Ectopic pregnancy (EP) is an early pregnancy complication characterized by the implantation of an embryo outside of the normal endometrial cavity and is potentially life-threatening.[1] It occurs in around 1-2% of all pregnancies and is a significant contributor to maternal morbidity and mortality, especially in cases where it is not diagnosed in time and tubal rupture follows.[2] The fallopian tube is the most common place for an ectopic pregnancy, but it can also occur at other uncommon sites, such as the ovary, cervix, interstitial portion of the fallopian tube, abdomen, and previous cesarean section scar.[3] The anatomical site of implantation is of importance in clinical practice as it can have different imaging features, be a diagnostic challenge, and demand a new management approach in the case of atypical ectopic pregnancy.[4]

Cesarean scar pregnancy (CSP) is an ectopic pregnancy in which the gestational sac partially or completely buries itself in the scar from a previous cesarean delivery, and has become especially noteworthy because of the rising rate of cesarean delivery.[5] In modern times, it is suggested that cesarean scar pregnancy affects around 0.2-0.5% of women who have previously had a cesarean section. An earlier report estimated the incidence at around 1 in 1,800-2,216 pregnancies; while among women who have both an ectopic pregnancy and a previous cesarean delivery, the incidence of CSP has been estimated at 6%.[6-8] Importantly, the trend of increasing recognition of CSP is a global phenomenon that mirrors the global rise in cesarean delivery rates; one recent review reported that, over the last decades, cesarean delivery rates have risen significantly, which has led to a greater population at risk of scar implantation.[9]

Previous cesarean delivery not only could affect the risk of scar pregnancy but may also affect the location of subsequent ectopic pregnancy.[3] Surgery on the uterine wall can leave a scar defect or niche where an embryo may implant, causing a pregnancy in or near the cesarean scar.[10] CSP is clinically significant because delayed diagnosis may lead to massive bleeding, uterine rupture, placenta accreta spectrum, hysterectomy, and infertility.[11] Recent studies have highlighted the importance of early transvaginal ultrasound to detect the exact location of the gestational sac and features like the location of the gestational sac and thickness of the residual myometrium.[12-14] While tubal pregnancy remains the most common form of ectopic pregnancy, there is evidence that the location of tubal implantation is not constant. A large study of 3,915 ectopic pregnancies showed that 84.7% were tubal pregnancies, 8.63% were cesarean scar pregnancies, and the number of pregnancies that were cesarean scar pregnancies showed a significant increase over time.[15]

Recognition of the anatomic location of ectopic pregnancy has important implications for early diagnosis, focused ultrasonographic evaluation, early management, and avoidance of serious maternal complications, as well as the increasing rates of cesarean delivery and the growing awareness of cesarean scar and other non-tubal ectopic pregnancies. The association of this has, however, not been examined specifically in our population and is limited there. Hence, the current study was conducted to investigate the relationship between the prior cesarean section and the site of ectopic pregnancy. Therefore, the present study was conducted to understand the relationship between the site of ectopic pregnancy and previous cesarean section.

The study was conducted as an analytical cross sectional on hospital based at Haripur International Hospital in the Department of Obstetrics and Gynecology. The period was six months, from 1st January, 2026 to 30th June, 2026. A sample size was determined from the OpenEpi online sample size calculator for the estimation of a single proportion. The expected proportion was a cesarean scar pregnancy rate of 6.1%, as reported before, among women who had at least one previous cesarean delivery and had an ectopic pregnancy.[7] The sample size was calculated at a 95% confidence level, with an absolute precision of 3%; the minimum calculated sample size was approximately 246 participants. To make up for incomplete records, some women were not found or did not report during data collection, and 10% was added to the final sample of 271 women with ectopic pregnancy. Non-probability consecutive sampling was used. All women who appeared and met the pre-specified inclusion criteria were consecutively recruited until the sample size was met. Women of reproductive age (18 years or older) with a confirmed ectopic pregnancy during the study were included. The diagnosis of ectopic pregnancy was made based on transvaginal ultrasonography, serum β-hCG level, operating room findings, and/or histopathology, when applicable. Patients with and without previous cesarean delivery were both included to determine the association between previous cesarean delivery and ectopic implantation site. Those who had previously had a cesarean delivery were also divided based on the number of previous cesarean deliveries. Women who had heterotopic pregnancy, pregnancy of unknown location without definite diagnosis of ectopic pregnancy, incomplete medical records, and women with unknown anatomical location of the pregnancy were excluded. Post-cesarean women with major uterine surgery (including extensive myomectomy or reconstructive uterine surgery) were also excluded if this surgical procedure could have affected the anatomical site of pregnancy. Those patients who refused to participate were not included in the study. Following informed written consent, the following information was collected using a structured data collection questionnaire including demographic information, obstetric information, clinical information, ultrasonographic information, laboratory information and operative information. Demographic data comprised age, place of residence, and body mass index (BMI) as available. Obstetric factors were gravidity, parity, history of abortion, number of previous cesarean deliveries, time to last cesarean delivery, and previous ectopic pregnancy. Clinical parameters that were evaluated were: gestational age at presentation, presenting symptoms, vaginal bleeding, abdominal/pelvic pain, hemodynamic status, and serum β-hCG level. Data about prior cesarean section were from the patient's medical records and corroborated from the obstetric history where possible. Transvaginal ultrasonography performed by an experienced obstetrician/radiologist was used to determine the anatomical location of ectopic pregnancy, the main method used. Ectopic pregnancies were classified based on the site of implantation: tubal, cesarean scar, cervical, ovarian, abdominal, interstitial/cornual, and other documented sites. The diagnosis of cesarean scar pregnancy was made when the gestational sac was found at the site of the previous cesarean scar with an empty uterine cavity and other supporting sonographic features such as prominent peritrophoblastic vascularity, thin or absent myometrium between the sac and the urinary bladder, and a negative sliding-organ sign, according to the previously established criteria. Surgical management was performed to confirm or complement the diagnosis, and the findings were analysed with the histopathological report. All information was collected anonymously, and each person in the study had a separate identification number. The data was entered, coded, and analyzed with IBM SPSS Statistics, version 26. The Shapiro-Wilk test was used to test continuous variables for normality. Continuous variables were presented as mean ± SD and median with interquartile range for non-normally distributed variables. Categorical variables were summarized in the form of frequencies and percentages. The main exposure was previous cesarean delivery, which was classified into either no or yes; the main outcome was the anatomical site of ectopic pregnancy. The association between previous cesarean delivery and ectopic pregnancy location was assessed using the chi-square test and Fisher's exact test. The independent-samples t-test and Mann-Whitney U test was used to compare continuous variables between two groups. Stratification was done on the basis of the following potential effect modifiers: age, parity, number of cesarean deliveries in the past, and gestational age. A multivariate logistic regression was performed to determine the independent association of previous cesarean delivery with ectopic pregnancy location after adjustment for potential confounding factors. Odds ratios and 95% confidence intervals were presented. A p-value <0.05 was considered statistically significant.

A total of 271 women were included who had a confirmed ectopic pregnancy. The mean age of the patients was 29.8 ± 5.6 years, and the median gestational age at presentation was 7.0 (6.0-8.0) weeks. The cesarean delivery rate among the participants was reported in 112 (41.3%) and hemodynamic instability occurred in 38 (14.0%) cases (Table 1).

Women who had delivered by cesarean had significantly higher gravidity and parity and were older than those who had not delivered by cesarean. There were no significant differences seen in terms of previous abortion or previous ectopic pregnancy (Table 2).

The clinical manifestations and signs at presentation were similar in both groups. The most common presenting symptoms were abdominal/pelvic pain and vaginal bleeding with no significant difference in hemodynamic instability, gestational age, or serum β-hCG level between those with prior cesarean delivery and those without. (Table 3)

The most common anatomical presentation was tubal ectopic pregnancy, with cesarean scar pregnancy being the second most common presentation. Ovarian, cervical, interstitial/cornual, and abdominal pregnancies were relatively rare cases of implantation sites (Table 4).

Previous cesarean delivery was found to be associated with the location of the ectopic pregnancy, which was statistically significant (p<0.001). The only difference between the two groups was that cesarean scar pregnancy was seen only in women who had undergone cesarean delivery; tubal pregnancy was the commonest site of pregnancy in both groups (Table 5).

Women with non-tubal ectopic pregnancy were significantly older and higher gravidity and parity than those with tubal ectopic pregnancy. In addition, women with non-tubal ectopic pregnancy were more likely to have prior cesarean delivery than were women with IUP (p=0.005).(Table 6)

In women who have had a previous cesarean delivery (CD), women who had two or more previous CD were more likely to have a cesarean scar pregnancy than those who had one CD (Table 7) and this difference was statistically significant (p=0.048).

The relationship between history of previous cesarean delivery and non-tubal ectopic pregnancy was strongest among women under 30 years of age and those who presented at or before 7 weeks of gestation (Table 8).

In multivariable logistic regression analysis, after adjustment for age, BMI, previous tubal ectopic pregnancy, gravidity, parity, and gestational age, the risk of non-tubal ectopic pregnancy remained significantly increased in women who had had a previous cesarean delivery (Table 9).

Table 1. Demographic and clinical characteristics of study participants (n=271)

Table 2. Obstetric characteristics according to previous cesarean delivery

Table 3. Presenting clinical characteristics according to previous cesarean delivery

Table 4. Anatomical location of ectopic pregnancy (n=271)

Table 5. Association between previous cesarean delivery and anatomical location of ectopic pregnancy

Table 6. Comparison of women with tubal versus non-tubal ectopic pregnancy

Table 7. Anatomical location according to number of previous cesarean deliveries

Table 8. Stratified analysis of association between previous cesarean delivery and non-tubal ectopic pregnancy

Table 9. Multivariable logistic regression analysis for non-tubal ectopic pregnancy

In the present study, a previous cesarean delivery was associated with the site of ectopic pregnancy. A previous cesarean history was found in 41.3% of 271 women with ectopic pregnancy and 100% of women with a previous cesarean history had cesarean scar pregnancy. Furthermore, age, BMI, gravidity, parity, previous ectopic pregnancy, and gestational age were independently associated with non-tubal ectopic pregnancy after adjustment for previous cesarean delivery (p=0.032). These results are consistent with the hypothesis that the site of the previous uterine surgery may affect the site of the next pregnancy and that it is essential to recognize the possibility of an atypical ectopic pregnancy in women who have previously had cesarean surgery. The majority of our sample (85.2%) were tubal ectopic, and cesarean scar pregnancy was the commonest non-tubal type of ectopic pregnancy (7.4%), consistent with the known epidemiological pattern of ectopic pregnancy. This is of clinical significance because an increasing number of recent publications have noted that cesarean scar pregnancy is a separate entity from ectopic pregnancy and not just an uncommon site. In 2022, Jurkovic et al. pointed out that cesarean scar pregnancy should be considered as an ectopic pregnancy since it is a process that takes place outside the normal endometrial cavity and poses a high risk to the mother.[16] The finding that cesarean scar pregnancy occurred only in women who had previous cesarean delivery was biologically plausible and in agreement with studies reporting on the implantation within a previous uterine scar. In 2021, Meng et al. reviewed 71 cesarean scar pregnancies and found that a history of a cesarean section was a critical clinical feature, and a diagnosis was made when a previous cesarean section and transvaginal ultrasonographic evidence of implantation at the cesarean section scar were found.[17] Likewise, Heidar et al. presented cesarean scar pregnancy as a potentially life-threatening ectopic pregnancy and highlighted its association with previous cesarean section.[18] The 7.4% proportion of cesarean scar pregnancy among all ectopic pregnancies was also similar to the approximately 6% that is often cited among women who have had cesarean delivery. In a 2022 retrospective study in the Czech Republic, cesarean scar pregnancy was estimated to be about 6% of all ectopic pregnancies in women who had previously had a cesarean section.[19] A higher percentage in our population might be due to different patterns of referral, different rates of cesarean delivery, variations in diagnostic practices and the availability of early transvaginal ultrasound, as well as the fact that our population included a hospital-based population. One of the key findings of our study was that women with a history of 2 or more cesarean sections had a higher prevalence of cesarean scar pregnancy. A case of cesarean scar pregnancy was found in 28.2% of women who had undergone two or more cesareans as opposed to 12.3% of women who had undergone one cesarean delivery (p=0.048). Recent evidence was strong for this finding. Kidera et al. (2026) found that having two or more previous cesarean sections was significantly associated with cesarean scar pregnancy in multivariable analysis (p=0.006). Their study also indicated that there should be a greater level of clinical suspicion for scar implantation if a patient has had more than 2 cesarean sections.[20] In a similar study, a multicenter study on reproductive outcomes following cesarean scar pregnancy in 2025 showed that scar pregnancy recurrence was associated with the number of cesarean sections.[21] The finding of younger age of women with non-tubal ectopic pregnancy than those with tubal ectopic pregnancy and higher gravidity and parity of the former was also consistent with recent CSP literature. Gluska et al. (2025) made a comparison of cervical and cesarean scar pregnancies in 899 ectopic pregnancies and found that women who developed cesarean scar pregnancy had higher gravidity, parity, and a higher number of previous cesarean deliveries.[22] Likewise, the Saudi Arabian study by Al-Qassim investigators concluded that parity was an important factor associated with scar-site pregnancy, and hence the relationship between increasing reproductive history and abnormal implantation at the cesarean scar.[23] In our study, there was no significant difference in clinical presentation, gestational age and serum β-hCG between women with scar implantation and those with other ectopic pregnancy locations, indicating that clinical presentation alone may not reliably differentiate scar implantation from other ectopic locations. The fact that this has been found further illustrates the need to assess the anatomy rather than relying on symptoms or biochemical markers - this should be done using transvaginal ultrasonography. The serum level of β-hCG was significantly higher in cesarean scar pregnancy than in tubal and other ectopic pregnancies, but clinical history and imaging continued to play an important role in early diagnosis, as reported by Kidera et al. (2026).[20] Our results also have implications for the practice of early diagnosis. Cesarean scar pregnancy has been reported exclusively in women who have had a previous cesarean delivery; thus, the previous cesarean history should be considered specifically in the initial evaluation of women with suspected ectopic pregnancy. In early first trimester ultrasound screening, a 2024 clinical opinion suggested that women with prior cesarean delivery should have systematic sonographic assessment to prevent severe hemorrhage and other complications, as early diagnosis of cesarean scar pregnancy might be helpful.[24] In a 2024 retrospective study all cases of cesarean scar ectopic pregnancies were found to be diagnosed by transvaginal ultrasound (TVUS), and 2/3 of the women with cesarean scar ectopic pregnancies had had more than one previous cesarean section.[25] In conclusion, the present study showed that cesarean scar and other non-tubal implantation were significantly associated with previous cesarean delivery. The results are in keeping with the latest literature and highlight the importance of performing careful early transvaginal ultrasonographic assessment of women who have a history of cesarean delivery. Early recognition of the site of implantation may help to timely manage these patients on an individual basis and thus avoid the severe maternal morbidity associated with delayed diagnosis. LIMITATIONS There were a number of limitations to the study. The cross-sectional design of its hospital based study did not allow for the identification of a causal association between the location of ectopic pregnancy and prior cesarean delivery. Non-probability consecutive sampling may result in selection bias and may not allow for the results to be generalized to the population. The limited size of the non-tubal ectopic pregnancy group, especially the small number of very uncommon implantation sites, limited the statistical power of the subgroup analyses. Details on previous cesarean sections and other obstetric characteristics were in part based on medical records and participant recall and hence could have led to information bias. In addition, the study was performed at one center and multicenter studies with larger sample sizes are required to confirm these results.

Anatomical location of ectopic pregnancy was significantly related to previous cesarean delivery. The incidence of cesarean scar pregnancy was observed only in women who had had a previous cesarean delivery and was higher among women who had more than one previous cesarean delivery. After adjusting for potential confounding factors, previous cesarean delivery was also independently associated with non-tubal ectopic pregnancy. The results of this study underscore the need for a detailed cesarean history and careful early transvaginal ultrasonographic evaluation for recognizing uncommon implantation sites and expedient management.