Cervico-isthmic pregnancy with cervical placenta accreta

Introduction

Cervical pregnancies including both true cervical and cervico-isthmic pregnancies remain a rare implantation disorder. The reported incidence varies from 1 in 1000 to 1 in 18,000 affecting approximately 1% of all ectopic pregnancies [2, 4].

Notwithstanding the rare incidence rate of this anomaly the diagnostic criteria in the first trimester are well-known. Both Oyelese et al. [5] and Strobelt et al. [6] proposed that a true cervical pregnancy exists if the gestational sac is confined to the cervix. Other authors have suggested that cervical pregnancy should be suspected if there are poorly circumscribable intrauterine structures, an enlarged uterus, absence of intrauterine pregnancy as well as a distended cervix. The diagnosis can be made by transvaginal ultrasound as early as 7 weeks into gestation [1]. In contrast to cervico-isthmic pregnancy a true cervical pregnancy with delivery at term is considered impossible.

Abnormal implantation of the placenta into the uterine wall results in placenta accreta, increta, and percreta. Probable risk factors for both abnormal implantation and localization include curettage, Asherman’s syndrome, previous cesarean delivery, previous cervical or uterine surgery, and in vitro fertilization. Complications include damage to adjacent organs (bladder, ureters, and bowel) and massive hemorrhage leading to cesarean hysterectomy [4].

Implantation disorders, such as placenta accreta, increta or percreta, in cervical pregnancies are explained by the absence of a protective decidua basalis in the cervix which results in trophoblastic invasion into the cervical tissue. One has to assume that there is also an elevated risk of fetal presentation anomalies, premature rupture of membranes or cord implantation disorders similar to placenta previa.

During the course of a pregnancy affected by cervical placenta typical clinical symptoms include painless bleeding. After delivery the absence of contractile tissue in the cervix can result in massive bleeding requiring a hysterectomy. Maternal mortality has been reported as high as 50% [1].

However, because most cervical pregnancies abort spontaneously or are terminated diagnostic criteria in the second and third trimester are lacking.

We report a case about the management of a cervico-isthmic pregnancy.

Case report

A 35-year-old woman (gravida III, para I) was referred to our department at 19+5 gestational weeks with cervical shortening. In addition, the patient reported episodes of painless vaginal bleeding during the course of her pregnancy. Her past obstetric history showed two miscarriages with curettages and her medical history a Factor-V-Leiden coagulopathy. Therefore, she was treated with low-molecular-weight heparin (Dalteparin 5000 IE, once daily s.c.). The placental implantation site was completely located in the cervix and the uterine isthmus while the fetus developed in the uterus (Figure 1A). Other findings of the placenta were placental lacunae and a thin myometrial layer in transvaginal ultrasound (2 mm, not shown) adjacent to the bladder without signs of myometrial invasion suspecting placenta accreta. The remaining cervical length was 13 mm (not shown). The results of a fetal ultrasound scan were unremarkable (GE Voluson E8 ultrasound system, General Electric Healthcare, Waukesha, WI, USA and Sonoace Accuvix V20 ultrasound system, Medison Co., Ltd., Daechi-Dong Kangnam-Gu, Seoul, Korea). We also performed magnetic resonance imaging (MRI) (Philips Panorama, high field open MRI, Koninklijke Philips Electronics N.V., Eindhoven, The Netherlands) which confirmed our sonographic findings (Figure 1B).

Figure 1

(A) Transabdominal ultrasound scan showing the location of the placental implantation site in the cervix and the uterine isthmus leading to distension of cervical tissue (cervical region marked by white stars). (B) Corresponding T2-weighted MR image showing multiple placental lacunae (marked by black star).

The patient was hospitalized for further surveillance. After counseling, the couple opted to continue with the pregnancy. At 23+5 weeks of gestation she received one cycle of betamethasone for fetal lung maturation (2×12 mg in 24 h i.m.). During hospitalization, the course of her pregnancy was complicated by two episodes of painless vaginal bleeding, which ceased spontaneously. To prevent recurrent bleeding oral tocolytics (30 mg nifedipine TID) were administered. A cesarean section was planned for 34+0 weeks of gestation. At 31+5 weeks of gestation the patient developed brisk vaginal bleeding with sonographic signs of placental abruption and thus an emergency cesarean section by median laparotomy and fundal transverse hysterotomy was performed, allowing the delivery of a girl weighing 1645 g, with Apgar scores of 7 at 1 min, 5 at 5 min and 9 at 10 min (umbilical cord artery pH 7.27, base excess –1.2 mmol/L).

The placenta initially detached spontaneously except to adherent areas leading to severe hemorrhage which could not be stemmed by uterine stimulants resulting in the need for a hysterectomy. The estimated overall blood loss was 3000 mL. During surgery she received 6 units of packed red blood cells and 8 units of fresh frozen plasma. Her hemoglobin level after the operation was 9.3 g/dL. After 1 day in the intensive care unit she was transferred to the obstetric ward. The patient made a steady recovery and was discharged on postoperative day 9.

The pathology report was consistent with our sonographic and MRI findings, revealing a cervical implantation of the placenta with a thin decidual layer. Beyond that placenta accreta was confirmed (Figure 2).

Figure 2

Macroscopic image of the uterus showing the implantation site of the placenta in the cervix. The cervical canal is distended by the placental tissue.

Discussion

Cervical pregnancies remain a rare implantation disorder. Cervico-isthmic pregnancies are more common as well as more lethal, because with advancing gestational age the maternal risk for massive hemorrhage increases. Our case illustrates four important points.

Owing to certain similarities cervico-isthmic pregnancies with cervical placenta can be mistaken for major placenta previa. In major placenta previa the placental implantation site is within the uterine cavum, whereas cervico-isthmic pregnancies with cervical placenta (like in our case) remain in the lower uterine segment and the cervical region. Although in placenta previa the cervical length is not affected, in cervico-isthmic pregnancies a distended cervical canal is visualized [1], which can be confused with cervical shortening.

Most cases with cervical pregnancy abort spontaneously or are terminated in early gestational age. However, in our single case experience expectant management with third trimester delivery was possible even with the shortened cervix. This is because the shortened cervix was more likely to be the result of displacement of cervical tissue than a sign of imminent premature delivery.

Implantation disorders of the placenta into the uterine wall result in placenta accreta, increta, and percreta. Probable risk factors include previous uterine surgery (i.e., curettage, Asherman’s syndrome, previous cesarean delivery) as well as in vitro fertilization. If placental growth exceeds uterine boundaries, adjacent organs (bladder, ureters, and bowel) may be damaged which might cause hemorrhage leading to the requirement of a cesarean hysterectomy [4].

In early ultrasound scans, clinical findings include visualization of products of conception in a dilated cervix. The uterus is usually of normal size. Cervical implantation in both true cervical and cervico-isthmic pregnancies may be confused with the first stage of a spontaneous abortion. Furthermore, it is important to distinguish between a true cervical pregnancy and a cervico-isthmic pregnancy so that maternal risks such as uterine rupture, hemorrhage, and hysterectomy are reduced.

From our single case experience cervico-isthmic pregnancies can be continued to the third trimester after counseling. It is important that the risk of preterm delivery as well as severe hemorrhage and organ loss is discussed with the patient.

Alternative strategies to prevent postpartum hemorrhage that have been published include uterine artery embolizations as well as ligation of the uterine or internal iliac arteries [3].

In conclusion, expectant management can be offered to patients with a cervico-isthmic pregnancy. The risk of preterm delivery for these patients is difficult to assess. In our case, the timing of delivery was dependent on the incidence of vaginal bleeding.

Furthermore, our case underlines the importance of interdisciplinary peripartum management as well as necessary skills of the delivering surgeon to control severe hemorrhage which possibly requires hysterectomy.