First-Trimester Cesarean Scar Pregnancy Evolving Into Placenta Previa/Accreta at Term

Case Report First-Trimester Cesarean Scar Pregnancy Evolving Into Placenta Previa/Accreta at Term Jara Ben Nagi, MD, Dede Ofili-Yebovi, MD, Mike Marsh, MD, Davor Jurkovic, MD Placenta accreta is a rare but serious obstetric condition that is associated with considerable maternal morbidity and mortality. 1 A preoperative diagnosis of placenta accreta is difficult, and it is usually established at cesarean delivery or on histologic examination after obstetric hysterectomy for postpartum hemorrhage. In women with placenta previa, an abnormally adherent placenta is suspected when there is an absent decidual interface between the placenta and the myometrium. Another sign is the presence of unusually dilated vessels at the placental site. 2,3 Although the reported accuracy of sonographic diagnosis in the third trimester is reasonably high, late detection is of limited value because it does not prevent the serious complications of placenta accreta. The first-trimester diagnosis of pregnancy implantation in a previous cesarean delivery scar has been reported in recent years. 4,5 This condition is difficult to differentiate from cervical pregnancy, and it is likely that before the use of high-resolution transvaginal sonography, cesarean scar pregnancies were diagnosed and treated as cervical ectopic pregnancies. Cervical pregnancies rarely progress to term, whereas cesarean scar pregnancies may do so because of their position at the level of the internal os. In 60% to 70% of cesarean scar pregnancies, there is clear evidence of trophoblast penetrating the endometrial-myometrial junction. It has been postulated that firsttrimester cesarean scar pregnancies that invade the myometrium may develop into placenta previa/accreta if the pregnancy is allowed to progress. 5 In this report, we describe the case of a first-trimester cesarean scar pregnancy with evidence of myometrial involvement that was managed expectantly and developed into placenta previa/accreta at term. Case Report Received April 26, 2005, from the Early Pregnancy and Gynaecology Assessment Unit (J.B.N., D.O.-Y., D.J.) and Department of Obstetrics and Gynecology (M.M.), King s College Hospital, London, England. Revision requested May 31, 2005. Revised manuscript accepted for publication June 16, 2005. Address correspondence to Davor Jurkovic, MD, Early Pregnancy and Gynecology Assessment Unit, King s College Hospital, Denmark Hill, London SE5 8RX, England. E-mail: davor.jurkovic@kcl.ac.uk A 37-year-old woman, gravida 6, para 3, with a history of vaginal bleeding at 5 weeks gestation was admitted for an early sonographic scan. The pregnancy was planned, and the size of the gestational sac corresponded to her certain menstrual dates. She had undergone 3 cesarean deliveries in the past. The first was an emergency cesarean delivery at 40 weeks for fulminating preeclampsia. Subsequently, she had 2 elective cesarean deliveries at term, both of which were performed because of the his- 2005 by the American Institute of Ultrasound in Medicine J Ultrasound Med 2005; 24:1569 1573 0278-4297/05/$3.50

Placenta Previa/Accreta at Cesarean Scar tory of previous emergency cesarean delivery. All of her children were living and healthy. She also had 2 first-trimester miscarriages before the current pregnancy that were treated by evacuation of the retained products of conception. Her gynecologic and medical histories were unremarkable. First Trimester A transvaginal scan performed at a gestational age of 5 weeks 5 days revealed a 3.7-mm gestational sac. The sac was located at the level of the internal os. There was a wide gap in the anterior myometrium, which was covered only by a thin layer of echogenic tissue. The gestational sac was implanted into this gap, which was presumed to represent a deficient uterine cesarean delivery scar. In view of the small size of the sac and the history of vaginal bleeding, it was believed that there was a good chance that the pregnancy would miscarry. A decision was therefore made to continue with expectant management and to repeat the scan 1 week later. The patient continued to have intermittent vaginal bleeding. At 6 weeks 3 days, she returned for another scan, which showed a viable embryo within the gestational sac. The sac was embedded deep within the myometrium and completely filled the myometrial defect (Figure 1). In view of these findings, she was informed that the pregnancy could develop into placenta previa/accreta and that she would be at risk of having major hemorrhaging that would require a hysterectomy if the pregnancy were allowed to progress. After discussion, the patient decided to continue with the pregnancy and was asked to return 2 weeks later for another scan. A follow-up sonographic scan was performed at 8 weeks 4 days, by which time the vaginal bleeding had stopped (Figure 2). On the sonographic scan, the embryo was developing normally. The placenta was seen herniating through the left anterolateral aspect of the uterine wall toward the bladder and the left adnexa. Once again, she was counseled about the risks of serious complications later in pregnancy, but she decided to continue with expectant management. An antenatal visit was arranged, and she was also scheduled for a routine nuchal translucency scan. Second Trimester The patient returned to the fetal medicine unit for a nuchal scan at 12 weeks 5 days. The fetus appeared normal, and the estimated risk of trisomy 21 was 1:732. She was reassured by this result and decided against invasive testing for chromosomal abnormalities. She returned at 14 weeks 5 days for shared hospital care. At admission, her blood pressure was 125/80 mm Hg, her hemoglobin level was 12.6 g/dl, and she had a positive test result for sickle cell trait. Her blood group was A, RH D-positive, and she had positive test results for anti-m antibodies. She was then seen at regular 4-week intervals by her community midwife. She remained asymptomatic and had a fetal anoma- Figure 2. Longitudinal section of the uterus showing the gestational sac implanted in the anterior uterine wall. The trophoblast is herniating toward the left adnexa through the gap in the myometrium. Figure 1. Sonographic image at 6 weeks gestation showing the sac filling the myometrial defect. 1570 J Ultrasound Med 2005; 24:1569 1573

Nagi et al ly scan at 22 weeks 5 days, which showed no evidence of fetal structural defects; however, the placenta was noted to be low. Third Trimester The pregnancy continued without complications, and she returned to our unit for another scan at 26 weeks. The scan revealed an anterior placenta previa with a thin, bulging, and deficient lower uterine segment (Figure 3). The decidual interface between the placenta and the myometrium was partially absent, and there were large dilated blood vessels in the same area. These sonographic features were suggestive of a placenta accreta. She remained generally well, and 2 additional scans at 34 and 36 weeks confirmed the diagnosis of placenta previa/accreta. A decision was made to admit her for an elective cesarean delivery at 37 weeks 5 days. Her preoperative hemoglobin level was 10.3 g/dl. Four units of blood were cross-matched. Cesarean Delivery The operation was performed under general anesthesia. The entry into the peritoneal cavity was difficult because of the presence of scar tissue. The bladder was adherent to the lower uterine segment. The myometrium of the lower segment was severely deficient. The placenta protruded toward the left adnexa and was covered with a thin layer of peritoneum. The bladder was dissected from the uterus, and the lower segment was incised. A healthy male neonate weighing 3.4 kg was delivered, with Apgar scores of 4 and 8 at 1 and 5 minutes, respectively. The placenta was firmly adherent to the myometrium from which it could not be separated completely (Figure 4). Severe hemorrhage ensued and could not be contained by uterotonics and conservative surgical measures; therefore, a decision was made to perform an emergency subtotal hysterectomy. The estimated blood loss was approximately 3500 ml, but the operation was otherwise uncomplicated. Two units of blood were transfused intraoperatively. Her postoperative hemoglobin level was 7.8 g/dl, but the recovery was otherwise uneventful. She was discharged to home 4 days later, and iron tablets were prescribed. Histologic Findings Macroscopic examination of the uterus showed that the lower uterine segment was dilated. On the left lateral side of the uterine wall, a 6 5-cm area of the myometrium measured only 0.3 cm in thickness and was covered by adherent blood. Microscopic analysis of the lower uterine segment sections revealed the presence of intermediate trophoblast and mature chorionic villi, which were extending deep into the myometrium. No chorionic villi were found within the uterine cavity. The final histologic diagnosis was placenta increta. Figure 3. Sonographic image at 26 weeks gestation revealing anterior placenta previa with large dilated blood vessels in the anterior uterine wall, which is suggestive of placenta accreta. Figure 4. At the time of the cesarean delivery after the birth, the placenta remains firmly adherent to the myometrium, which is typical of placenta accreta. J Ultrasound Med 2005; 24:1569 1573 1571

Placenta Previa/Accreta at Cesarean Scar Postnatal Visit At a follow-up visit 6 weeks after the operation, the patient was well, and her abdominal incision was completely healed. She was advised to continue with routine smear tests in the future, and no further visits were arranged. She was asked for permission to present her case for publication to a scientific journal, and she gave her verbal consent. Discussion Our case shows that a successful diagnosis of placenta previa/accreta developing within a deficient cesarean delivery scar can be made during the first trimester of pregnancy. The criteria for a diagnosis of pregnancy implantation into uterine cesarean delivery scars have been described previously and include the visualization of a defect within the anterior uterine wall. 6 The diagnosis of pregnancy implantation in a deficient scar is not difficult during the first few weeks of pregnancy because the gestational sac is very small, and the implantation site can be identified accurately. Furthermore, the lower segment is relatively thick, which facilitates the detection of a myometrial defect. At present, it is impossible to speculate whether a first-trimester diagnosis of placenta previa/accreta is more accurate and reproducible compared with a second-trimester diagnosis; however, it is interesting that in this case the diagnosis of abnormally adherent placenta was not suspected on transabdominal scans performed during the second trimester in our tertiary referral fetal medicine unit. It is unclear whether pregnancy implantation over an apparently well-healed cesarean scar is also likely to result in placenta previa/accreta at term. Most cases of first-trimester cesarean scar pregnancies reported in the literature have been managed actively with surgical or medical treatment. This approach has been justified by the generally poor outcomes of these pregnancies and an increased risk of hemorrhage and hysterectomy with increasing gestation. 7 In 7 women who were managed expectantly either by patient choice or because of a missed diagnosis, the hysterectomy rate was 71%. 4,5,8 10 The association between previous cesarean delivery and abnormally adherent placenta is well known. Clark et al 11 reported that the incidence of abnormally adherent placentas is 30% to 40% when the placenta is implanted over the uterine scar. It has also been shown that abnormally adherent placentas account for 50% to 65% of all obstetric hysterectomies, 66% of which have a history of previous cesarean deliveries. 12 The clinical importance of this complication is also illustrated by the most recent United Kingdom Confidential Enquiry into Maternal Deaths, 13 which showed that 4 women died of placenta previa between 2000 and 2002. All of them had at least 1 previous cesarean delivery, with a histologic diagnosis of placenta accreta in 3 (75%) of 4 cases. A first-trimester diagnosis of abnormal placentation gives women the option to choose between expectant management and termination of pregnancy. Termination of pregnancy during the first trimester is complicated by substantial hemorrhage in 20% to 40% of cases, but the risk of hysterectomy is low. The possibility of conserving the uterus is important to women who have not completed their families; however, should the woman opt for expectant management, antenatal care should be similar to that of other women with the diagnosis of major placenta previa. Early diagnosis helps ensure that senior medical staff are present at the time of delivery or miscarriage should an obstetric hysterectomy be required. This may not reduce the risk of hysterectomy, but it is likely to decrease the chance of surgical complications and death. References 1. Miller D, Chollet J, Goodwin TM. Clinical risk factors for placenta praevia-placenta accreta. Am J Obstet Gynecol 1997; 177:210 214. 2. Jauniaux E, Toplis PJ, Nicolaides KH. Sonographic diagnosis of a non-praevia placenta accrete. Ultrasound Obstet Gynecol 1996; 7:58 60. 3. Lerner JP, Deane S, Timor-Tritsch I. Characterization of placenta accrete using transvaginal sonography and color Doppler imaging. Ultrasound Obstet Gynecol 1995; 5:198 201. 4. Godin P, Bassil S, Donnez J. An ectopic pregnancy developing in a previous Caesarean section scar. Fertil Steril 1997; 67: 398 400. 5. Jurkovic D, Hillaby K, Woelfer B, Lawrence A, Salim R, Elson C. First trimester diagnosis and management of pregnancies implanted into the lower uterine segment cesarean section scar. Ultrasound Obstet Gynecol 2003; 21:220 227. 1572 J Ultrasound Med 2005; 24:1569 1573

Nagi et al 6. Vial Y, Petignat P, Hohlfeld P. Pregnancy in a cesarean scar. Ultrasound Obstet Gynecol 2000; 16:592 593. 7. Maymon R, Halperin R, Mendlovic S, Schneider D, Herman A. Ectopic pregnancies in a Caesarean scar: review of the medical approach to an iatrogenic complication. Hum Reprod Update 2004; 10:515 523. 8. Herman A, Weinraub Z, Avrech O, Maymon R, Ron- El R, Bukovsky Y. Follow up and outcome of isthmic pregnancy located in a previous Caesarean section scar. Br J Obstet Gynecol 1995; 102:839 841. 9. Jelsema R, Zuidema L. First trimester diagnosed cervico-isthmic pregnancy resulting in term delivery. Obstet Gynecol 1992; 80:517 519. 10. Seow K, Huang L, Lin Y, Tsai Y, Hwang J. A Caesarean scar pregnancy: issues in management. Ultrasound Obstet Gynecol 2004; 23:247 253. 11. Clark SL, Koonings PP, Phelan JP. Placenta previa/accreta and prior Caesarean section. Obstet Gynecol 1985; 66:89 92. 12. Zelop C, Bernard L, Harlow L, et al. Emergency peripartum hysterectomy. Am J Obstet Gynecol 1993; 168:1443 1448. 13. Lewis G (ed). Why Mothers Die: Reports on Confidential Enquiries into Maternal Deaths in the United Kingdom 1997 2002. London, England: Her Majesty s Stationery Office; 2000 2002. J Ultrasound Med 2005; 24:1569 1573 1573