Sonographic Diagnosis of CesareanScar Pregnancy at 16 Weeks

Alison Smith, DMU,1 Alok Ash, FRCOG,2 Darryl Maxwell, FRCOG3

1 Emergency Gynaecology Unit, St. Thomas’ Hospital, London SE1 7EH, United Kingdom2 Department of Obstetrics, St. Thomas’ Hospital, London SE1 7EH, United Kingdom3 Fetal Medicine Unit, St. Thomas’ Hospital, London SE1 7EH, United Kingdom

Received 3 January 2006; accepted 27 July 2006

ABSTRACT: Cesarean scar pregnancy is rare. How-

ever, there has been a rapid increase in the reporting

of such cases in recent years. Most of the cases

reported in the literature were diagnosed early in the

first trimester. Possible management options pro-

posed are pertinent to an early diagnosis. We present

a case of a cesarean scar pregnancy diagnosed at

16 weeks that posed a dilemma with regard to man-

agement. The patient subsequently suffered a rup-

tured uterus, which was preserved at surgery. VVC 2007

Wiley Periodicals, Inc. J Clin Ultrasound 35:212–215,2007; Published online in Wiley InterScience (www.

interscience.wiley.com). DOI: 10.1002/jcu.20270

Keywords: ultrasound; diagnosis; cesarean scar pre-

gnancy; ectopic pregnancy; second trimester

Cesarean scar pregnancy is an implantation ofthe blastocyst in the microscopic dehiscent

scar secondary to a previous cesarean section.With the increased use of cesarean section, thepossibility of ectopic implantation is raised. Anunderstanding of the sonographic appearances ofcesarean scar pregnancy and the differential di-agnosis is important. The management optionsare somewhat dependent upon early diagnosis.We present a case of cesarean scar pregnancythat was diagnosed at 16 weeks.

CASE REPORT

The patient was a 31-year-old woman in her sec-ond planned pregnancy who had undergone an

elective cesarean section 4 years previously. Anuchal translucency scan performed at 12 weeksat her local hospital revealed a low risk of Downsyndrome and was otherwise unremarkable. Alarge bleed per vaginum occurring at 16 weekshad prompted her to present at the EmergencyGynaecology Unit of our institution. The patientcomplained of a constant ache in her lower abdo-men and back since 10 weeks’ gestation. Trans-abdominal sonographic examination performedwith an Antares scanner (Siemens Acuson,Mountain View, CA) and a C4-1 curved-arraytransducer demonstrated a live single fetus. Fe-tal biometry was appropriate for the menstrualdates. Amniotic fluid volume was normal. Thepregnancy was located low in the uterus andthe empty endometrial cavity was visualizedsuperior to the gestation sac (Figure 1). The ante-rior placenta did not show the usual hypoechoicappearances of the retroplacental zone (Figure2). Transvaginal sonograms confirmed theseplacental appearances. In addition, a long closedcervix was demonstrated. The internal os was dif-ficult to visualize. Color and power Doppler anal-ysis revealed hypervascularity at the placenta–bladder interface (Figure 3). Based on these find-ings, a diagnosis of cesarean scar pregnancy wassuspected.

The patient was admitted to the hospital be-cause she was considered to be at risk for anacute obstetric emergency. Possible managementoptions included performing an immediate feti-cide and excising the pregnancy sac or continuingwith the pregnancy and aiming for an early deliv-ery, via hysterotomy, before 30 weeks’gestation.The patient was counseled regarding the risks ofuterine rupture, hysterectomy, and associated

Correspondence to: A. Smith

' 2007 Wiley Periodicals, Inc.

212 JOURNAL OF CLINICAL ULTRASOUND—DOI 10.1002/jcu

Case Report

maternal morbidity. She made an informedchoice to continue with the pregnancy withoutintervention. Two weeks later, at 18 weeks’ gesta-tion, she collapsed with acute lower abdominalpain and was transferred to the operating room.Laparotomy via a midline incision revealed pro-fuse bleeding in the peritoneal cavity. The uteruswas opened via a midline incision. The dead fe-tus, placenta, and blood clots were removed fromthe lower uterine cavity, followed by repair of theuterine wound. The patient’s estimated blood losswas 2 l. She made a slow but satisfactory recov-ery, requiring 7 units of blood transfusion and 2units of fresh frozen plasma, and was dischargedon day 11.

DISCUSSION

Trauma to the myometrium caused by dilatationand curettage,1 myomectomy, cesarean section, orconditions such as adenomyosis has been proposedas a risk for a gestation implanting within the myo-metrium instead of the endometrial cavity. It isassumed that the blastocyst enters the myome-trium through a microscopic dehiscent scar. Thetrue incidence of cesarean scar pregnancy is notknown, because there have been limited reports inthe literature. With the recent widespread use oftransvaginal imaging in early pregnancy, thereporting of such cases has increased. The differen-tial diagnoses are those of a spontaneous miscar-riage or cervico-isthmic pregnancy. The criteria fordiagnosis of cesarean scar pregnancy via transvagi-nal sonography include (1) an empty uterine cavity;(2) the gestational sac located at the level of the in-ternal os, at the site of the previous lower segmentcaesarean section scar; (3) functional trophoblastictissue demonstrated on Doppler sonography; and(4) a negative ‘‘sliding organs’’ sign,2 which isdescribed as the inability to displace the gestationalsac from its position at the level of the internal oswith gentle pressure applied by the endovaginalprobe. Placenta accreta is the invasion of thedecidua basalis and penetration of the myome-trium by the placental villi. The incidence increaseswith placenta previa and previous cesarean sec-tion. The sonographic features of placenta accretahave been described as a loss of the hypoechoicappearance of the retroplacental zone and the pres-ence of intraplacental vascular lacunae.3 In ourcase, whereas there was a loss of the hypoechoicappearance of retroplacental zone, there was no

FIGURE 1. Sagittal sonogram of the uterus demonstrates the fetus

(thin arrow) and the anterior placenta (thick arrow) within the gesta-

tional sac, which lies inferior to the endometrial cavity (short lines)

containing a blood clot (asterisk).

FIGURE 2. Sagittal view of the uterus shows the anterior placenta

(thick arrow) with loss of hypoechoic appearances of the retroplacen-

tal zone (thin arrows).

FIGURE 3. Transvaginal sagittal color Doppler sonogram of the lower

uterus shows hypervascularity of the placenta–bladder interface.

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evidence of intraplacental vascular lacunae. Theempty uterine cavity was clearly visualized sepa-rately and was superior to the gestational sac, indi-cating a cesarean scar pregnancy.

Our case presented at 16 weeks’gestation andwas diagnosed transabdominally, whereas the ma-jority of previously reported cases have beendetected in the first trimester using transvaginalimaging.2,4–6 In a series of 18 cases, 2 presentedafter 12 weeks’ gestation, at 14 and 23 weeks,respectively, and both were nonviable pregnanciesconsisting of retained placental tissue after firsttrimester embryonic demise.2 Marcus et al7

described a woman complaining of pain and vagi-nal bleeding presenting at 13 weeks’ gestationwith a viable pregnancy in whom cesarean scarpregnancy was diagnosed. This case has similar-ities to our own in that an earlier scan erroneouslydiagnosed an intrauterine gestation, with thepatient presenting later with early pregnancycomplications that prompted a search for theunderlying cause. However, the clinical presenta-tion of cesarean scar pregnancy is not alwayssymptomatic. In several previously reported cases,the diagnosis was made during routine early preg-nancy scanning in asymptomatic women.6

It has been postulated that a higher number ofprevious cesarean sections increases the likeli-hood of a pregnancy implanting in the scar.2 Ithas also been suggested that a cesarean scarpregnancy may occur as a result of incompletehealing of the uterine scar. Therefore, by infer-ence, a shorter time elapsing between previouscesarean section scar and subsequent pregnancywould increase the likelihood of a scar implanta-tion.8 Interestingly, our patient had only 1 previ-ous cesarean section, 4 years previously. Treat-ment options of cesarean scar pregnancy includemedical, surgical, or expectant management.Medical treatment includes methotrexate admin-istered systemically and/or locally.2,5,6 Viablepregnancies can be injected with potassium chlo-ride before methotrexate treatment.2 Unsuccess-ful medical treatment requires subsequent surgi-cal management. Surgical options include lapa-rotomy and excision of the gestational mass,4

suction curettage,2 or laparoscopy.9

There have been few reports of viable cesareanscar pregnancies managed expectantly. Hermanet al10 reported a cesarean scar pregnancy diag-nosed at 7 weeks’ gestation in which the implan-tation of the gestational sac on the scar wasbelieved to be toward the cervico-isthmic spaceand, with advancing gestation, would eventuallycoalesce. Therefore, it was planned to manageexpectantly and to deliver via cesarean section at

35 weeks’ gestation. At 34 weeks’ gestation, anemergency cesarean section was indicated becauseof acute abdominal pain, and a healthy infant wasdelivered. Because of intraoperative bleeding, ahysterectomy was performed.

Vial et al4 suggest that there are 2 differingdegrees of implantation. One is implantation ofthe amniotic sac on a scar with progression ofthe pregnancy toward the cervico-isthmic spaceand uterine cavity; the other is a deeper implan-tation in a cesarean scar defect. These typicallyresult in rupture and bleeding during the firsttrimester. In our case, it was not possible at 16weeks to visualize the scar transabdominallyand to evaluate the degree of implantation in amanner that is feasible transvaginally in thefirst trimester.

Few data exist relating to the true incidence ofcesarean scar pregnancy. There have been over80 cases reported in the literature; however, only19 occurred between 1966 and 2002.8 The major-ity of these cases have been reported within thelast 3 years. Most cases are diagnosed in the firsttrimester via transvaginal sonography. Womenwith a history of cesarean section are at risk forcesarean scar pregnancy, and our case highlightsthe need for an awareness of such findings. Therisk of uterine rupture and the associated seque-lae pose a challenge to provide the safest outcomein terms of limiting maternal morbidity and pre-serving future fertility. The experiences of Her-man et al indicate that expectant managementhas a poor prognosis, with a high risk to maternalwell-being and of emergency hysterectomy. Theoutcome of our case reinforces the poor prognosisfor caesarean scar pregnancy detected in the sec-ond trimester and managed expectantly.

REFERENCES

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2. Jurkovic D, Hillaby H, Woelfer B, et al. First-trimester diagnosis and management of pregnan-cies implanted into the lower uterine segment cesar-ean section scar. Ultrasound Obstet Gynecol 2003;21:220.

3. Finberg H, Williams J. Placenta accreta: prospec-tive sonographic diagnosis in patients with pla-centa previa and prior caesarean section. J Ultra-sound Med 1992;11:333.

4. Vial Y, Petignat P, Hohlfeld P. Pregnancy in a ce-sarean scar. Ultrasound Obstet Gynecol 2000;16:592.

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5. Seow K, Huang L, Lin Y, et al. Cesarean scar preg-nancy: issues in management. Ultrasound ObstetGynecol 2004;23:247.

6. Maymon R, Halperin R, Mendlovic S, et al. Ectopicpregnancies in cesarean section scars: the 8 year ex-perience of one medical centre. Human Reprod 2004;19:278.

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8. Fylstra D. Ectopic pregnancy within a cesareanscar: a review. Obstet Gynecol Surv 2002;57:573.

9. Lee C-L, Wang C-J, Chao A, et al. Laparoscopicmanagement of an ectopic pregnancy in a previouscaesarean section scar. Human Reprod 1999;14:1234.

10. Herman A, Weinrub Z, Arech O, et al. Follow-upand outcome of isthmic pregnancy located in a pre-vious section scar. Br J Obstet Gynecol 1995;102:839.

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