Main findings
Our study found that a large proportion of CSP cases (41.5%) were undiagnosed as CSP but were diagnosed as normal pregnancies or abortions at the first contact with healthcare providers. The only significant risk factor for undiagnosed CSP was the first point of care at a primary or secondary level hospital. Undiagnosed cases had higher rates of serious complications and post-surgery anemia, stayed longer in hospital, and had higher cost than diagnosed cases.
Strengths and limitations
To our knowledge, this is the first study that explored risk factors of undiagnosed CSP at the first contact of healthcare providers and compared outcomes between undiagnosed CSP cases and diagnosed CSP cases [
1,
5,
6,
8‐
21]. The study population included all CSP cases who were treated in the catchment area, therefore, there was no selection bias. This study is also one of the largest in the field [
1,
5,
6,
8‐
21]. The final diagnosis of CSP was valid and solid, and the chance of misclassification at the final diagnosis was unlikely. We analyzed risk factors for undiagnosed CSP cases from both the patient and healthcare provider perspective, which helps to interpret the results and compare with previous studies.
The maternity care team of the only tertiary maternity care hospital in Qingyuan region is experienced in treating high-risk pregnancies, which ensured that no death occurred in the CSP cases during the study period. However, serious complications such as placenta accreta, placenta previa, uterine rupture, and heavy bleeding did occur in CSP cases who were undiagnosed at the first contact with healthcare providers, and two such cases were in “near miss”.
We used post-surgical anemia to serve as an indicator of the severity and complexity of the patient’s condition. Data on laboratory-diagnosed anemia from medical charts are reliable. In this study, more than 28% of women with undiagnosed CSP developed post-surgical anemia, while only 7% with diagnosed CSP. Moreover, undiagnosed CSP cases had longer hospital stays and higher cost than diagnosed cases, indicating that undiagnosed CSP not only affects the patient’s health, but also imposes a burden on the health care system. However, sample size of this study may be limited to assess smaller effects. Some factors such as gestational age at the first contact with healthcare providers may become significant if a larger study sample is available. The data did not have information on previous pregnancies such as quality and healing process of previous cesarean section, which prevented us from in-depth investigation of the causes for failure to a timely diagnosis of CSP.
Interpretation
The rate of CSP in this study was in the high end among previous studies [
4‐
6]. This is not a surprise given the historically high cesarean section rate [
2] and the recent change in second-child policy in China [
7]. Most previous studies in this field described clinical features of CSP cases only [
1,
5,
6,
8‐
21], with no attempt to examine risk factors for undiagnosed CSP at initial contact with healthcare providers. Risk of CSP appears to be increased with the number of cesareans, history of dilatation and curettage, placental pathology, history of ectopic pregnancy, and use of assisted reproductive technology such as IVF [
4]. Although the importance of timely diagnosis for CSP has been discussed in these studies [
1,
5,
6,
8‐
21], risk factors for failure to make a timely diagnosis have not been assessed.
Risk factors for CSP are different from risk factors for undiagnosed CSP. Our study suggests that for diagnosis, risk factors from healthcare providers may be more important than those from patients, because patient’s characteristics (e.g. age, parity, rural residence, and gestational age) were not statistically significantly associated with diagnosis, while the level of health care facility was. We should emphasize that, in this study, undiagnosed CSP refers to the diagnosis at patient’s first contact with a healthcare provider - eventually all CSP cases were diagnosed accurately. Delaying in diagnosis contributes greatly to adverse outcomes. If a diagnosis of normal pregnancy is made at the initial visit, pregnancy may continue and lead to serious conditions such as placenta accreta or placenta previa. As in other aspects of health care and in other parts of China [
23,
24], huge variations in terms of competence of health care providers and facilities in maternity care exist in Qingyuan. Primary care is mostly provided by township hospitals and secondary care is mostly provided by county hospitals. In these primary and secondary care facilities, medical workers, including both sonographers and physicians, often lack relevant CSP knowledge to make an accurate diagnosis [
25]. Furthermore, these hospitals have no vaginal ultrasound or color Doppler and only have abdominal ultrasound. Abdominal assessment lacks resolution, particularly in early pregnancy and may not have an accurate diagnosis. It is, therefore, crucial to ensure that medical staff at these hospitals take carefully medical histories including cesarean section and vaginal bleeding and transfer patients with a suspected CSP to tertiary care centers for further assessment.
We searched Medline with key words of “Cesarean Scar Pregnancy AND Diagnosis”, and identified one case report that described a CSP that was initially diagnosed as another condition despite using ultrasound [
21]. This report emphasizes the need for formal training of staff in all maternal care centers. Transvaginal ultrasound examination has advantages of being easy to operate, repeatable, and low cost, and should be the first choice. Diagnosis of CSP by vaginal ultrasonographic examination could be established as follows: 1) uterus is slightly enlarged, 2) there is no pregnancy in uterine cavity, 3) endometrial line is clearly visible, 4) a gestational sac with a york sac or crown length with or without heart rate, or complex mass with mixed echogenicity is located in the myometrium at the level of lower uterine segment, and is surrounded by visible blood flow, and 5) muscular layer between gestational sac and bladder is thin [
3‐
6,
26‐
30]. Any pregnant woman with a history of cesarean section should be evaluated for CSP, using a thorough ultrasound assessment. For pregnant women with a history of cesarean section and vaginal bleeding, blind suction or curettage is dangerous.