneously or postcoitally

— Cervical ectropion — common in pregnancy due to estrogen

— Cervical cancer — do not miss; obtain Pap if not up to date and biopsy any suspicious lesion (acceptable in pregnancy)

— Vaginitis (BV, candida, trichomonas)

— Lacerations from intercourse or trauma

— Varicosities

— Hematuria from UTI, stones, or rarely bladder pathology may be mistaken for vaginal bleeding

— Urinalysis distinguishes

— Hemorrhoids (very common in pregnancy), anal fissures

— Rarely upper or lower GI sources mistaken for vaginal bleeding by patients

— Von Willebrand disease, ITP, inherited platelet disorders

— Pregnancy-related: HELLP syndrome, acute fatty liver of pregnancy, sepsis-related DIC

— Anticoagulant use

— Motor vehicle collision, intimate partner violence (screen privately and routinely)

— Always evaluate for occult abruption with Kleihauer-Betke and prolonged monitoring (≥4 hours) after significant trauma

— Fever, foul discharge, uterine tenderness, leukocytosis

— Antibiotics + delivery

— "Snowstorm" on ultrasound, markedly elevated β-hCG, hyperemesis, theca lutein cysts

— Treat with suction D&C and follow β-hCG to zero

— Not a differential in the third trimester, but classic for early bleeding

— Adnexal mass, no intrauterine pregnancy, β-hCG above discriminatory zone

Non-obstetric sources of vaginal bleeding in pregnancy:

Cervical causes:

Vaginal and vulvar causes:

Urinary tract bleeding:

Gastrointestinal bleeding:

Coagulation disorders:

Trauma:

Infectious chorioamnionitis or septic miscarriage:

Molar pregnancy (typically first trimester):

Ectopic pregnancy (first trimester):

Step 3 management: Always perform a sterile speculum exam after previa is excluded by ultrasound — many "previa" cases on the exam turn out to be cervicitis, polyps, or trauma identified by careful inspection. Screen all pregnant patients for IPV at least once per trimester.

Board pearl: Pregnancy does not protect against cancer — a friable, irregular cervical lesion in a bleeding pregnant patient warrants biopsy, not reassurance.

Secondary Prevention and Long-Term Plan

— Recurrence risk of previa: 4–8% in subsequent pregnancies

— Risk of accreta rises sharply with each cesarean — discuss optimal family size and interval

— Optimal interpregnancy interval: at least 6 months, ideally 18–24 months after cesarean

— Consider permanent contraception (tubal ligation, bilateral salpingectomy at cesarean, vasectomy) if family is complete and patient desires, especially after accreta hysterectomy is anticipated

— Initiate contraception before discharge to prevent short-interval pregnancy

— Immediate postpartum IUD or implant; progestin-only methods compatible with breastfeeding

— Avoid estrogen-containing methods in the first 21–42 days postpartum due to VTE risk (longer for higher-risk patients)

— Smoking cessation — counseling, NRT, varenicline (after weighing risks); reduces previa, abruption, and IUGR risk in future pregnancies

— Address cocaine and other substance use with referral to addiction treatment

— Optimize chronic conditions (HTN, DM) preconceptionally

— Continue oral or IV iron for 3 months postpartum to replenish stores after antepartum or postpartum hemorrhage

— Recheck Hgb at 6 weeks

— Mechanical and/or pharmacologic prophylaxis individualized; prolonged LMWH up to 6 weeks postpartum for highest-risk patients (cesarean + obesity + immobility, prior VTE)

— Screen for postpartum depression and PTSD at 1–2 weeks and 6 weeks postpartum

— Refer to therapy and pharmacotherapy as needed

— Final postpartum dose to Rh-negative mothers with Rh-positive infants within 72 hours of delivery

Future pregnancy counseling:

Contraception postpartum:

Modifiable risk reduction:

Iron repletion:

VTE prophylaxis postpartum:

Mental health follow-up:

Anti-D Ig:

Step 3 management: At the comprehensive postpartum visit (4–6 weeks), address contraception, smoking cessation, mood screening, iron status, and future pregnancy planning — particularly counseling about accreta risk if additional cesareans are anticipated.

Board pearl: A woman after accreta-associated cesarean hysterectomy is a candidate for trauma-informed mental health follow-up, not just routine postpartum care — unplanned loss of fertility is a major emotional event.

Follow-Up, Monitoring, and Counseling

— Anatomy ultrasound at 18–22 weeks documents placental location

— Repeat transvaginal ultrasound at 32 weeks if previa or low-lying placenta persists

— Repeat at 36 weeks if still abnormal to finalize delivery route

— Serial growth ultrasounds every 3–4 weeks for documented previa

— Antenatal testing (NST, BPP) weekly from 32–34 weeks for symptomatic or growth-restricted cases

— Any vaginal bleeding, even a small amount → go to L&D immediately

— Contractions, leakage of fluid, decreased fetal movement

— Severe abdominal pain

— Lightheadedness, syncope

— Have a transport plan in place and carry a card stating "placenta previa — no digital cervical exam"

— Vital signs q4h or more frequently

— Daily CBC during active bleeding; trend hemoglobin and platelets

— Intermittent or continuous fetal monitoring per protocol

— Maintain active type and crossmatch (refresh every 72 hours)

— DVT prophylaxis with pneumatic compression devices

— Cesarean delivery, including risks of hemorrhage, transfusion, infection, injury to bladder/bowel/ureters

— Possibility of hysterectomy if hemorrhage uncontrollable or accreta confirmed intraoperatively

— Need for blood products; discuss directed donation or refusal in advance

— Risk of preterm delivery and NICU admission

— Postoperative recovery expectations

— Inpatient: monitor for delayed postpartum hemorrhage, hemoglobin trend, wound check

— 1–2 week postpartum visit (especially after complicated delivery)

— Comprehensive 4–6 week visit

— Mental health screening at each touchpoint

— Encourage breastfeeding; not contraindicated by previa or cesarean

— Hemorrhage and iron deficiency can delay lactogenesis II — provide lactation support proactively

Antepartum surveillance schedule:

Outpatient warning signs — patient education:

Inpatient monitoring (during admission for bleeding):

Pre-delivery counseling — informed consent items:

Postpartum follow-up cadence:

Lactation:

Board pearl: Patient education and a written emergency plan are interventions in their own right — they are tested as the "best next step" when a stable outpatient with previa is being discharged.

CCS pearl: Order "discharge instructions: pelvic rest, no intercourse, return for any bleeding, contractions, ROM, or decreased fetal movement" as a discrete CCS step.

Ethical, Legal, and Patient Safety Considerations

— Obtain consent for cesarean and for possible hysterectomy in advance when accreta is suspected — not in the middle of intraoperative hemorrhage

— Use teach-back to confirm understanding of risks (transfusion, loss of fertility, ICU, death)

— Document discussion thoroughly; involve interpreters when needed

— A patient retains the right to refuse cesarean even when fetal life is at risk; explore reasons, address fears, and offer ethics consult

— Discuss acceptable products (cell saver, albumin, recombinant factors, fractionated products) in advance and document

— Respect competent adult refusal even if life-threatening

— Court orders to compel transfusion in pregnant patients are legally fraught and ethically discouraged in the US current framework

— The competent pregnant patient is the decision-maker; the fetus is not a separate patient with legally enforceable rights

— Coercion or court-ordered cesarean is rarely upheld and discouraged by ACOG

— Suspected intimate partner violence: offer resources but reporting requirements vary by state (most do not mandate physician reporting of IPV in competent adults; do report injuries from weapons, child abuse, elder abuse)

— Positive drug screens in pregnancy: state-dependent reporting laws; counsel about implications, provide non-punitive treatment

— Antepartum transfer to a tertiary center: ensure direct provider-to-provider handoff, transfer of imaging, type and crossmatch sample, anti-D documentation

— Shift change in L&D: structured handoff (SBAR) with explicit mention of previa status, prior bleeding, MTP readiness

— Discharge after stabilization: confirm transportation, contact phone, follow-up appointment booked, warning signs reviewed

— Unanticipated outcomes (hysterectomy, ICU admission, neonatal injury) require honest, prompt disclosure with the patient and family

— Document the disclosure conversation; involve risk management early when serious harm occurs

— Black women face 3–4× higher maternal mortality from obstetric hemorrhage; systematic bias in pain assessment and time-to-intervention contributes — address with standardized protocols and team training

Informed consent for cesarean and hysterectomy:

Jehovah's Witnesses and blood product refusal:

Maternal-fetal conflict:

Mandatory reporting:

Transitions of care — patient safety risks:

Disclosure of complications:

Health equity:

Board pearl: A pregnant patient who refuses cesarean for previa with active bleeding cannot be operated on against her will; the correct answer involves continued counseling, ethics consult, and respect for autonomy, not court order.

High-Yield Associations and Rapid-Fire Clinical Facts

— Painless, bright red, third-trimester bleeding = placenta previa until proven otherwise

— Prior cesarean + anterior previa = accreta spectrum until proven otherwise

— Painless bleeding + ROM + fetal bradycardia = vasa previa

— Painful dark bleeding + tender rigid uterus = abruption

— Sudden pain + loss of fetal station + prior uterine surgery = uterine rupture

— Cesarean delivery timing for uncomplicated previa: 36 0/7 – 37 6/7 weeks

— Cesarean delivery timing for accreta: 34 0/7 – 35 6/7 weeks

— Distance from os defining previa vs low-lying: 2 cm (20 mm)

— Trial of labor acceptable: placental edge >20 mm from os

— Anti-D dose: 300 mcg IM for routine bleeding episodes in Rh-negative

— Betamethasone: 12 mg IM × 2 doses, 24 hours apart

— Magnesium neuroprotection cutoff: <32 weeks

— TXA dose for PPH: 1 g IV within 3 hours

— Massive transfusion ratio: 1:1:1 (PRBCs:FFP:platelets)

— Recurrence risk of previa: 4–8%

— Accreta risk with previa and ≥3 prior cesareans: >60%

— Transvaginal ultrasound is SAFE in previa — frequently tested misconception

— Empty bladder when performing transabdominal scan to avoid false previa

— "Swiss cheese" placental lacunae on ultrasound → think accreta

— MRI is adjunct, not replacement, for accreta evaluation

— Avoid methylergonovine for postpartum hemorrhage in patients with hypertension or preeclampsia

— Avoid carboprost in asthma

— Avoid digital cervical exam until previa is excluded

— Risk factors: prior cesarean, prior previa, multiparity, AMA, smoking, cocaine, ART, multiples

— "Previa is painless, pristine, and posterior to the os" — painless bleed, no tenderness, placenta over or near the os

— Third-trimester bleeding → admit, IV ×2, type & cross, ultrasound, fetal monitoring, no digital exam

— Heavy bleeding + instability → activate MTP, OR for emergent cesarean

Quick associations:

Key numbers:

Imaging pearls:

Pharmacology pitfalls:

Etiologic mnemonics:

CCS triggers:

Board pearl: If the question stem mentions a patient with prior multiple cesareans and current previa, the test is asking about accreta spectrum — answer with multidisciplinary planning, scheduled preterm cesarean hysterectomy, and tertiary care center delivery.

Board Question Stem Patterns

— "A 32-year-old G3P2 at 30 weeks calls reporting sudden onset of painless bright red vaginal bleeding that has now stopped. She has had two prior cesareans."

— Correct answer: Send to L&D for evaluation, transabdominal then transvaginal ultrasound, type and crossmatch, fetal monitoring — not in-office speculum, not reassurance.

— "Transabdominal ultrasound is equivocal for placental location. What is the next step?"

— Correct answer: Transvaginal ultrasound (most commonly missed answer because of the misconception that it is contraindicated).

— "Asymptomatic placenta previa confirmed at 36 weeks. When should delivery be scheduled?"

— Correct answer: Cesarean at 36 0/7 to 37 6/7 weeks without amniocentesis.

— "G5P4 at 33 weeks with placenta previa, three prior cesareans, ultrasound shows placental lacunae and loss of the retroplacental clear zone."

— Correct answer: Plan cesarean hysterectomy at 34–35 weeks at a tertiary center after antenatal corticosteroids; multidisciplinary preoperative planning.

— "Painful dark vaginal bleeding with a rigid tender uterus and Category III fetal tracing at 34 weeks in a patient with chronic HTN."

— Correct answer: Placental abruption — emergent cesarean; assess for DIC.

— "Painless bright red bleeding immediately after spontaneous rupture of membranes, sinusoidal fetal heart rate tracing."

— Correct answer: Vasa previa — emergent cesarean; this is fetal blood.

— "After cesarean for previa, uterus is boggy, blood loss 1500 mL despite oxytocin, BP 140/95."

— Correct answer: Avoid methylergonovine (HTN); use carboprost (unless asthma), TXA, bimanual massage, Bakri balloon, escalate to B-Lynch or hysterectomy.

— "Placenta previa with bleeding at 33 weeks, stable, no contractions."

— Correct answer: Betamethasone, admit, observe, magnesium for neuroprotection if delivery imminent.

— Jehovah's Witness with previa and accreta refuses transfusion.

— Correct answer: Respect autonomy, optimize iron, cell saver, multidisciplinary planning, document advance directive.

Stem pattern 1 — Classic outpatient call:

Stem pattern 2 — Diagnostic next step:

Stem pattern 3 — Timing of delivery:

Stem pattern 4 — Accreta recognition:

Stem pattern 5 — Differentiating from abruption:

Stem pattern 6 — Vasa previa pitfall:

Stem pattern 7 — Postpartum hemorrhage management:

Stem pattern 8 — Steroid timing:

Stem pattern 9 — Ethics/consent:

Board pearl: Step 3 favors the management-cascade stem — the right answer is rarely "diagnose"; it is "the next order you would place" or "the next location of care."

One-Line Recap

Placenta previa is painless bright red third-trimester bleeding caused by placental implantation over or within 2 cm of the internal cervical os, diagnosed by transvaginal ultrasound (which is safe), managed with pelvic rest, antenatal corticosteroids if <34 weeks, and scheduled cesarean delivery at 36 0/7–37 6/7 weeks (or 34 0/7–35 6/7 weeks with suspected accreta), and digital cervical exam is contraindicated until previa is excluded.

— Suspect with painless bright red bleeding in the second half of pregnancy or routine anatomy scan finding

— Confirm with transvaginal ultrasound — safe and gold standard

— Always evaluate for accreta spectrum in patients with previa and prior cesarean (ultrasound first, MRI adjunct)

— No digital exam until previa excluded

— Outpatient with pelvic rest if asymptomatic and reliable; admit for any bleeding episode

— Betamethasone at 24–34 weeks; magnesium for neuroprotection if <32 weeks

— RhoGAM for Rh-negative patients with any bleeding

— Scheduled cesarean 36 0/7–37 6/7 weeks (uncomplicated previa); 34 0/7–35 6/7 weeks (suspected accreta)

— Tertiary center, multidisciplinary team, blood bank readiness for accreta

— Abruption — painful, dark, tender uterus, DIC risk

— Vasa previa — painless bleed after ROM with fetal bradycardia (fetal blood)

— Uterine rupture — sudden pain, loss of fetal station, prior cesarean

— Recurrence risk 4–8%; counsel on family planning, smoking cessation, and accreta risk with future cesareans

— Postpartum: iron repletion, VTE prophylaxis, contraception, mental health screening, comprehensive 4–6 week visit

Diagnosis recap:

Management recap:

Differentials recap:

Long-term recap:

Board pearl: The single highest-yield teaching point — transvaginal ultrasound is safe in suspected placenta previa, and digital cervical exam is forbidden until previa has been excluded.