Cesarean Scar Pregnancy: From a Rare Cesarean Scar Pregnancy to Placenta Accreta Spectrum

Best of the Big Apple, OB-GYN Ultrasound CME, World Class CME

One Disease – Two Completely Different Clinical Faces

Dr. Timor-Tritsch has been published extensively on topics such as transvaginal sonographic evaluation of the fetal central nervous system, cesarean pregnancy, and gynecologic ultrasound. He is the recipient of the American Institute of Ultrasound Medicine’s Joseph H. Holmes Clinical Pioneer Award, The Fry Award by the American Institute of Ultrasound Medicine, and the Ian Donald Medal by the International Society of Ultrasound in Obstetrics and Gynecology.

Dr. Timor-Tritsch is a fellow of the American College of Obstetricians and Gynecologists, the American Institute of Ultrasound Medicine, and the New York Perinatal Society.

Ilan E. Timor-Tritsch, MD
Clinical Professor of OB/GYN
Icahn School of Medicine
Mount Sinai Hospital System
Department of Obstetrics, Gynecology
and Reproductive Sciences
New York, NY

How should cesarean scar pregnancy really be managed?

Cesarean scar pregnancy (CSP) is no longer simply a rare pregnancy. It has become one of the most challenging conditions in modern obstetrics and gynecology, with profound implications for fertility preservation, hemorrhage prevention, and the development of placenta accreta spectrum (PAS).

In this comprehensive lecture, internationally recognized pioneer Professor Ilan Timor-Tritsch presents a unique perspective developed through decades of clinical experience and research.

Participants will learn:

• How to diagnose CSP accurately in the first trimester.
• Why residual myometrial thickness has become one of the most important predictors of clinical outcome.
• When CSP should be viewed as a gynecologic disease and when it evolves into an obstetrical disease.
• Which patients require immediate intervention and which may safely undergo conservative management.
• The relationship between cesarean scar pregnancy and placenta accreta spectrum.
• Practical ultrasound criteria, pitfalls, and management algorithms supported by the latest evidence.

Using numerous real clinical cases, surgical correlations, and long-term follow-up, this lecture provides practical guidance that can immediately improve patient care and help avoid potentially catastrophic complications.

Whether you are an obstetrician, gynecologist, maternal-fetal medicine specialist, or ultrasound practitioner, this session will fundamentally change the way you diagnose, classify, and manage cesarean scar pregnancy.

Don’t miss this state-of-the-art lecture at Ultrasound of the Big Apple 2026.

A useful conceptual distinction between the gynecological and obstetrical clinical aspects of cesarean scar pregnancy: Highlights from the two lectures on Cesarean Scar Pregnancy.

Cesarean scar pregnancy (CSP) is always a pregnancy implanted in or immediately adjacent to a previous cesarean scar. However, its dominant clinical character changes with its course. When the pregnancy is nonviable, miscarries, or is actively terminated in the first trimester, its diagnosis, treatment, and follow-up largely resemble those of a complex gynecologic ectopic pregnancy. When a viable CSP is continued, the problem evolves into a high-risk obstetric pregnancy dominated by progressive placentation at a deficient lower-uterine-segment scar, with substantial risk of placenta accreta spectrum (PAS), hemorrhage, uterine dehiscence or rupture, preterm delivery, and hysterectomy. This is a clinically helpful division, although it is not a formal change in the biological diagnosis.

Gynecologic aspects of cesarean scar pregnancy

In its early presentation, CSP is principally an early-pregnancy and gynecologic diagnostic problem. Patients may be asymptomatic or present with vaginal bleeding, pelvic pain, or both. Transvaginal ultrasound is the best and primary diagnostic modality and should establish the relationship of the gestational sac to the endometrial cavity, cesarean scar or niche, cervix, bladder, and residual anterior myometrium. Important sonographic features include an empty or nearly empty main uterine cavity, implantation in the anterior lower uterine segment at the scar, prominent peri trophoblastic vascularity, and reduced or absent residual myometrial thickness between the gestation and the bladder. Correct early diagnosis is essential because CSP may be mistaken for a low intrauterine pregnancy, cervical pregnancy, incomplete miscarriage, or retained products of conception.

Once a decision is made to terminate the pregnancy—or once spontaneous pregnancy failure has occurred—the immediate clinical goals are to remove or inactivate the gestational tissue, control hemorrhage, preserve the uterus and fertility where desired, and avoid unnecessary morbidity. Available treatments include ultrasound-guided uterine aspiration, operative hysteroscopy, laparoscopic or transvaginal resection, local intragestational injection, balloon compression, vascular control procedures, and selected combined approaches. The literature remains heterogeneous, and no single treatment is optimal for every patient; choice depends on gestational age, embryonic cardiac activity, residual myometrial thickness, vascularity, sac size and direction of growth, bleeding, hemodynamic stability, fertility wishes, and local expertise. The Society of Maternal Fetal Medicine (SMFM) recommends against expectant management as routine care and also recommends against systemic methotrexate alone. Operative resection or ultrasound-guided uterine aspiration and, when appropriate, intragestational methotrexate are among the suggested approaches.

Blind sharp curettage is particularly problematic because the pregnancy may lie predominantly within the scar or niche rather than freely within the endometrial cavity. Instrumentation may therefore fail to remove the trophoblastic tissue and may provoke severe hemorrhage or perforation. When uterine evacuation is selected, ultrasound guidance, suction rather than sharp curettage, availability of balloon tamponade, and immediate access to surgical or interventional-radiologic support improve safety.

Follow-up is also primarily gynecologic. Resolution should be assessed by symptoms, serial quantitative serum hCG, and ultrasound. A vascular implantation-site mass or enhanced myometrial vascularity may persist for weeks or months, even after embryonic demise or treatment. Persistence does not automatically indicate a congenital uterine AVM and should not, in an otherwise stable patient, trigger immediate embolization or hysterectomy. The clinician must distinguish resolving trophoblastic tissue and postpregnancy vascular remodeling from retained products, active bleeding, pseudoaneurysm, gestational trophoblastic disease, and a rare true vascular malformation.

The long-term gynecologic consequences include scar-niche persistence, intrauterine adhesions after treatment, menstrual abnormalities, reduced fertility in some patients, and recurrent CSP. Patients planning another pregnancy should be counseled to obtain very early transvaginal ultrasound—commonly at approximately 5–7 weeks—to document implantation before the pregnancy enlarges. The subsequent pregnancy should not be considered “routine” until normal implantation away from the scar is demonstrated. Early diagnosis and counseling are therefore central elements of the gynecologic management of CSP.

Obstetrical aspects of cesarean scar pregnancy

When a viable CSP is managed expectantly, it should no longer be approached as an uncomplicated early intrauterine pregnancy. It becomes a high-risk obstetric condition, because the gestational sac may expand toward the uterine cavity while the placenta remains anchored in the cesarean scar or niche. With advancing gestation, the early scar implantation may evolve into a low anterior placenta or placenta previa with PAS beneath a markedly thinned or dehiscent lower uterine segment. The sonographic appearance changes with gestational age, but the abnormal implantation site and deficient uterine wall remain the foundation of the later obstetric risk.

The best available evidence indicates that expectant management can occasionally result in a live birth, but at the cost of substantial maternal and fetal morbidity.

A systematic review found PAS to be common among expectantly managed CSPs and associated with fetal death, preterm birth, hemorrhagic morbidity, surgical complications, and hysterectomy. Worse outcomes were associated in several studies with implantation “in the niche,” more exophytic growth, lower residual myometrial thickness, and higher-risk sonographic classifications.

Not all CSPs have identical obstetric behavior. Pregnancies implanted “on the scar,” with appreciable intervening myometrium and growth predominantly toward the uterine cavity, may have better outcomes than pregnancies implanted deeply “in the niche,” with little or no residual myometrium and expansion toward the bladder. Selected observational studies have therefore suggested that expectant management might be considered only in exceptionally well-counseled patients with favorable anatomy, such as thicker residual myometrium and implantation on rather than within the scar.

If pregnancy continuation is chosen after fully informed counseling, management should include:

• referral to a tertiary center experienced in CSP and PAS;
• serial transvaginal and transabdominal ultrasound to assess placental location, residual myometrium, bladder interface, vascularity, fetal growth, cervical length, and signs of dehiscence;
• counseling about sudden hemorrhage, uterine rupture, pregnancy loss, very preterm delivery, transfusion, bladder or ureteral injury, intensive-care admission, and hysterectomy;
• early multidisciplinary planning involving maternal-fetal medicine, gynecologic or pelvic surgeons, anesthesia, neonatology, blood bank, interventional radiology where appropriate, and urology if bladder involvement is suspected;
• avoidance of labor and avoidance of attempted manual placental separation when significant PAS is anticipated;
• delivery planning according to the degree of PAS, bleeding, symptoms, fetal status, and local PAS protocols.

Thus, the obstetric problem is not simply whether the fetus can survive. The central issue is whether a pregnancy originating in a cesarean scar can be carried to viability without exposing the mother to disproportionate risk. Live birth is possible, but expectant management converts an early focal implantation disorder into a prolonged pregnancy at risk for PAS and major hemorrhagic surgery.