Caesarean scar pregnancy (CSP), sometimes known as caesarean scar ectopic pregnancy, is an uncommon but potentially significant complication of a previous caesarean section. Implantation occurs within a previous caesarean section scar in approximately 1 in 2,000 pregnancies.¹

The rate of CSP has been reported as being as high as one in 531 pregnancies among women with at least one previous caesarean section.² In New Zealand, the caesarean section rate is increasing; in 2017, 27.9% of women giving birth had a caesarean section, and just over half of these were emergency caesareans, which is an increase from 23.6% in 2008.³ Among women with at least one previous caesarean section, CSP makes up 6% of ectopic pregnancies.¹ The risk of CSP is not thought to increase with an increasing number of caesarean sections.¹

CSP implies implantation at the site of the uterine scar from a previous hysterotomy.² The diagnosis of CSP is typically made using transvaginal ultrasound. These are the New Zealand Ministry of Health’s ultrasound criteria for the diagnosis of CSP:4

1. Gestational sac that is low lying and located anteriorly or deviated towards the scar, within the lower uterus, at the level of the internal os.
2. Increased peritrophoblastic or periplacental vascularity on colour Doppler examination, and high-velocity (peak velocity >20cm/s), low impedance (pulsatility index <1) flow velocity waveforms on pulsed Doppler, in keeping with functional trophoblastic/placental circulation.
3. Negative ’sliding organs sign’, in the first trimester. This is defined as the inability to displace the gestational sac from its position at the level of the internal os using gentle pressure with the transvaginal probe.

There have been reports of CSP continuing to term, but there are significant risks of maternal morbidity and mortality if these pregnancies continue.¹ The most significant of these risks include an abnormally adherent placenta, which can result in life-threating bleeding and emergency hysterectomy.² Due to the rare nature of CSP, there is little consensus on the best approach to management, with most of the evidence available being from case reports or case series.² The Royal College of Obstetricians and Gynaecologists (RCOG) Green Top Guideline published in 2016 is based entirely on level 3–4 evidence or extrapolated from level 2+ evidence. These guidelines suggest that surgical management may be superior to medical management.⁵ Management options include conservative management, medical management with either local or systemic methotrexate (with or without potassium chloride injection) or surgical management with laparoscopy, laparotomy, hysteroscopy or hysterectomy.¹

There has been increasing interest in CSP in the literature in recent years, with a publication from Australia in June 2020 reporting on cases treated at a large tertiary centre in Brisbane (Mater Mothers’ Hospital).⁶ We present a case series from a secondary centre in regional New Zealand (Palmerston North Hospital, MidCentral District Health Board [DHB]) to examine the diagnosis, management and outcomes for women with CSP. MidCentral DHB had a mean birth rate of 2,150 births per year between 2015–2017.⁷ Between June 2015 and May 2020 there were ten women within MidCentral DHB diagnosed with CSP.

Methods

A retrospective case series was performed to identify all women treated at Palmerston North Hospital for CSP over a period of five years (June 2015 to May 2020). Patients were identified from the Gynaecology Day Unit (GDU) follow-up diaries over the relevant years.

Data were then collected from the regional patient information system. The data included demographic information, ultrasound findings, HCG levels, treatment, outcomes and complications. The outcomes and complications for each patient were also gathered from post-treatment outpatient notes.

Ultrasound images were retrospectively reviewed by a gynaecology radiologist (HL) to ensure that diagnosis was confirmed as being accurate.

Additionally, we present a single case report to highlight the journey of a single patient who required multiple treatment modalities.

Results

Nine women were treated at Palmerston North Hospital for CSP within the timeframe specified. One of these women was treated twice for two separate CSP within this time.

Baseline characteristics

The median age was 32 (IQR 30–36). The median number of previous caesarean sections was two (IQR 1–4). One woman had five previous caesarean sections. Median gravidity was five (IQR 5–7), and the median parity was four (IQR 3–4). The mean gestational age at diagnosis was six completed weeks. Median highest serum beta-HCG was 28,703 (IGR 13,439–52,671); six patients had fetal cardiac activity detected at diagnosis (60%); and three had a previous dilatation and curettage for miscarriage. Of the ten women, six identified their ethnicity as New Zealand Māori (60%), two as New Zealand European/Pākehā (20%) and two as other European (20%). There were no women who identified as Pacific, Asian or Indian among the cases of CSP.

Presentation and diagnosis

Four women presented with vaginal bleeding and abdominal pain, two women with vaginal bleeding only and three were asymptomatic at diagnosis. One woman’s presenting symptoms were not able to be identified from the documentation. This information is summarised in Table 1.

Table 1: Presenting symptoms.

The initial ultrasound report for eight of the ten cases either diagnosed CSP or indicated that appearances were suspicious for CSP. Of the two that were not detected at the initial ultrasound, one was detected at a follow-up scan a week later. The remaining case was not diagnosed until a hysteroscopy. This was performed as the woman had ongoing pain and bleeding following surgical evacuation of retained products of conception for missed miscarriage, and CSP was suspected on clinical grounds. At the hysteroscopy, the diagnosis of CSP was made and the products of conception were removed from the previous hysterotomy scar.

Treatment

Treatment varied according to clinical presentation, HCG levels, gestational age, ultrasound findings and patient preference. Women who required local injection of methotrexate were referred to the regional Maternal Fetal Medicine (MFM) service, where this was performed under ultrasound guidance. Systemic methotrexate was given at the local hospital. One woman had a spontaneous miscarriage prior to active treatment being administered. Another woman’s CSP was diagnosed at the time of hysteroscopy for retained products of conception following a presumed incomplete miscarriage. The products were removed from the previous hysterotomy scar.

Where possible, patients’ serum HCG levels were followed until they were undetectable. In some cases (eg, where hysterectomy was performed) this was unnecessary, and one patient was lost to follow-up prior to her HCG level becoming undetectable.

Table 2 provides a summary of the treatment received and the outcomes. Initial treatment was successful in seven of the ten women (70%). Of the three women whose initial treatment was unsuccessful, one had systemic methotrexate, one had locally injected methotrexate and the third had a dilatation and curettage initially for presumed missed miscarriage. Figure 1 outlines the success rates of the different initial treatments administered.

Figure 1: Initial treatment modalities and number of patients requiring further management.

Three women had local methotrexate and potassium chloride (KCl) injected into the gestational sac. One of these women (case 2) needed further treatment in the form of an emergency hysterectomy. Two women were given systemic methotrexate as primary treatment. One had a negative HCG 78 days later, and the other (case 1) required further treatment in the form of hysteroscopic resection (using a MyoSure device [Hologic]) under laparoscopic vision, with immediate resolution of HCG. Two women (cases 4 and 10) chose to have an elective hysterectomy (and bilateral salpingectomy) as their primary treatment. Case 1 had an obstetric history significant for five previous caesarean sections and had a total laparoscopic hysterectomy and bilateral salpingectomy. The procedure involved cystoscopy, ureteric stent placement and ureterolysis, due to dense adhesions on the anterior uterus that buried the uterine scar and bladder. Case 10 had one previous caesarean section and four vaginal deliveries. This woman underwent a total abdominal hysterectomy and bilateral salpingectomy without complication. One woman (case 7) was referred for local methotrexate and KCl; however, subsequent ultrasound no longer demonstrated fetal cardiac activity. The woman was offered 800mcg misoprostol in two doses two days apart. Eight days after the first does of misoprostol her symptoms were resolved and her HCG was falling appropriately. Her lowest HCG measured was 61, at 52 days following the misoprostol. We do not have any further HCG levels recorded. Interestingly, case 7 is the same woman as case 3, with a second CSP in her subsequent pregnancy. In the second CSP, this woman was treated with locally injected methotrexate and potassium chloride and did not require any further treatment. Six weeks after the methotrexate injection she was lost to follow-up, despite multiple attempts to make contact with her. Her lowest recorded HCG level was 88 on day 39 post treatment. As mentioned above, one woman (case 9) was initially treated with surgical management for a presumed missed miscarriage. This woman had ongoing bleeding prompting a repeat ultrasound, which showed 15mL of heterogenous material within the uterine cavity. She was given two doses of 800mcg misoprostol with minimal effect, then proceeded to theatre for the hysteroscopy that diagnosed the CSP. The CSP was then resected hysteroscopically (using a MyoSure device). Her HCG was negative prior to the procedure; at the time of hysteroscopy, products of conception were visualised in the caesarean scar.

Table 2: Patient characteristics and treatment modalities.

Complications

As mentioned above, case 2 required an emergency hysterectomy following local injection of methotrexate and potassium chloride. She presented acutely to the emergency department 23 days after treatment with heavy vaginal bleeding, hypotension and reduced Glasgow Coma Score (GCS). The bleeding was unable to be controlled, so she proceeded to theatre for a laparotomy and emergency hysterectomy. Her total estimated blood loss was eight litres and she was post-operatively admitted to ICU. She then made a full recovery.

Case report

We present the case of a 29-year-old woman who elected to undergo hysteroscopic resection of her caesarean section scar ectopic after unsuccessful treatment with systemic methotrexate (case 1).

The patient initially presented to the emergency department with three weeks of vaginal bleeding and lower abdominal cramping. Her medical history included severe depression and methamphetamine use. She was gravida 5 para 4 with three vaginal births; the third pregnancy was delivered by caesarean section. On admission, she was found to be pregnant with a serum HCG of 9250 mIU/mL. She was clinically stable and discharged. An outpatient ultrasound was arranged, which showed a 21x10x20mm cystic structure with echogenic rim suggestive of decidual reaction within the lower anterior uterine segment at the site of the caesarean section scar, with absence of a sliding sign (Figure 2), reported as “concerning for caesarean scar ectopic.”

Figure 2: Ultrasound findings of caesarean scar ectopic. Left: Transabdominal longitudinal view of uterus showing cystic structure with echogenic rim at level of scar. Right: Transabdominal transverse view of same structure.

The patient was seen in the Gynaecology Day Unit, and the images were reviewed by the regional Maternal Fetal Medicine unit. The patient was offered the options of systemic methotrexate or conservative management with close follow-up; she elected for treatment. Her HCG had risen (over two days) to 12,680.

The patient was observed as an outpatient. On day three post methotrexate, HCG had increased to 13,439; and on day eight post treatment it had fallen to 7,528. An ultrasound on day eight post treatment did not show any significant change from the previous scan, with the sac still present measuring 22x15x10mm. HCG continued to fall, reaching 1,608 on day 17 and 482 on day 24 post treatment.

The patient presented three times to the emergency department with ongoing pain and bleeding, and each time she was discharged with analgesia and ongoing outpatient follow-up. A further ultrasound was arranged on day 30 post treatment, which showed a slight increase in the size of the sac: it then measured 22x17x30mm, with ongoing vascularity on doppler imaging. HCG levels continued to drop, reaching 79 on day 36 and 46 on day 41. The case was reviewed at a departmental gynaecology meeting and a decision was made to offer surgical management. The patient initially was uncertain about surgery but eventually agreed. A hysteroscopic approach under laparoscopic vision was chosen.

Eleven weeks afer the methotrexate treatment, the patient was admitted for surgical management. Under laparoscopic vision, a hysteroscope was inserted into the uterus (Figure 3). The region of the caesarean scar was extremely thin but intact (Figure 4). The ectopic pregnancy tissue was resected hysteroscopically using a MyoSure XL device (Hologic). The myometrium remained intact as evidenced laparoscopically. Bleeding was minimal throughout the procedure.

Figure 3: Hysteroscopic view of caesarean scar ectopic pregnancy. Left: Pregnancy tissue on the anterior wall of the uterus. Right: Resection of the tissue using MyoSure device.

Figure 4: Laparoscopic observation of hysteroscopic resection of caesarean scar ectopic pregnancy. Top: Laparoscopic view of hysteroscopic light source demonstrating how thin the myometrium was, but that it remained intact. Bottom: Post-resection review of thin myometrium at the level of the caesarean section scar.

The patient was admitted overnight, and the following morning her HCG was two. She was discharged home, and one week following surgery her HCG was <1. Histology confirmed products of conception.

Discussion

We report a series of ten cases of caesarean scar pregnancies in a regional centre in New Zealand. The presentation, diagnosis, management and complication rate of these cases were similar to those reported elsewhere.^2,6,8–10 The majority of cases were diagnosed by ultrasound prior to management, but one was not diagnosed prior to surgical management. More than two thirds of women were successfully treated with primary management, with one third requiring multiple treatment modalities. We report one severe life-threatening haemorrhage and three cases resulting in hysterectomy. We also show a disproportionate number of Māori women presenting with CSP. We present a single case to highlight the potential complexity and prolonged course that management of CSP can entail.

As the caesarean section rate continues to increase^3,7 we may see more women with CSP. It is therefore important that, even in smaller centres, clinicians are familiar with the diagnostic and management challenges associated with CSP. There is little consensus in international guidelines as to the optimal management of CSP. The RCOG guideline on the diagnosis and management of ectopic pregnancy published in 2016⁵ makes recommendations based on low-quality evidence. The NICE guideline published in 2019 on the diagnosis and initial management of ectopic pregnancy and miscarriage does not mention CSP.¹¹ As the potential for morbidity and mortality is very high with CSP, it is important to develop consistent guidelines to facilitate early and accurate diagnosis and guide optimal management. Our case series, similar to previously reported experiences,^2,6,8–10 shows that, although the majority of cases were diagnosed sonographically prior to management, one case was not diagnosed until after treatment had been initiated; this scenario may result in significant and potentially avoidable morbidity.

The diagnosis and management of CSP should involve a multidisciplinary approach including specialist radiologists and MFM teams. The rarity of CSP, especially in regional centres, results in limited expertise and experience among clinicians providing care for these women. In smaller centres such as Palmerston North, it may be beneficial to have a dedicated radiologist with a special interest in gynaecological ultrasound. It is also important to involve the regional MFM team in order to maximise the accuracy and consistency in diagnosis and management.

Our case series has shown that there is a variable approach to management of CSP in Palmerston North Hospital, in keeping with treatment described in recent literature.^2,5,6 Because New Zealand has a relatively small population with relatively small numbers of CSP, it would be useful to collate a national database of cases. This could then be used to develop a national protocol for the diagnosis and management of CSP.

This case series illustrates that Palmerston North Hospital has a rate of CSP comparable to that expected from prior studies. For example, the tertiary centre in Australia where the 2020 study was conducted (Mater Mothers’ Hospital, Brisbane) had a birth rate of approximately 6,000–7,000 births per year¹² and reported 28 cases of CSP over five years. MidCentral DHB has a birth rate of 2,150 births per year and reported ten cases over five years.

In New Zealand, the rate of caesarean section among Māori women is just over 20%, and for European/other ethnicities (excluding Asian, Indian and Pacific) it is approximately 28%.³ In MidCentral DHB, 18% of women having caesarean sections are Māori, 23% are New Zealand European and 29% belong to other ethnicities (excluding Pacific, Indian and Asian).⁷ The population of MidCentral DHB is 20.2% Māori.¹³ Based on these statistics, while the rate of caesarean section among Māori women is in-line with the proportion of the population that identify as Māori, the rate of CSP is three times that which would be expected. The significance of this is difficult to comment on given the small sample size presented here. Again, a national database would provide further insight to determine whether this represents a true inequity based on ethnicity.

We present a series of ten cases of caesarean scar pregnancy, demonstrating similar challenges in regional New Zealand to those reported elsewhere. Although the diagnosis is most often made sonographically, cases where the diagnosis is missed are at risk of inappropriate management and serious morbidity. Management is heterogeneous, and although there is little guidance from the literature, primary management was successful in seven out of ten cases in this series. CSP can result in serious morbidity with major haemorrhage and hysterectomy. We report a disproportionately high number of cases in Māori women. Our results would support the creation of a national register for caesarean scar pregnancy to improve diagnosis and management across New Zealand.