Glossary & Resources

Medical Terms Glossary

Medical terminology can feel overwhelming. This glossary provides clear, patient-friendly definitions for terms you may encounter when learning about Placenta Accreta Spectrum. Use the search box or letter links to find a specific term quickly.

ACOG(ay-cog)

American College of Obstetricians and Gynecologists. The leading professional organization for OB-GYN physicians in the United States. ACOG publishes clinical guidelines that shape how PAS is diagnosed and managed. PAS context: ACOG guidelines recommend delivery at 34–36 weeks for confirmed PAS with a multidisciplinary team.

Adhesion

Bands of scar-like tissue that form between organs or tissues that are not normally connected. They commonly develop after surgery, infection, or inflammation. PAS context: Prior cesarean sections create uterine scar tissue and adhesions, which can make subsequent surgeries more complex and increase the risk of abnormal placental attachment.

AFP (Alpha-fetoprotein)

A protein produced by a developing baby. Measured through a maternal blood test, AFP levels can be part of routine prenatal screening. PAS context: Elevated maternal AFP levels in the second trimester have been associated with PAS in some studies, though this is not a reliable standalone diagnostic test.

Amniotic fluid(am-nee-OT-ik)

The protective liquid that surrounds and cushions the baby inside the uterus throughout pregnancy. It helps regulate temperature, allows the baby to move, and supports lung development. PAS context: During ultrasound evaluation for PAS, the relationship between the placenta, amniotic fluid, and uterine wall is carefully assessed.

Anterior placenta

A placenta that is attached to the front wall of the uterus (the side closest to your belly). PAS context: An anterior placenta overlying a prior cesarean scar is the most common scenario for PAS. This location makes ultrasound diagnosis somewhat more straightforward compared to a posterior placenta.

Antepartum(an-tee-PAR-tum)

The period before birth or delivery. Often used to describe care, monitoring, or complications that occur during pregnancy before the baby arrives. PAS context: Antepartum diagnosis of PAS (detecting it before delivery) significantly improves outcomes compared to discovering it during delivery.

Arterial embolization(em-boh-lih-ZAY-shun)

A minimally invasive procedure in which a specialist (interventional radiologist) threads a small catheter through blood vessels and injects material to block a specific artery, reducing blood flow to a targeted area. PAS context: Uterine artery embolization may be used before, during, or after cesarean delivery to help control hemorrhage in PAS cases.

Bilateral(bye-LAT-er-ul)

Occurring on or affecting both sides. PAS context: Surgeons may perform bilateral uterine artery ligation (tying off arteries on both sides) to reduce blood loss during PAS surgery.

Biomarker

A measurable substance in the body (such as a protein in blood) that can indicate the presence or severity of a medical condition. PAS context: Researchers are actively working to identify reliable blood biomarkers that could help diagnose PAS earlier or predict its severity, though none are yet standard practice.

Bladder

A hollow, muscular organ in the pelvis that stores urine. It sits directly in front of the lower part of the uterus. PAS context: In severe PAS (percreta), the placenta can grow through the uterine wall and invade the bladder. This is why bladder involvement is carefully evaluated during imaging, and a urologist may be part of the surgical team.

Blood products

Components prepared from donated blood, including packed red blood cells, fresh frozen plasma, platelets, and cryoprecipitate. Each serves a different purpose in treating blood loss. PAS context: Significant blood loss is common in PAS deliveries. Specialized centers ensure large quantities of blood products are immediately available ("massive transfusion protocol"), which is a key reason to deliver at an experienced facility.

Cesarean section (C-section)(sih-ZAIR-ee-un)

A surgical procedure in which the baby is delivered through incisions made in the mother's abdomen and uterus, rather than through the vagina. PAS context: Prior cesarean delivery is the single greatest risk factor for PAS. The risk increases with each additional cesarean: from about 0.3% after one C-section to over 6% after five or more.

Cervix(SUR-viks)

The lower, narrow end of the uterus that opens into the vagina. It dilates during labor to allow the baby to pass through. PAS context: When the placenta covers the cervix (placenta previa), it often overlies a prior cesarean scar, creating conditions that favor PAS development.

Coagulopathy(koh-ag-yoo-LOP-uh-thee)

A condition in which the blood's ability to clot is impaired, leading to prolonged or excessive bleeding. PAS context: Massive hemorrhage during PAS surgery can lead to coagulopathy, which is why blood banks and hematologists are part of the PAS care team.

Color Doppler

An ultrasound technique that uses color to show the direction and speed of blood flowing through vessels. Blood flowing toward the probe is shown in one color and blood flowing away in another. PAS context: Color Doppler is essential for PAS diagnosis. It can reveal abnormal blood vessels crossing from the placenta into the uterine wall or bladder, a hallmark sign of PAS.

Conservative management

A treatment approach that aims to avoid or minimize surgery. In the context of PAS, this typically means leaving all or part of the placenta inside the uterus (in situ) rather than performing a hysterectomy. PAS context: Conservative management may be considered to preserve fertility but carries risks of delayed hemorrhage, infection, and need for additional procedures. It requires very close long-term follow-up.

Decidua / Decidua basalis(deh-SID-yoo-uh / buh-SAL-iss)

The decidua is the modified lining of the uterus during pregnancy. The decidua basalis is the specific part that lies directly under the placenta and normally helps contain placental growth within appropriate boundaries. PAS context: PAS occurs when the decidua basalis is deficient or absent (often at a cesarean scar site), allowing placental tissue to invade deeper into the uterine wall than it should.

DIC (Disseminated Intravascular Coagulation)(dee-eye-see)

A serious medical condition in which the blood clotting system becomes overactive and then depleted, leading to both excessive clotting and dangerous bleeding throughout the body. PAS context: DIC can occur as a complication of massive hemorrhage during PAS surgery. Rapid availability of blood products is critical for treatment.

D&C (Dilation and Curettage)(dee and see)

A procedure in which the cervix is dilated (opened) and a surgical instrument is used to remove tissue from inside the uterus. Commonly used after miscarriage or for diagnostic purposes. PAS context: Prior D&C procedures may contribute to uterine scarring that increases PAS risk, though the association is weaker than with cesarean delivery. A D&C should generally be avoided when PAS is suspected, as it can cause life-threatening hemorrhage.

EBL (Estimated Blood Loss)

The amount of blood a patient loses during a surgical procedure, measured in milliliters (mL). A normal delivery typically involves 500–1,000 mL of blood loss. PAS context: Blood loss during PAS surgery can range from 2,000 to 5,000+ mL. This is why delivery at a center with a robust blood bank and massive transfusion protocol is critical.

Endometrium(en-doh-MEE-tree-um)

The inner lining of the uterus. During each menstrual cycle, the endometrium thickens in preparation for a possible pregnancy and is shed during menstruation if pregnancy does not occur. PAS context: The endometrium transforms into the decidua during pregnancy. Scarring or damage to the endometrium (from prior surgery or infection) can predispose to abnormal placental attachment.

FIGO(FEE-go)

International Federation of Gynecology and Obstetrics. The global organization for women's health professionals. FIGO has published an influential consensus classification system for PAS. PAS context: The FIGO PAS grading system (Grades 1–3) is now widely used to standardize how PAS severity is described in clinical and research settings.

Fundus(FUN-dus)

The top, rounded portion of the uterus, farthest from the cervix. PAS context: Fundal placentation (placenta attached at the top of the uterus) is less commonly associated with PAS than lower-segment placentation over a prior cesarean scar.

Gestational age(jes-TAY-shun-ul)

The age of a pregnancy measured from the first day of the last menstrual period, expressed in weeks and days. It describes how far along the pregnancy has progressed. PAS context: Planned delivery for PAS typically occurs between 34 and 36 weeks gestational age, balancing the baby's maturity against the risk of emergency bleeding.

Gravid(GRAV-id)

A medical term meaning pregnant. "Gravida" followed by a number indicates how many times a woman has been pregnant (e.g., Gravida 3 = third pregnancy). PAS context: Higher gravidity (more pregnancies), especially with multiple cesarean deliveries, is associated with increased PAS risk.

Hemorrhage(HEM-er-ij)

Severe, potentially life-threatening bleeding. Can be external (visible) or internal (within the body). PAS context: The primary danger of PAS is hemorrhage during or after delivery. This is the reason PAS requires delivery at a hospital with immediate access to massive blood transfusion and a specialized surgical team.

Histopathology(his-toh-puh-THOL-uh-jee)

The study of diseased tissue under a microscope. After surgery, a pathologist examines the removed tissue to confirm the diagnosis and determine its severity. PAS context: Histopathological examination of the uterus after hysterectomy provides the definitive (gold standard) diagnosis of PAS and its grade. Prenatal imaging can predict but not definitively confirm PAS.

Hysterectomy(his-ter-EK-tuh-mee)

The surgical removal of the uterus. It may include removal of the cervix (total hysterectomy) or leave the cervix in place (subtotal/supracervical hysterectomy). PAS context: Cesarean hysterectomy (removing the uterus at the time of cesarean delivery) is the standard and safest treatment for significant PAS. It eliminates the risk of ongoing hemorrhage but means future pregnancies are not possible.

ICU (Intensive Care Unit)

A specialized hospital unit providing close monitoring and advanced life-support care for critically ill patients. PAS context: Some patients require ICU admission after PAS surgery for close monitoring, fluid management, and recovery from significant blood loss. Having a nearby ICU is an important factor when choosing a delivery hospital.

In situ(in SIT-oo)

A Latin phrase meaning "in its place" or "in position." In medicine, it refers to something remaining in its original location. PAS context: "Leaving the placenta in situ" is a conservative management approach where the placenta is intentionally left inside the uterus after the baby is delivered, with the hope that it will be gradually reabsorbed. This carries risks and requires extensive follow-up.

Incidence

A measure of how frequently a new condition occurs in a population over a defined period of time, usually expressed as a ratio (e.g., 1 in 500 pregnancies). PAS context: The incidence of PAS has increased roughly threefold over the past 40 years, now estimated at approximately 1 in 500 pregnancies, largely driven by rising cesarean delivery rates.

Interventional radiology (IR)(in-ter-VEN-shun-ul)

A medical specialty that uses imaging techniques (such as X-ray or ultrasound) to guide minimally invasive procedures, often performed through small tubes (catheters) inserted into blood vessels. PAS context: Interventional radiologists are key members of the PAS surgical team. They may place balloon catheters in the arteries before surgery to reduce blood flow to the uterus, and they can perform embolization to control bleeding afterward.

IVF (In Vitro Fertilization)(in VEE-tro)

An assisted reproduction technique in which eggs are fertilized by sperm in a laboratory, and the resulting embryo(s) are transferred into the uterus. PAS context: IVF has been identified as a potential risk factor for PAS, particularly when embryos are transferred into a uterus with prior scarring. Women with prior cesarean sections undergoing IVF may be at increased risk.

Lacunae(luh-KOO-nee)

Irregular, fluid-filled spaces or "lakes" within the placenta that are visible on ultrasound. They often have a turbulent, swirling blood flow pattern described as "moth-eaten." PAS context: Placental lacunae are one of the most important ultrasound signs of PAS. The presence of multiple, irregular lacunae is highly suggestive of the condition and is used in diagnostic scoring systems.

MFM (Maternal-Fetal Medicine)(peri-nuh-TOL-uh-jist)

A medical subspecialty focused on managing high-risk pregnancies. MFM doctors (also called perinatologists) have additional training beyond standard obstetrics in complex pregnancy conditions. PAS context: An MFM specialist is typically the physician who leads your PAS care, coordinating diagnosis, monitoring, and delivery planning with the broader multidisciplinary team.

Morbidity(mor-BID-ih-tee)

The occurrence of health complications or disease. In research, "morbidity" refers to rates of complications associated with a condition or treatment. PAS context: Studies comparing PAS outcomes often report morbidity measures such as blood loss, ICU admission, organ injury, and length of hospital stay. Delivery at specialized centers consistently shows lower morbidity.

Mortality(mor-TAL-ih-tee)

The rate of death from a disease or condition within a defined population. Often expressed as a percentage. PAS context: Maternal mortality from PAS has decreased significantly with modern surgical and blood-banking techniques. At experienced centers, mortality rates are well below 1%.

MRI (Magnetic Resonance Imaging)

An imaging technique that uses powerful magnetic fields and radio waves (not radiation) to create detailed pictures of organs and tissues inside the body. PAS context: MRI is used as a complementary tool to ultrasound in PAS diagnosis, particularly helpful for evaluating posterior placentas, assessing the depth of invasion, and identifying bladder or parametrial involvement.

Multiparity(mul-TIP-ar-ih-tee)

Having given birth two or more times. A woman who has had multiple births is described as "multiparous." PAS context: Multiparity, especially with multiple cesarean deliveries, is a significant risk factor for PAS. Each additional cesarean increases the risk.

Myomectomy(my-oh-MEK-tuh-mee)

A surgical procedure to remove uterine fibroids (non-cancerous growths) while preserving the uterus. PAS context: Prior myomectomy creates uterine scarring similar to a cesarean section, which may increase the risk of abnormal placental implantation in subsequent pregnancies.

Myometrium(my-oh-MEE-tree-um)

The thick, muscular middle layer of the uterine wall. It is responsible for uterine contractions during labor and helps compress blood vessels after the placenta detaches. PAS context: The depth of placental invasion into the myometrium determines PAS grade. In accreta, the placenta reaches the myometrium surface. In increta, it invades into the myometrium. In percreta, it penetrates through it entirely.

Negative Predictive Value (NPV)

The probability that when a test says you do not have a condition, you truly do not have it. A high NPV means you can be reassured by a negative result. PAS context: A high NPV for PAS imaging means that when ultrasound shows no signs of PAS, there is a very good chance PAS is truly absent. See the "Understanding Diagnostic Statistics" section below for more detail.

NICU (Neonatal Intensive Care Unit)(NICK-you)

A specialized hospital unit for newborn babies who need intensive medical attention, often because they were born prematurely or with medical complications. PAS context: Because PAS deliveries often occur at 34–36 weeks (before full term), babies may need NICU care for respiratory support and feeding. A hospital with a Level III or IV NICU is preferred.

Nitabuch layer(NIT-uh-book)

A thin layer of fibrin (a protein involved in clotting) that normally forms at the junction between the decidua and the trophoblast. It serves as a natural boundary and helps the placenta separate cleanly after delivery. PAS context: In PAS, the Nitabuch layer is absent or deficient, which is believed to be a key reason the placenta cannot separate from the uterine wall.

Nulliparous(nul-IP-er-us)

Describes a woman who has never given birth. PAS context: PAS is extremely rare in nulliparous women, as the primary risk factor (uterine scarring from prior deliveries) is absent. When PAS does occur in nulliparous patients, it may be associated with prior uterine surgery or IVF.

Parity(PAIR-ih-tee)

The number of times a woman has given birth to a baby at or beyond a viable gestational age. "Para" followed by a number indicates parity (e.g., Para 2 = given birth twice). PAS context: Higher parity, especially when combined with multiple cesarean deliveries, increases the risk of PAS.

PAS (Placenta Accreta Spectrum)

An umbrella term for a group of conditions in which the placenta attaches too deeply into the uterine wall and cannot separate naturally after delivery. The spectrum includes accreta (Grade 1), increta (Grade 2), and percreta (Grade 3). PAS context: This is the central condition discussed throughout this website. The term "spectrum" reflects that PAS ranges from superficial abnormal attachment to full-thickness invasion.

Pathophysiology(path-oh-fiz-ee-OL-uh-jee)

The study of how a disease develops and progresses at a biological level — the underlying mechanisms that cause symptoms and complications. PAS context: The pathophysiology of PAS involves deficient decidua at the site of a uterine scar, allowing trophoblast cells to invade deeper than normal into (and potentially through) the myometrium.

Peripartum(peri-PAR-tum)

Occurring around the time of childbirth, generally from a few weeks before through a few weeks after delivery. PAS context: "Peripartum hysterectomy" refers to removal of the uterus performed at or very close to the time of delivery, which is the standard surgical treatment for PAS.

Placenta(pluh-SEN-tuh)

A temporary organ that develops during pregnancy, connecting the mother's blood supply to the baby via the umbilical cord. It delivers oxygen and nutrients to the baby and removes waste products. In a normal pregnancy, the placenta detaches from the uterine wall after delivery. PAS context: PAS is fundamentally a disorder of the placenta's attachment to the uterine wall. Instead of normal attachment with clean separation, the placenta grows abnormally deep.

Placenta accreta(uh-KREE-tuh)

The mildest form of PAS (Grade 1). The placenta attaches directly to the surface of the myometrium (uterine muscle) rather than staying within the decidual lining, but does not invade into the muscle itself. PAS context: Accreta accounts for approximately 75% of all PAS cases. While the mildest form, it can still cause significant hemorrhage if the placenta is forcibly removed.

Placenta increta(in-KREE-tuh)

The intermediate form of PAS (Grade 2). The placenta invades into the myometrium (uterine muscle) but does not penetrate through to the outer surface of the uterus. PAS context: Increta accounts for roughly 15% of PAS cases and is more difficult to manage surgically than accreta due to the deeper tissue involvement.

Placenta percreta(per-KREE-tuh)

The most severe form of PAS (Grade 3). The placenta grows completely through the myometrium and the serosa (outer uterine covering) and may invade adjacent organs such as the bladder, bowel, or broad ligaments. PAS context: Percreta accounts for approximately 10% of PAS cases and carries the highest risk of complications. Surgery often requires a multidisciplinary team including urologists, general surgeons, and interventional radiologists.

Placenta previa(PREE-vee-uh)

A condition in which the placenta partially or completely covers the cervical opening. This requires cesarean delivery and can cause bleeding during pregnancy. PAS context: Placenta previa in a patient with a prior cesarean section is the highest-risk combination for PAS. When previa overlies the cesarean scar, the risk of PAS may be 25–50% or higher.

Positive Predictive Value (PPV)

The probability that when a test says you do have a condition, you truly have it. A higher PPV means fewer false alarms. PAS context: PPV for PAS imaging depends on the prevalence of PAS in the population being tested. In high-risk populations (prior cesarean + previa), PPV is much higher than in low-risk screening. See the "Understanding Diagnostic Statistics" section below.

Posterior placenta

A placenta that is attached to the back wall of the uterus (the side closest to your spine). PAS context: Posterior PAS is less common but can be more challenging to diagnose by ultrasound. MRI may be particularly helpful for evaluating posterior placental invasion.

Postpartum(post-PAR-tum)

The period after childbirth, typically considered to last approximately six weeks following delivery. PAS context: Postpartum recovery from PAS surgery may be longer than from a standard cesarean, particularly if significant blood loss or additional surgical procedures were involved. Close follow-up is essential.

Postpartum hemorrhage (PPH)(post-PAR-tum HEM-er-ij)

Excessive bleeding after delivery, typically defined as blood loss greater than 500 mL after vaginal delivery or 1,000 mL after cesarean delivery. PAS context: Undiagnosed PAS is one of the most dangerous causes of PPH. When PAS is discovered unexpectedly during delivery, hemorrhage can be sudden and massive, underscoring the importance of prenatal diagnosis.

Power Doppler

An ultrasound technique that is more sensitive than Color Doppler at detecting the presence and amount of blood flow, though it does not show the direction of flow. PAS context: Power Doppler can detect low-velocity blood flow in abnormal vessels that may be missed by Color Doppler, making it useful for identifying subtle signs of PAS such as hypervascularity at the uterine-bladder interface.

RCOG(ar-cog)

Royal College of Obstetricians and Gynaecologists. The UK-based professional body for obstetrics and gynecology, which publishes influential clinical guidelines. PAS context: RCOG publishes Green-top Guidelines that include recommendations for managing PAS, widely referenced in UK and international clinical practice.

REBOA(ree-BOH-uh)

Resuscitative Endovascular Balloon Occlusion of the Aorta. A procedure in which a balloon is placed inside the aorta (the body's largest artery) to temporarily block blood flow to the pelvis and lower body. PAS context: REBOA is an emerging technique used in some PAS centers to reduce pelvic blood flow during surgery, potentially decreasing hemorrhage. Its use in PAS is still being studied.

Retroplacental clear zone

A normal, dark (hypoechoic) space visible on ultrasound between the back of the placenta and the uterine wall. It represents the normal plane of separation. PAS context: Loss of the retroplacental clear zone is one of the earliest and most commonly observed ultrasound signs of PAS. Its absence suggests the placenta is abnormally attached to the uterine wall.

Sensitivity

A measure of how well a diagnostic test correctly identifies people who do have the condition (the true positive rate). A test with 90% sensitivity will correctly detect 90 out of 100 people who have the condition. PAS context: Ultrasound has a sensitivity of approximately 80–90% for detecting PAS when performed by experienced operators. See the "Understanding Diagnostic Statistics" section below for a detailed explanation.

Serosa(suh-ROH-suh)

The thin, smooth outer covering of the uterus (also called the perimetrium). It is the outermost of the three uterine wall layers. PAS context: In percreta, the placenta penetrates through the myometrium and reaches or breaches the serosa. Loss of the normal serosal boundary on imaging is a sign of severe PAS.

SMFM(S-M-F-M)

Society for Maternal-Fetal Medicine. A U.S.-based professional organization dedicated to improving health outcomes for mothers and babies, particularly in high-risk pregnancies. PAS context: SMFM publishes clinical guidelines and consult series on PAS management that are widely used by MFM specialists across the United States.

Specificity

A measure of how well a diagnostic test correctly identifies people who do not have the condition (the true negative rate). A test with 95% specificity will correctly clear 95 out of 100 people who are healthy. PAS context: High specificity in PAS imaging means fewer unnecessary surgical preparations and less patient anxiety from false positive diagnoses. See the "Understanding Diagnostic Statistics" section below.

T2-weighted (MRI)(tee-two)

A type of MRI sequence that is particularly good at showing differences in tissue water content. Fluids appear bright and dense tissues appear dark on T2-weighted images. PAS context: Dark (hypointense) bands within the placenta on T2-weighted MRI are a key imaging sign of PAS. These bands are thought to represent fibrin deposits or areas of abnormal tissue invasion.

Trophoblast(TROH-foh-blast)

Specialized cells that form the outer layer of the developing embryo and later the placenta. Trophoblast cells normally invade the uterine wall in a carefully controlled manner to establish the blood supply needed to nourish the pregnancy. PAS context: PAS occurs when trophoblast invasion becomes uncontrolled, extending beyond the normal decidual boundary and into (or through) the myometrium. Understanding trophoblast biology is central to PAS research.

Trimester

One-third of a pregnancy. The first trimester spans weeks 1–12, the second trimester weeks 13–26, and the third trimester weeks 27–40. PAS context: PAS is most commonly diagnosed during second-trimester ultrasound screening (around 18–20 weeks). First-trimester signs can sometimes be detected, particularly a low implantation site at a prior cesarean scar.

Ultrasound (US)(UL-truh-sound)

A non-invasive imaging technique that uses high-frequency sound waves to create real-time pictures of structures inside the body. It is safe, painless, and does not use radiation. PAS context: Ultrasound is the primary tool for diagnosing PAS. Both grayscale (standard) and Doppler ultrasound techniques are used to identify characteristic signs such as lacunae, loss of the retroplacental clear zone, and abnormal vascularity.

Uterine artery embolization (UAE)

An interventional radiology procedure in which tiny particles are injected into the uterine arteries to block blood flow to the uterus. This is done through a small catheter inserted into an artery in the groin. PAS context: UAE may be used before or after PAS surgery to reduce hemorrhage. Some centers also use balloon catheters that can be inflated in the uterine or internal iliac arteries during surgery.

Uterus(YOO-ter-us)

The womb. A hollow, muscular, pear-shaped organ in the female pelvis where the fertilized egg implants and the baby develops during pregnancy. Its wall has three layers: the inner endometrium, the muscular myometrium, and the outer serosa. PAS context: PAS involves abnormal invasion of the placenta into the layers of the uterine wall. The treatment for severe PAS usually involves removal of the uterus (hysterectomy).

Understanding Diagnostic Statistics

When reading about PAS diagnosis, you will encounter statistical terms like sensitivity, specificity, PPV, and NPV. These can be confusing, so here is a plain-language guide to what they mean and why they matter to you.

The Four Possible Outcomes

Every diagnostic test produces one of four outcomes. Understanding these helps you interpret what your test results mean:

What Each Measure Tells You

Sensitivity (True Positive Rate)

Of all people who actually have PAS, what percentage does the test correctly identify?
Formula: True Positives / (True Positives + False Negatives)
For patients: A high sensitivity means the test is good at catching PAS when it exists. If sensitivity is 90%, then 10% of true PAS cases might be missed.

Specificity (True Negative Rate)

Of all people who do not have PAS, what percentage does the test correctly clear?
Formula: True Negatives / (True Negatives + False Positives)
For patients: A high specificity means fewer false alarms. If specificity is 95%, then only 5% of healthy patients will be incorrectly told they might have PAS.

Positive Predictive Value (PPV)

If your test comes back positive, what is the probability you actually have PAS?
Key insight: PPV depends heavily on how common PAS is in the group being tested. In a high-risk population (prior cesarean + previa), PPV will be much higher than in routine screening of all pregnancies.

Negative Predictive Value (NPV)

If your test comes back negative, what is the probability you truly do not have PAS?
Key insight: A high NPV is reassuring. If NPV is 98%, a negative result means there is only a 2% chance PAS was missed.

False Positive

The test suggests PAS is present when it actually is not. This can lead to unnecessary anxiety and potentially more aggressive surgical planning than needed. This is why experienced sonographers and confirmation with MRI are valuable.

False Negative

The test fails to detect PAS when it is actually present. This is more dangerous because the surgical team may not be fully prepared for the complications that PAS can cause. This is why high-risk patients should be evaluated at specialized centers.

Key Organizations & Societies

These organizations produce clinical guidelines, fund research, and provide resources related to PAS and maternal health.

Patient Resources

These resources are specifically designed for patients and families affected by PAS. They offer education, support, and practical tools to help you navigate your diagnosis.

Questions to Ask Your Doctor

Bring this list to your next appointment. Do not feel you need to ask all of them — choose the ones most relevant to your situation.

• What grade of PAS do you believe I have, and how confident are you in the diagnosis?
• Would additional imaging (MRI) help clarify the diagnosis or severity?
• How many PAS cases has your team managed in the past year?
• Who will be on the surgical team? Will there be MFM, gynecologic oncology, urology, and interventional radiology specialists present?
• What is the plan for managing blood loss? Is a massive transfusion protocol in place?
• When do you recommend I deliver, and why that timing?
• Is hysterectomy planned, or is there a possibility of uterine preservation?
• If I want to preserve my fertility, what are the realistic options and risks?
• What NICU level is available, and what should I expect for my baby?
• Should I be hospitalized before delivery, or can I stay home with monitoring?
• What signs should prompt me to come to the hospital urgently (e.g., bleeding, contractions)?
• Is there a social worker or mental health professional I can speak with about coping with this diagnosis?
• Are there PAS support groups or peer mentors you can connect me with?
• What should I expect for recovery after surgery?
• Would you recommend a second opinion or transfer to a higher-volume PAS center?

Emotional Support & Mental Health

Who Can Help

Tips for Coping

• Limit anxious internet searching. Focus on trusted resources (like this site, your medical team, and established organizations) rather than open-ended web searches that may lead to frightening anecdotes.
• Involve your partner and family. Sharing information with your support network helps them understand what you are facing and how they can help.
• Take things one step at a time. Focus on the next appointment, the next milestone. You do not need to figure everything out today.
• Keep a journal or notes. Writing down your questions, fears, and observations can help you process emotions and prepare for medical conversations.
• Celebrate your baby. Despite the medical complexity, this is still your pregnancy. Find moments to bond with your baby and look forward to meeting them.

Further Reading

For those who wish to explore the medical literature in greater depth, the following publications are among the most important and frequently cited works on PAS.

Clinical Guidelines

• ACOG & SMFM. Obstetric Care Consensus: Placenta Accreta Spectrum. Obstetrics & Gynecology, 2018. — The definitive U.S. guideline on PAS management.
• Jauniaux E, et al. FIGO consensus guidelines on placenta accreta spectrum disorders. International Journal of Gynecology & Obstetrics, 2018. — The international consensus classification and management guidelines.
• Collins SL, et al. Proposal for standardized ultrasound descriptors of abnormally invasive placenta (AIP). Ultrasound in Obstetrics & Gynecology, 2016. — Standardized terminology for PAS imaging findings.

Key Research Articles

• Silver RM, et al. Maternal morbidity associated with multiple repeat cesarean deliveries. Obstetrics & Gynecology, 2006. — Landmark study showing how PAS risk increases with each cesarean delivery.
• Shamshirsaz AA, et al. Multidisciplinary team vs. standard obstetric care for the management of placenta accreta spectrum. American Journal of Obstetrics & Gynecology, 2018. — Evidence that multidisciplinary PAS teams improve outcomes.
• Jauniaux E, et al. Placenta accreta spectrum: pathophysiology and evidence-based anatomy for prenatal ultrasound imaging. American Journal of Obstetrics & Gynecology, 2018. — Detailed explanation of PAS biology and imaging.
• Einerson BD, et al. Placenta accreta spectrum disorder: uterine dehiscence, not placental invasion. Obstetrics & Gynecology, 2020. — An influential re-thinking of PAS pathophysiology.
• Calì G, et al. ISUOG Practice Guidelines: role of ultrasound in the diagnosis of placenta accreta spectrum. Ultrasound in Obstetrics & Gynecology, 2023. — Current imaging practice guidelines.

Books

• Jauniaux E, Silver RM (eds). Placenta Accreta Spectrum. Cambridge University Press. — Comprehensive academic textbook covering all aspects of PAS.
• Silver RM, Branch DW (eds). Placenta Accreta Syndrome. CRC Press. — Multi-author clinical reference with surgical and management guidance.

Registries and Databases

• ClinicalTrials.gov — Search for "placenta accreta" to find ongoing clinical studies you may be eligible to participate in.
• PubMed — Free database of biomedical research. Search for "placenta accreta spectrum" to find published studies.

Ideas for Expanding This Site

This resource is a work in progress. Below are some of the enhancements we are considering for future versions. If any of these would be particularly valuable to you, we would love to hear about it.