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Trusted, evidence-based resources for women navigating placenta previa, placenta accreta spectrum, and related maternal complications. Know your options, understand your risks, and connect with specialists.
Understanding monitoring, activity restrictions, and delivery planning with your care team.
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Learn about the two primary placental complications, their symptoms, diagnosis methods, and management strategies recommended by maternal-fetal medicine specialists.
A condition where the placenta partially or completely covers the cervical opening (os). This can cause painless vaginal bleeding, particularly in the third trimester, and typically requires cesarean delivery.
A group of conditions (accreta, increta, percreta) where the placenta abnormally attaches too deeply into the uterine wall. Often associated with prior C-sections, it carries a higher risk of major hemorrhage.
Placenta previa often has no symptoms early on, but key warning signs include:
Painless vaginal bleeding — especially in 2nd or 3rd trimester
Bright red bleeding — can begin suddenly without warning
Uterine cramping — especially after bleeding episodes
Breech or transverse position — baby may not be head-down
Recurring bleeding — episodes may stop and restart
Large uterus for gestational age — less common indicator
Note: Some women have no bleeding at all. Previa is often diagnosed via routine ultrasound.
Placenta previa is diagnosed using imaging. The standard diagnostic pathway involves:
Transvaginal ultrasound — most accurate method for placental localization
Transabdominal ultrasound — often used first; may miss low-lying placenta
MRI — used when ultrasound is inconclusive or accreta is suspected
Follow-up scans at 32–36 weeks — ~90% of low-lying placentas resolve by term
Management depends on gestational age, symptoms, and degree of previa:
Pelvic rest — no intercourse, tampons, or pelvic exams
Activity restriction — reduced physical exertion; sometimes bed rest
Regular monitoring — ultrasound every 2–4 weeks in 3rd trimester
Corticosteroids — if preterm delivery is anticipated to mature fetal lungs
Hospitalization — for heavy bleeding or if far from medical care
Planned cesarean — typically at 36–37 weeks; earlier if bleeding persists
Placenta accreta spectrum (PAS) is often asymptomatic during pregnancy. Risk factors and signs include:
Prior cesarean delivery — #1 risk factor; risk increases with each C-section
Prior uterine surgery — myomectomy, D&C, endometrial ablation, or any procedure that scars the uterine wall
Low-lying or previa placenta — PAS very common when previa overlies a uterine scar
IVF / frozen embryo transfer — research shows significantly elevated PAS risk, especially with hormone replacement cycles
Abnormal 3rd trimester bleeding — may indicate partial abruption
Difficulty with placental delivery — often first recognized at time of birth
Elevated AFP — abnormal maternal serum screening result may prompt further workup
PAS is often not detected until delivery. When suspected, diagnosis involves:
Transvaginal ultrasound — first-line imaging; looks for loss of clear zone, lacunae (irregular vascular spaces), and abnormal placental blood flow
Color Doppler ultrasound — identifies abnormal vascularity and uterine wall invasion
MRI — used when ultrasound is inconclusive; helps assess depth of invasion and involvement of bladder or surrounding organs
Elevated maternal AFP — abnormal second-trimester serum screening may prompt further imaging workup
History review — prior C-sections, uterine surgeries, IVF, and placenta location are key diagnostic factors
Referral to MFM specialist — formal diagnosis and delivery planning should involve a maternal-fetal medicine specialist at a PAS center
Note: PAS in IVF patients is significantly less likely to be detected prenatally — proactive screening is essential even without classic risk factors.
PAS requires a highly specialized, multidisciplinary approach. Management typically involves:
Delivery at a PAS Center of Excellence — hospitals with dedicated multidisciplinary teams
MFM + surgical specialists — OB, urology, vascular surgery, and interventional radiology
Cell salvage and transfusion readiness — large blood loss is expected
Planned hysterectomy — typically recommended to prevent life-threatening hemorrhage
Delivery at 34–36 weeks — planned preterm birth reduces emergency risk
Counseling on fertility — hysterectomy ends future pregnancies; discussion is essential
The placenta accreta spectrum describes three grades of abnormal placental attachment, defined by how deeply the placenta invades the uterine wall:
Attaches too firmly to the uterine wall but does not penetrate the muscle. The normal separating tissue (decidua) is absent.
Invades into the myometrium (uterine muscle). Separation at delivery is extremely difficult and hemorrhage risk is significantly elevated.
The most severe form — penetrates entirely through the uterine wall and may invade surrounding organs such as the bladder or bowel.
Note: All three types require delivery at a PAS Center of Excellence. Depth of invasion determines surgical complexity and blood loss risk.
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