https://orcid.org/0000-0001-6164-019X
Figures
Abstract
Background
Increased uterine artery resistance in pregnant women with a history of cesarean section has been suggested to contribute to adverse pregnancy outcomes. However, the literature presents conflicting reports on this association. In this comparative meta-analysis and systematic review, we aimed to evaluate the studies that reported uterine artery resistance using Color Doppler ultrasonography in pregnant women with and without a history of cesarean section.
Methods
We searched PubMed, Scopus, Web of Science, and Embase up to April 2024 using relevant keywords. Study selection was performed by two independent researchers, with conflicts resolved by a third. Risk of bias was assessed using the Newcastle-Ottawa Scale. The primary outcomes were the Pulsatility Index (PI) and Resistance Index (RI) Meta-analysis and meta-regression were conducted using STATA version 17.
Results
After screening 442 articles, the meta-analysis included six studies, encompassing 1,656 participants. We found a small but statistically significant increase in uterine artery resistance, based on PI, in women with a history of cesarean section (Hedges’s g = 0.15, 95% CI [0.03, 0.26], p = 0.01). Heterogeneity among studies was low (I² = 26.60%, p = 0.23), and no significant publication bias was detected (Egger’s test, p = 0.81). Analysis of the RI, based on two studies, showed a non-significant increase in the cesarean group (Hedges’s g = 0.19, 95% CI [−0.06, 0.43], p = 0.13).
Conclusion
A history of cesarean section may be associated with increased uterine artery resistance. These findings suggest a possible benefit in monitoring uterine artery resistance in subsequent pregnancies, mainly using Color Doppler ultrasonography, to better understand potential risks such as preeclampsia and intrauterine growth restriction. However, given the limited evidence, further studies are warranted to confirm these associations and clarify their clinical relevance.
Citation: Mohazzab A, Mohammadzadeh A, Nikfar B, Masoumi S, Shoraka E, Hashemi N, et al. (2025) A comparative systematic review and meta-analysis of uterine artery resistance in pregnant women with and without previous history of cesarean section. PLoS One 20(6): e0325352. https://doi.org/10.1371/journal.pone.0325352
Editor: Mohammad Haddadi, Tehran University of Medical Sciences, IRAN, ISLAMIC REPUBLIC OF
Received: October 24, 2024; Accepted: May 12, 2025; Published: June 18, 2025
Copyright: © 2025 Mohazzab et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: All relevant data are within the manuscript and its Supporting Information files.
Funding: The author(s) received no specific funding for this work.
Competing interests: The authors have declared that no competing interests exist.
Introduction
Cesarean section rates have been increasing globally, resulting in a rising number of women with uterine scars from previous cesarean deliveries [1]. The necessity of assessing complications and side effects of cesarean sections is crucial due to the significant impact they can have on maternal and fetal health. Cesarean sections can lead to several short-term complications, such as infection, hemorrhage, and anesthesia-related issues, as well as long-term complications affecting subsequent pregnancies, including uterine rupture, abnormal placentation, and increased risk of preterm birth [2–4]. These complications not only pose risks to maternal health but can also result in adverse neonatal outcomes such as low birth weight and respiratory distress [5,6].
However, the literature presents conflicting reports on this association. Some studies have found a positive correlation, indicating increased uterine artery resistance in women with previous cesarean sections [7,8], even if the differences were not statistically significant [9]. Conversely, other studies have found no significant differences or negative correlations [10,11].
Several theories have been proposed to explain this association. First, it is hypothesized that the uterine scar tissue resulting from a Cesarean section may lead to impaired vascular remodeling. This process is crucial during early pregnancy to ensure adequate blood flow to the placenta [12,13]. The scar may cause fibrosis and localized ischemia, reducing the elasticity of the uterine wall and increasing vascular resistance [14]. Another explanation proposed using animal studies is poor trophoblastic invasion, a process essential for establishing a healthy placental blood supply, which may be disrupted by cesarean-induced uterine scarring [15,16].
Based on the existing literature, we hypothesized that uterine artery resistance—particularly as measured by the Pulsatility Index (PI)—would be significantly higher in pregnant women with a history of cesarean section compared to those without. This hypothesis stems from studies suggesting impaired vascular remodellingand altered uteroplacental perfusion in scarred uteri. Clinically, identifying such associations could inform obstetric monitoring strategies, especially in high-risk pregnancies.
Methods
PECO for primary research question
We formulated the study question using the PECO framework [17] (Population, Exposure, Comparator, Outcome) as follows: Is a history of cesarean section associated with increased uterine artery resistance—measured by PI or RI—in subsequent pregnancies compared to women without such a history? Where Population (P): Pregnant women undergoing second-trimester Doppler ultrasound assessment; Exposure (E): History of previous cesarean section; Comparator (C): Women with no prior cesarean section; Outcome (O): Uterine artery resistance indices, including Pulsatility Index (PI) and Resistance Index (RI), assessed using color Doppler ultrasonography.
Eligibility criteria
This systematic review was conducted according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) standards [18] and registered in Prospective Register of Systematic Reviews (PROSPERO) (CRD42024524343). We included all peer-reviewed original observational and interventional studies conducted in humans, as well as relevant academic theses (both published and unpublished) and full-text conference papers, provided they reported on uterine artery resistance measured by color Doppler ultrasonography in healthy pregnant women with and without a history of cesarean section. Eligible studies could be in any language, provided sufficient methodological and outcome data were accessible.
Studies were excluded if they lacked a comparison between women with and without prior cesarean section, did not report uterine artery resistance indices (PI or RI), provided insufficient data for analysis, or were non-original publications such as reviews, case reports, or abstracts without full texts.
Information sources and search strategy
The databases PubMed, Scopus, Web of Science, and Embase were systematically searched for studies up to 6th April 2024. The authors concurred that Cesarean, Caesarean, “abdominal delivery”, Doppler, “Uterine artery” and UtA be in the search query. Literature search was conducted in the title and abstract by mentioned search terms. The search strategy was tailored for each database to capture the most relevant studies (See S1 Table).
Study selection
Two independent authors (Az.M and B.N) reviewed the title, abstract, and full text of retrieved studies after identifying and deleting duplicates by EndNote software version X8(Clarivate Analytics, Philadelphia, PA, USA). A third researcher (Ar.M) was consulted to resolve the conflict. Studies were included in the analysis if they reported Color Doppler ultrasonography results for uterine artery resistance in both patients with and without a history of cesarean section, either in the abstract or full text. To access non-English or unavailable studies, we email authors and journals [19–24].
Risk of bias (ROB) and certainty assessment
All selected articles were assessed for the ROB using the Newcastle-Ottawa (NOS) checklist for observational studies [25]. Study quality was categorized into Good quality, Fair quality, and Poor quality based on the NOS checklist instruction. This tool evaluates three domains: A: Selection (up to 4 stars): Representativeness of the exposed cohort, selection of the non-exposed cohort, ascertainment of exposure, and confirmation that the outcome was not present at study start. B: Comparability (up to 2 stars): Assessment of whether the study controlled for confounding variables. C: Outcome (up to 3 stars): Assessment of outcome, adequacy of follow-up, and length of follow-up sufficient for outcomes to occur.
Two reviewers (Ar.M and Az.M) independently assigned stars to each item using a standardized NOS form. Disagreements were resolved through discussion or consultation with a third reviewer (Sh.Ch). Based on the total score out of 9 stars, studies were categorized as:Good quality (7–9 stars), Fair quality (4–6 stars), Poor quality (0–3 stars). All included studies scored 7 or higher and were rated as “Good” quality.
The certainty of evidence for each outcome was assessed using the GRADE (Grading of Recommendations, Assessment, Development and Evaluation) approach [26] b (Ar M). He performed both a manual GRADE assessment based on GRADE guidelines and a software-supported evaluation using GRADEpro GDT (https://gradepro.org). The manual assessment was used to provide contextual judgments for domains such as imprecision and inconsistency, particularly in interpreting clinical relevance and methodological consistency across studies.
Summary measures
The PI and RI (Resistance Index) were considered the study outcomes and extracted from the papers. PI is a Doppler ultrasound measurement that reflects the pulsatility of blood flow, calculated as: PI = (Peak Systolic Velocity − End Diastolic Velocity)/ Mean Velocity. RI, also known as the Pourcelot index, is calculated as: RI = (Peak Systolic Velocity − End Diastolic Velocity)/ Peak Systolic Velocity [27]
Data extraction
The author’s name, publication years, age, Body Mass Index (BMI), Doppler week, PI, and RI were other variables extracted from the eligible studies and imported into the Excel database by two authors (B.N and E.S) independently and the discrepancy was dissolved by (Ar.M).
Statistical method
Meta-analysis was conducted using STATA version 17 (StataCorp LLC, College Station, TX, USA) to synthesize data from the included studies. Each study’s primary outcomes, including the PI and Resistance Index (RI), were extracted. We employed a random-effects model, specifically the DerSimonian-Laird method, to account for potential heterogeneity among studies. Hedges’s g was calculated to measure the effect size, which estimates the standardized mean difference between the groups (women with and without a history of cesarean section).
Heterogeneity among the studies was assessed using the I² statistic, which describes the percentage of total variation across studies that is due to heterogeneity rather than chance. An I² value greater than 50% indicates substantial heterogeneity. Additionally, Cochran’s Q test was used to test for heterogeneity. Potential publication bias was assessed using Egger’s regression test. Given the small number of included studies, we supplemented Egger’s regression test with visual inspection of funnel plots for each meta-analysis outcome, in accordance with PRISMA recommendations. A non-significant p-value (p > 0.05) in Egger’s test suggests that there is no significant publication bias.
Meta-regression and additional analyses
Meta-regression was performed to explore the influence of potential confounders on the observed effect sizes. This included variables such as gestational age at the time of Doppler assessment, maternal age, and BMI. Sensitivity analyses were also conducted by excluding studies that are the source of the heterogeneity to assess the robustness of the findings.
Mean and standard deviation calculation using MoM
Since some studies reported the mean and standard deviation for the multiples of the median (MoM) of the PI, we generated simulated datasets reflecting the MoM distribution adjusted for gestational age using Gomez et al.‘s reference values to estimate the mean and standard deviation of the PI values [28]. This Bayesian simulation process involved adjusting the MoM values for gestational age through regression analysis and summarizing the simulated PI values. The results from 2,000 simulations provided robust estimates for the mean and standard deviation of the PI, adjusted for gestational age.
Results
A total of 958 records were identified through database searches, and one additional record was identified through other sources. After removing duplicates, 441 records were screened by title and abstract. Of these, 67 full-text articles were assessed for eligibility, and 61 were excluded with reasons. Ultimately, six studies met the inclusion criteria and were included in the final analysis. One of the included studies was conducted by our research team. Although we were aware of its findings during the review process, we followed a rigorous, predefined eligibility protocol and objective data extraction procedures to minimize bias.
The six included studies were published between 2011 and 2023 and originated from Turkey (n = 3), Iran (n = 1), Thailand (n = 1), and Norway (n = 1). All studies employed observational designs—either retrospective or prospective cohort studies. Collectively, they encompassed a total of 1,656 pregnant women, with individual study sample sizes ranging from 64 to 503. Uterine artery resistance was assessed using Doppler ultrasound, and outcomes were reported as either PI, RI, or both. All studies used standard gestational windows (11–32 weeks) for Doppler measurements. (Fig 1, Table 1). The PRISMA flowchart illustrates the stringent selection process employed to ensure the inclusion of high-quality studies in our analysis. All six studies included in the meta-analysis were assessed for quality using an NOS checklist and were rated as “Good” based on their selection, comparability, and outcome criteria. (Table 2). The certainty of evidence for each outcome was assessed using the GRADE approach, both manually and through the GRADEpro GDT software (https://gradepro.org). For the association between prior cesarean section and increased uterine artery pulsatility index (PI), GRADEpro initially rated the certainty as low, consistent with default ratings for observational studies (S2 Table). However, based on consistent effect direction across studies, low heterogeneity (I² = 26.6%), large pooled sample size (n = 1,656), and low risk of bias, we manually upgraded the certainty to moderate. Although the pooled effect estimate (Hedges’s g = 0.15; 95% CI: 0.03 to 0.26) excluded the null, its small magnitude and use of log-transformed MoM values warranted cautious interpretation (Table 3). In contrast, the certainty of evidence for the resistance index (RI) was rated as very low in both manual and GRADEpro assessments, due to reliance on only two studies (n = 656), wide and non-significant confidence intervals (Hedges’s g = 0.19; 95% CI: –0.06 to 0.43), possible inconsistency, and an inability to assess publication bias.
Results for pulsatility index (PI) meta-analysis
The meta-analysis included six studies examining the PI in 1656 pregnant women with and without a history of cesarean section.
Using a random-effects model (DerSimonian–Laird method), the pooled effect size showed a statistically significant increase in PI for women with a history of cesarean section (Hedges’s g = 0.15, 95% CI [0.03, 0.26], p = 0.01). The analysis revealed low heterogeneity among the studies (I² = 26.60%, p = 0.23), indicating that the variability in effect sizes was primarily due to sampling error rather than true differences between the studies. The test for overall effect was significant (z = 2.45, p = 0.01), suggesting that the history of cesarean section is associated with an increased PI (Fig 2).
Assessment for publication bias using Egger’s regression test indicated no significant small-study effects (p = 0.81), supporting the robustness of the results. The funnel plot did not show significant asymmetry, consistent with Egger’s test results, further confirming the absence of substantial publication bias in the main analysis (Fig 3) and additional sensitivity analysis (S1 Fig). The studies were evenly distributed around the mean effect size, reinforcing the reliability of the meta-analysis findings.
Meta-regression was performed to explore the influence of potential confounders on the observed effect sizes, specifically considering age, BMI, and weeks of gestation. The meta-regression results indicated None of these factors showed a statistically significant impact on the effect size (p > 0.05), indicating that the association between cesarean section history and increased PI was not significantly influenced by these confounders. The residual heterogeneity was significant (Q_res = chi2(5) = 113.96, p < 0.0001), suggesting that other unmeasured factors may contribute to the variability in PI outcomes (S3 Table).
The sensitivity analysis for the PI indicates a statistically significant increase in PI for women with a history of cesarean section (Hedges’s g = 0.18, 95% CI [0.08, 0.29], p = 0.00), with no observed heterogeneity among the studies (I² = 0.00%) (S1 Fig).
Resistance index (RI) meta-analysis
The meta-analysis of the RI included two studies, with a total sample size of 326 participants in the treatment group (history of cesarean section) and 330 participants in the control group (no history of cesarean section). The pooled effect size, calculated using a random-effects model, showed a small increase in RI for women with a history of cesarean section (Hedges’s g = 0.19, 95% CI [−0.06, 0.43], p = 0.13). The heterogeneity among the studies was moderate (I² = 48.08%, p = 0.17), indicating some variability in the results across studies. The test of overall effect (z = 1.50, p = 0.13) suggests that the increase in RI was not statistically significant (Fig 4). For the RI outcome, no definitive interpretation could be made regarding publication bias due to the small number of studies (n = 2).
Discussion
Summary of main results
The results of our meta-analysis indicate a statistically significant increase in the PI in pregnant women with a history of cesarean section compared to those without. This finding is consistent across the studies included in the analysis. However, we needed more data to comprehensively analyse the RI.
General interpretation of the results in the context of other evidence
Our findings align with previous studies that have evaluated the impact of prior cesarean sections on maternal and perinatal outcomes in subsequent pregnancies. For instance, a review by Silver et al. reported that previous cesarean deliveries were associated with increased risks of placental complications, uterine rupture, and adverse neonatal outcomes in subsequent pregnancies [29]. Additionally, Lumbiganon et al. found that women with a history of cesarean section had higher rates of perinatal complications such as low birth weight and neonatal intensive care unit admissions [30]. These findings corroborate our meta-analysis results, which indicate that previous cesarean sections are associated with increased uterine artery resistance, potentially leading to higher rates of adverse outcomes.
The potential mechanism behind the increased PI and its association with adverse outcomes such as preeclampsia, intrauterine growth restriction (IUGR), and preterm labor could be attributed to the impaired trophoblastic invasion of spiral arteries. This results in inadequate remodellingof these arteries, leading to higher resistance and reduced uteroplacental blood flow [31]. The studies included in our meta-analysis reported various adverse perinatal outcomes linked to high PI. As Hashemi et al. found, increased PI correlated with higher incidences of preeclampsia and IUGR, highlighting the clinical significance of monitoring PI in pregnancies with a history of cesarean section [32].
Our study primarily focused on the second trimester, contrasting with studies like those by Filho et al. (2011) and Zarean and Shabaninia (2018), which evaluated uterine artery resistance in the third trimester. Filho et al. found no significant changes in the uterine artery PI between women with elective cesarean sections and those with cesarean sections performed during labor. They concluded that the uterine matrix circulation is robust enough to withstand the scarring from cesarean sections without significant alterations detectable by Doppler velocimetry [33]. On the other hand, Zarean and Shabaninia observed that high uterine artery PI at 30–34 weeks gestation was associated with adverse perinatal outcomes, including small-for-gestational-age fetuses and preeclampsia, although its predictive power alone was limited [34].
Overall, our findings support the need for heightened surveillance of uterine artery resistance in pregnant women with a history of cesarean section, particularly focusing on PI as a critical marker. Future research should include comprehensive data on both PI and RI, and explore the mechanisms further to improve predictive models for adverse perinatal outcomes.
The evaluation of certainty highlights important contrasts between the two outcomes assessed. For PI, while the GRADEpro software initially rated the certainty of evidence as low—due to the observational nature of the included studies—a manual reassessment supported an upgrade to moderate certainty, based on consistent direction of effect, high methodological quality, and low heterogeneity (I² = 26.6%). Although the observed effect size was small and based on log-transformed multiples of the median (MoM), its statistical significance and precision increase confidence in the validity of the association. These findings suggest a likely, though modest, physiological link between prior cesarean section and increased uterine artery resistance. In contrast, the very low certainty for RI, as confirmed by both manual and GRADEpro assessments, reflects the limited number of studies, imprecise and non-significant pooled estimates, and the inability to evaluate publication bias. This disparity reinforces the need for additional high-quality observational research to clarify whether RI can serve as a valid surrogate marker of uteroplacental resistance in this population.
Potential biases and limitations
One of the primary limitations of our study is the lack of a sufficient number of relevant studies. The limited availability of studies reporting the RI prevented us from providing more comprehensive evidence regarding this metric. Additionally, many studies reported the PI in terms of multiples of the median (MoM) instead of providing the actual mean and standard deviation. This necessitated additional calculations and assumptions that could introduce bias and affect the accuracy of our meta-analysis. One of the studies included in the meta-analysis was conducted by our research team. While we were aware of its results during the review process, we adhered strictly to predefined eligibility criteria and objective data extraction procedures to minimize bias and ensure methodological rigor. Another significant limitation is the failure of some studies to disclose the exact number of previous cesarean sections, which is a crucial variable for assessing the impact on uterine artery resistance. During the review process, we encountered difficulties in accessing the full texts of some papers that initially appeared relevant. Despite our efforts to request these articles from journals and authors, we could not obtain the full text. This may have led to the exclusion of potentially relevant data, impacting the comprehensiveness of our review. A further limitation of this review is the geographical concentration of the included studies, with five of the six originating from Asian countries. This may limit the generalizability of the findings to other populations, particularly those in regions with different obstetric practices including rate of cesarean section and Doppler ultrasound cost and availability. For instance, countries such as Turkey, Iran, and China have among the highest cesarean section rates globally, with a substantial proportion being elective rather than medically indicated procedures [35,36]. In parallel, uterine artery Doppler ultrasound is more routinely used in parts of Asia for second-trimester screening [37], particularly for the early identification of preeclampsia and placental insufficiency, whereas its use in many Western countries is typically limited to high-risk pregnancies [38,39]. These regional differences in both clinical practice and patient populations may influence the observed associations and should be considered when interpreting the applicability of our findings in other healthcare settings. To the best of our knowledge, this is the first systematic review and meta-analysis to comprehensively evaluate the impact of prior cesarean delivery on uterine artery Doppler indices, addressing a critical gap in the obstetric literature; additionally, the standardized log-transformation of Doppler values into multiples of the median (MoM) across studies enhanced the comparability and precision of the pooled estimates.
Implications for practice and future research
The results of our meta-analysis suggest an association between a history of cesarean section and increased uterine artery resistance. This finding highlights the importance of careful monitoring of uterine artery resistance in pregnant women with a history of cesarean section to mitigate potential adverse outcomes. Clinicians should consider this factor when managing pregnancies following a cesarean section.
Future research should focus on including larger sample sizes and diverse populations to validate our findings, using standardized Doppler protocols across regions. Studies should also ensure the disclosure of key clinical variables, such as the number and indication of previous cesarean sections, to allow for more precise subgroup analyses. Additionally, facilitating open access to full-text data would improve the completeness of evidence synthesis. Importantly, future studies should investigate the clinical implications of elevated uterine artery resistance in women with prior cesarean deliveries—particularly regarding outcomes such as preeclampsia, fetal growth restriction, and placental insufficiency—to better guide prenatal care.
Conclusion
This meta-analysis suggests that women with a history of cesarean section may exhibit slightly increased uterine artery resistance, as measured by Doppler indices. While the observed association is modest, it may have implications for uteroplacental perfusion and pregnancy outcomes. These findings highlight the potential value of closer monitoring in pregnancies following cesarean delivery, although further research is needed to clarify the clinical significance and guide management strategies.
Supporting information
S1 Table. Detail of search strategies in each database and corresponding queries.
https://doi.org/10.1371/journal.pone.0325352.s001
(DOCX)
S2 Table. The evaluation of certainty using the GradePro software and also manually.
https://doi.org/10.1371/journal.pone.0325352.s002
(DOCX)
S3 Table. Results of meta-regression analysis to identify potential confounding effects.
https://doi.org/10.1371/journal.pone.0325352.s003
(DOCX)
S1 Fig. Sensitivity analysis.
A: Forest plot of the PI meta-analysis following removal of the source of the heterogeneity. B: Funnel plot of the PI meta-analysis following removal of the source of the heterogeneity.
https://doi.org/10.1371/journal.pone.0325352.s004
(PDF)
References
- 1. van der Krogt L, Shennan A. Cervical cesarean damage as a growing clinical problem: The association between in-labour cesarean section and recurrent preterm birth in subsequent pregnancies. PLoS Med. 2024;21(12):e1004497. pmid:39666594
- 2. Jamshed S, Chien S-C, Tanweer A, Asdary R-N, Hardhantyo M, Greenfield D, et al. Correlation Between Previous Caesarean Section and Adverse Maternal Outcomes Accordingly With Robson Classification: Systematic Review and Meta-Analysis. Front Med (Lausanne). 2022;8:740000. pmid:35096855
- 3. Naji O, Wynants L, Smith A, Abdallah Y, Saso S, Stalder C, et al. Does the presence of a Caesarean section scar affect implantation site and early pregnancy outcome in women attending an early pregnancy assessment unit? Hum Reprod. 2013;28(6):1489–96. pmid:23585560
- 4. Ventura Laveriano WR, Redondo CEN. Obstetric outcomes in the second birth of women with a previous caesarean delivery: a retrospective cohort study from Peru. Rev Bras Ginecol Obstet. 2013;35(4):148–52. pmid:23752578
- 5. Hu H-T, Xu J-J, Lin J, Li C, Wu Y-T, Sheng J-Z, et al. Association between first caesarean delivery and adverse outcomes in subsequent pregnancy: a retrospective cohort study. BMC Pregnancy Childbirth. 2018;18(1):273. pmid:29954355
- 6. Dencker A, et al. Neonatal outcomes associated with mode of subsequent birth after a previous caesarean section in a first pregnancy: a Swedish population-based register study between 1999 and 2015. BMJ Paediatr Open. 2022;6(1).
- 7. Torabi S, Sheikh M, Fattahi Masrour F, Shamshirsaz AA, Bateni ZH, Nassr AA, et al. Uterine artery Doppler ultrasound in second pregnancy with previous elective cesarean section. J Matern Fetal Neonatal Med. 2019;32(13):2221–7. pmid:29397792
- 8. Işıkalan MM, Yeniçeri H, Toprak E, Güleroğlu FY, Acar A. Effect of previous cesarean sections on second-trimester uterine artery Doppler. J Obstet Gynaecol Res. 2020;46(9):1766–71. pmid:32875650
- 9. Yapan P, Tachawatcharapunya S, Surasereewong S, Thongkloung P, Pooliam J, Poon LC, et al. Uterine artery Doppler indices throughout gestation in women with and without previous Cesarean deliveries: a prospective longitudinal case-control study. Sci Rep. 2022;12(1):20913. pmid:36463315
- 10. Aygun EG, Karabuk E, Dilek TUK. A Retrospective Cohort Study to Determine Whether the Previous Route of Delivery Affects the Uterine Artery Blood Flow. Cureus. 2023;15(5):e39552. pmid:37378119
- 11. Flo K, Widnes C, Vårtun Å, Acharya G. Blood flow to the scarred gravid uterus at 22-24 weeks of gestation. BJOG. 2014;121(2):210–5. pmid:24112289
- 12. Timor-Tritsch IE, et al. Extreme enhanced myometrial vascularity following cesarean scar pregnancy: a new diagnostic entity. J Matern Fetal Neonatal Med. 2022;35(25):5846–57.
- 13. Timor-Tritsch IE, Haynes MC, Monteagudo A, Khatib N, Kovács S. Ultrasound diagnosis and management of acquired uterine enhanced myometrial vascularity/arteriovenous malformations. Am J Obstet Gynecol. 2016;214(6):731.e1-731.e10. pmid:26873276
- 14. di Pasquo E, Kiener AJO, DallAsta A, Commare A, Angeli L, Frusca T, et al. Evaluation of the uterine scar stiffness in women with previous Cesarean section by ultrasound elastography: a cohort study. Clin Imaging. 2020;64:53–6. pmid:32325262
- 15. Burke SD, Zsengellér ZK, Karumanchi SA, Shainker SA. A mouse model of placenta accreta spectrum. Placenta. 2020;99:8–15. pmid:32716845
- 16. Wenqiang D, Novin A, Liu Y, Afzal J, Suhail Y, Liu S, et al. Scar matrix drives Piezo1 mediated stromal inflammation leading to placenta accreta spectrum. Nat Commun. 2024;15(1):8379. pmid:39333481
- 17. Morgan RL, Whaley P, Thayer KA, Schünemann HJ. Identifying the PECO: A framework for formulating good questions to explore the association of environmental and other exposures with health outcomes. Environ Int. 2018;121(Pt 1):1027–31. pmid:30166065
- 18. Page MJ, McKenzie JE, Bossuyt PM, Boutron I, Hoffmann TC, Mulrow CD, et al. The PRISMA 2020 statement: an updated guideline for reporting systematic reviews. BMJ. 2021;372:n71. pmid:33782057
- 19. Favre R, Ditesheim PJ. Predictive value of Doppler velocimetry in the uterine artery and association of Doppler velocimetry of uterine and umbilical arteries in high risk pregnancies. J de Gynecologie Obstetrique et Biologie de la Reproduction.1991;20(2): 261-8. pmid:2071872
- 20. Gupta A, Kamble A. Triple vessel waveform study in normal and high risk pregnancies and perinatal outcome. J Datta Meghe Institute Medical Sci Univ. 2014;9(1):33–7.
- 21. Iwata M, Mitsuda N, Masuhara K, Fuke S, Shikado K, Bekku S, et al. Prenatal detection of the growth-retarded fetuses with a serious risk of adverse perinatal outcome by uterine artery Doppler flow velocimetry: a prospective study. Nihon Sanka Fujinka Gakkai Zasshi. 1995;47(12):1365–70. pmid:8568356
- 22. Liu JH, et al. Transvaginal color doppler ultrasonography evaluation of transcatheter uterine artery embolization for uterine scar pregnancy. Chinese J Intervent Imaging Ther. 2010;7(3):278–80.
- 23. Stoicescu SM, et al. Clinical considerations and ultrasound examination at premature infants with gestational age less than 32 weeks. Obstetrica si Ginecologie. 2013;61(3):159–65.
- 24. Szabó I, et al. Assessment of uterine arterial blood flow using color and pulsed Doppler ultrasound in pre-eclampsia. Magyar Noorvosok Lapja. 2006;69(4):271–9.
- 25. Stang A. Critical evaluation of the Newcastle-Ottawa scale for the assessment of the quality of nonrandomized studies in meta-analyses. Eur J Epidemiol. 2010;25(9):603–5. pmid:20652370
- 26. Guyatt GH, et al. GRADE: an emerging consensus on rating quality of evidence and strength of recommendations. BMJ. 2008;336(7650):924–6.
- 27.
Manual of diagnostic ultrasound. WHO. 2011.
- 28. Gómez O, Figueras F, Fernández S, Bennasar M, Martínez JM, Puerto B, et al. Reference ranges for uterine artery mean pulsatility index at 11-41 weeks of gestation. Ultrasound Obstet Gynecol. 2008;32(2):128–32. pmid:18457355
- 29. Silver RM. Delivery after previous cesarean: long-term maternal outcomes. Semin Perinatol. 2010;34(4):258–66. pmid:20654776
- 30. Lumbiganon P, Laopaiboon M, Gülmezoglu AM, Souza JP, Taneepanichskul S, Ruyan P, et al. Method of delivery and pregnancy outcomes in Asia: the WHO global survey on maternal and perinatal health 2007-08. Lancet. 2010;375(9713):490–9. pmid:20071021
- 31. Lyall F, Robson SC, Bulmer JN. Spiral artery remodeling and trophoblast invasion in preeclampsia and fetal growth restriction: relationship to clinical outcome. Hypertension. 2013;62(6):1046–54. pmid:24060885
- 32. Hashemi N, Mohazzab A, Moshfeghi M, Rokhgireh S, Derakhshan R, Sanaei Nasab N. Cesarean section and its impact on uterine artery resistance and the risk of pre-eclampsia in subsequent pregnancies. J Reprod Infertil. 2024;25(3):211–8. pmid:39830326
- 33. Filho OOS, et al. Repercussions of previous cesarean uterine scar at uterine arteries doppler velocimetry between the 26th and 32nd gestational weeks. Radiologia Brasileira. 2011;44(3):163–6.
- 34. Zarean E, Shabaninia S. The assessment of association between uterine artery pulsatility index at 30-34 week’s gestation and adverse perinatal outcome. Adv Biomed Res. 2018;7:111.
- 35. Zarshenas M, et al. Incidence and determinants of caesarean section in Shiraz, Iran. Int J Environ Res Public Health. 2020;17(16).
- 36. Santas G, Santas F. Trends of caesarean section rates in Turkey. J Obstet Gynaecol. 2018;38(5):658–62. pmid:29519178
- 37. Shirazi M, et al. Investigating uterine artery doppler indices in normal pregnancies. J Obstetrics Gynecol Cancer Res. 2025;10(4):261–8.
- 38. Gestational hypertension and preeclampsia: ACOG practice bulletin, number 222. Obstet Gynecol. 2020;135(6):e237–60. pmid:32443079
- 39.
Hypertension in pregnancy: diagnosis and management. National Institute for Health and Care Excellence (NICE). 2019.