Obstetric Doppler ultrasonography has become an indispensable modality in contemporary antenatal care, offering a non-invasive window into the uteroplacental and fetoplacental haemodynamic status. By assessing blood flow velocity waveforms in the maternal uterine arteries and fetal umbilical and middle cerebral arteries, Doppler technology enables the early identification of pregnancies at heightened risk for pre-eclampsia, fetal growth restriction (FGR), and perinatal mortality [1–3]. The underlying pathophysiological premise is that defective trophoblastic invasion of the spiral arteries leads to a high-resistance, low-flow placental circulation, which manifests as elevated pulsatility indices and persistent diastolic notching in the uterine arteries, and subsequently as abnormal umbilical and cerebral artery Doppler indices when fetal compensation begins to fail [4,5]. Consequently, abnormal Doppler findings have been strongly correlated with adverse perinatal outcomes, making them valuable surrogate markers for placental insufficiency. The uterine artery Doppler waveform, typically evaluated at the second-trimester anomaly scan or in the early third trimester, is the most studied parameter for predicting pre-eclampsia and FGR. A mean pulsatility index (PI) above the 95th percentile for gestational age, particularly when accompanied by bilateral diastolic notching, identifies women with impaired placentation with a sensitivity of 50–70% for early-onset pre-eclampsia [6,7]. The umbilical artery Doppler reflects downstream placental vascular resistance; an elevated PI or absent/reversed end-diastolic flow signifies increasing placental compromise and is directly associated with fetal hypoxia and acidaemia [8,9]. The middle cerebral artery (MCA) Doppler, in turn, demonstrates a brain-sparing effect a reduction in PI below the 5th percentile indicating fetal haemodynamic redistribution in response to chronic hypoxaemia, which often precedes overt growth restriction [10]. The integrated assessment of these three vascular beds provides a comprehensive picture of feto-placental well-being and is recommended in high-risk pregnancies worldwide [11]. India, with its vast and heterogeneous population, exhibits stark rural–urban disparities in maternal healthcare access, nutritional status, and pregnancy outcomes. Rural women often experience delayed antenatal booking, higher rates of anaemia, chronic energy deficiency, and lower socioeconomic status all factors that can potentiate placental dysfunction [12,13]. National health surveys repeatedly demonstrate that rural populations have poorer maternal health indicators, including higher rates of low birth weight, preterm birth, and maternal mortality, compared to their urban counterparts [14,15]. While Doppler screening is increasingly available even in semi-urban tertiary centres, systematic comparisons of Doppler abnormalities between rural and urban pregnant women are lacking in the Indian literature. Such data would help ascertain whether place of residence independently predicts a higher prevalence of compromised uteroplacental circulation, potentially guiding targeted screening interventions. Against this backdrop, we designed the present cross-sectional study to evaluate and compare the prevalence of abnormal obstetric Doppler findings in rural and urban antenatal populations attending a tertiary care hospital in Pune, India. By employing a comprehensive Doppler examination of the uterine, umbilical, and middle cerebral arteries during the late second and early third trimesters, we aimed to quantify the magnitude of subclinical placental insufficiency in the two groups. The study further sought to generate preliminary evidence that could inform the rational allocation of Doppler ultrasound resources and stimulate larger, multicentre investigations focusing on high-risk rural gravidae. OBJECTIVE The primary objective of this study was to determine and compare the prevalence of abnormal obstetric Doppler findings defined as any abnormal parameter in the uterine, umbilical, or middle cerebral arteries among rural and urban antenatal women attending a tertiary care hospital in Pune, India. By directly contrasting these two groups, the study aimed to identify whether rural residence is associated with a higher burden of compromised uteroplacental and fetoplacental circulation during the window of 28–34 weeks of gestation. The secondary objectives were to estimate the group-specific prevalence of each individual abnormal Doppler marker: elevated uterine artery mean PI or bilateral notching, elevated umbilical artery PI, and reduced middle cerebral artery PI. Additionally, we sought to explore the distribution of abnormal Doppler indices across the entire cohort to understand the relative frequency of different vascular bed involvements. The findings were intended to provide baseline data for the planning of risk-stratified antenatal Doppler screening protocols in mixed rural-urban settings

Study Design and Setting: This was a hospital-based, cross-sectional comparative study conducted in the Department of Obstetrics and Gynaecology at Sai Shree Tertiary Care Hospital, a large referral centre in Pune, Maharashtra, India. The hospital serves a diverse population, with approximately half of the antenatal attendees coming from the surrounding rural blocks and the remainder from the urban agglomeration of Pune. The study was carried out over a period of nine months, from 1st July 2025 to 25th March 2026, after obtaining approval from the Institutional Ethics Committee (IEC/2025/OBG/14). All participants provided written informed consent. Sample Size and Sampling: A total of 36 pregnant women were enrolled using a convenience sampling technique, with 18 women in the rural group and 18 in the urban group. The sample size was determined based on the feasibility of recruiting an adequate number of participants within the study period from each residential stratum, as no prior local data on Doppler prevalence differences were available for formal power calculation. This pilot-sized sample was considered sufficient to generate preliminary prevalence estimates and inform future larger-scale studies. Inclusion Criteria: Women with a singleton pregnancy at a gestational age of 28–34 completed weeks (confirmed by first-trimester ultrasound or reliable last menstrual period), aged between 18 and 40 years, and classified as either rural or urban residents according to the Census of India definition (rural: residing in a village with a population <5,000 and not falling under an urban agglomeration; urban: residing within municipal corporation limits). Only women who were willing to comply with the Doppler examination and follow-up schedule were included. Exclusion Criteria: Pregnancies complicated by multiple gestation, known major fetal congenital anomalies, pre-existing chronic hypertension, pre-gestational diabetes mellitus, renal or autoimmune disorders, or a history of pre-eclampsia or FGR in a previous pregnancy were excluded. Women with preterm prelabour rupture of membranes, active preterm labour, or those who had already received corticosteroids for fetal lung maturity were also excluded, as these conditions could independently alter Doppler indices. Data Collection Procedure: After enrolment, a structured questionnaire was administered to collect sociodemographic data including age, parity, educational status, occupation, and detailed residential address to confirm rural/urban status. Anthropometric measurements (height, weight) were taken, and body mass index (BMI) was calculated. Obstetric history and baseline clinical parameters such as blood pressure were recorded. All participants then underwent a comprehensive Doppler ultrasound examination using a Voluson E10 machine (GE Healthcare, USA) equipped with a 2–5 MHz curvilinear transducer. A single experienced maternal-fetal medicine sonographer, blinded to the residence category, performed all scans to minimise inter-observer variability. Doppler measurements were acquired during fetal quiescence and maternal semi-recumbent position, with an angle of insonation kept below 30°. The uterine arteries were interrogated bilaterally at the level of the internal os; the mean PI was calculated, and the presence of bilateral early diastolic notching was noted. Umbilical artery Doppler waveforms were obtained from a free-floating loop of cord, and the PI was recorded. The middle cerebral artery was insonated at its origin from the circle of Willis, and the PI was measured. All indices were averaged over three consecutive uniform waveforms. Abnormal Doppler was defined as follows: uterine artery mean PI >95th percentile for gestational age and/or bilateral diastolic notching [1,6]; umbilical artery PI >95th percentile [8]; and MCA PI <5th percentile [10]. Reference ranges derived from large population studies were used [7,16]. Statistical Data Analysis: Data were entered into Microsoft Excel and analysed using SPSS version 26.0 (IBM Corp., Armonk, NY). Continuous variables were expressed as mean ± standard deviation and compared between rural and urban groups using the independent samples t-test if normally distributed; otherwise, the Mann-Whitney U test was employed. Categorical variables were summarised as frequencies and percentages. The primary outcome prevalence of any abnormal Doppler finding and the secondary outcomes individual parameter abnormalities were compared using the Fisher’s exact test owing to the small sample size and expected cell frequencies. A two-sided p-value <0.05 was considered statistically significant. Descriptive bar and pie charts were generated to visualise the comparative prevalence and the distribution of abnormal Doppler types.

A total of 36 pregnant women (18 rural, 18 urban) completed the study protocol. The baseline demographic and clinical characteristics were comparable between the two groups (Table 1). The mean maternal age was 26.4 ± 4.2 years in the rural group and 27.1 ± 3.8 years in the urban group (p=0.602). The mean gestational age at the time of Doppler examination was 31.2 ± 1.8 weeks and 31.5 ± 1.7 weeks, respectively (p=0.611). Mean BMI was slightly lower in the rural women (23.4 ± 2.9 kg/m²) compared to urban women (24.6 ± 3.1 kg/m²), though the difference was not statistically significant (p=0.247). The proportion of primigravida women was 38.9% in the rural and 44.4% in the urban group (p>0.99). Thus, the groups were well matched, minimizing potential confounding. Table 1: Baseline Characteristics of Study Participants Characteristic Rural (n=18) Urban (n=18) p-value Age (years), mean ± SD 26.4 ± 4.2 27.1 ± 3.8 0.602 Gestational age at scan (weeks), mean ± SD 31.2 ± 1.8 31.5 ± 1.7 0.611 BMI (kg/m²), mean ± SD 23.4 ± 2.9 24.6 ± 3.1 0.247 Primigravida, n (%) 7 (38.9) 8 (44.4) >0.99* Systolic BP (mmHg), mean ± SD 112.4 ± 8.3 114.1 ± 7.9 0.541 Diastolic BP (mmHg), mean ± SD 72.1 ± 6.5 73.8 ± 6.1 0.424 *Fisher’s exact test; BP: blood pressure; SD: standard deviation. The overall prevalence of any abnormal Doppler finding in the study cohort was 36.1% (13 out of 36 women). When stratified by residence, abnormal Doppler parameters were detected in 8 of the 18 rural women (44.4%), whereas only 5 of the 18 urban women (27.8%) had at least one abnormal index. Despite this apparent 16.6% absolute difference, the discrepancy did not reach statistical significance (p=0.305, Fisher’s exact test) (Table 5, Figure 1). Table 2: Comparison of Abnormal Uterine Artery Doppler Findings Uterine Artery Doppler Rural (n=18) Urban (n=18) p-value* Abnormal, n (%) 6 (33.3) 3 (16.7) 0.443 Mean PI >95th centile alone 4 (22.2) 2 (11.1) – Bilateral notching present 4 (22.2) 1 (5.6) – *Fisher’s exact test for overall abnormal. Table 3: Comparison of Abnormal Umbilical Artery Doppler Findings Umbilical Artery Doppler Rural (n=18) Urban (n=18) p-value* Abnormal (PI >95th centile), n (%) 4 (22.2) 2 (11.1) 0.658 Table 4: Comparison of Abnormal Middle Cerebral Artery Doppler Findings MCA Doppler Rural (n=18) Urban (n=18) p-value* Abnormal (PI <5th centile), n (%) 3 (16.7) 1 (5.6) 0.603 *Fisher’s exact test. Table 5: Overall Prevalence of Any Abnormal Doppler Finding Any Abnormal Doppler Rural (n=18) Urban (n=18) Total (N=36) p-value* Present, n (%) 8 (44.4) 5 (27.8) 13 (36.1) 0.305 Absent, n (%) 10 (55.6) 13 (72.2) 23 (63.9) *Fisher’s exact test. Among the specific vascular beds, uterine artery abnormalities were the most prevalent, occurring in 33.3% of rural and 16.7% of urban participants (p=0.443). The umbilical artery PI was elevated in 22.2% and 11.1% of rural and urban women, respectively (p=0.658). Brain-sparing (low MCA PI) was noted in 16.7% of the rural group compared to 5.6% in the urban group (p=0.603). No instances of absent or reversed end-diastolic flow in the umbilical artery were observed. The bar chart (Figure 1) visually contrasts the prevalence of any abnormal Doppler between the two groups, highlighting the non-significant but consistently higher rates in the rural population. When the 13 women with any abnormality were examined for the type of Doppler derangement, a total of 19 abnormal parameter instances were recorded, as some women had more than one altered index. The pie chart (Figure 2) illustrates the distribution of these 19 abnormalities: uterine artery Doppler accounted for 9 instances (47.4%), umbilical artery for 6 (31.6%), and MCA for 4 (21.1%). This indicates that uteroplacental dysfunction was the predominant manifestation of compromised Doppler findings in our sample, often preceding downstream fetal circulatory changes.

This cross-sectional pilot study demonstrated that the point prevalence of abnormal obstetric Doppler indices was notably high in our antenatal population, with over one-third of participants exhibiting at least one deranged parameter. This figure exceeds the 5–15% prevalence of isolated uterine artery notching or elevated PI generally reported in low-risk or unselected populations [1,7,17]. The elevated prevalence in our cohort likely reflects the tertiary care setting, where a significant proportion of referred or self-referred women carry risk factors, even if they do not meet the traditional high-risk criteria. Moreover, the inclusion of umbilical and middle cerebral artery Doppler in addition to the uterine artery broadened the detection of haemodynamic alterations, capturing compensated fetal states that might be missed by uterine artery screening alone. Crucially, the rural group consistently demonstrated a higher prevalence of abnormal Doppler findings across all three vascular beds, although the differences did not reach statistical significance. The 44.4% prevalence of any abnormality in rural women compared to 27.8% in urban women represents a clinically meaningful 16.6 percentage point excess. This trend aligns with the well-documented socioeconomic and nutritional disparities that characterise rural Indian populations. Rural women are more likely to suffer from chronic energy deficiency, iron-deficiency anaemia, and micronutrient inadequacies, each of which has been implicated in impaired placental development and increased uteroplacental resistance [13,18]. Anaemia, in particular, is associated with a hyperdynamic circulation that may mask or modify Doppler indices, yet it frequently coexists with placental hypoxia, potentially leading to elevated umbilical artery PI [19]. Our urban participants, by contrast, had marginally higher BMI and are presumed to have better access to balanced nutrition and earlier antenatal care, which may partially protect against placental vascular compromise. The observed patterns of Doppler abnormality offer pathophysiological insight. Uterine artery abnormalities the most common finding reflect the primary defect of inadequate trophoblastic remodelling of spiral arteries, an event that occurs in the first half of pregnancy and is influenced by maternal nutritional and immunological status [4,5]. The higher rate of bilateral notching in the rural group (22.2% vs. 5.6%) suggests more severe impairment of the uteroplacental unit. Umbilical artery PI elevation, indicative of increased downstream vascular resistance within the placental villous tree, was twice as frequent in rural participants. Similarly, the brain-sparing phenomenon (low MCA PI), a sign of chronic fetal hypoxia and redistribution of cardiac output, was three-fold more common in the rural cohort. Although the sample size precluded statistical confirmation, the consistency of these findings across complementary Doppler indices strengthens the suggestion that rural residence may independently predispose to a higher burden of placental insufficiency. Comparisons with the existing literature are limited by the paucity of studies that directly contrast rural and urban Doppler profiles. A Nigerian study by Oluwasola et al. found that low socioeconomic status was significantly associated with abnormal uterine artery Doppler indices, a proxy for rural disadvantage [20]. Indian investigations focusing on high-risk pregnancies have reported uterine artery abnormality rates of 30–40% in women with adverse outcomes [21,22], values that approximate the prevalence in our rural subset. Yet, the application of Doppler in unselected populations to predict rural-urban disparities remains unexplored. Our data, while preliminary, fill a critical gap by providing the first head-to-head comparison in an Indian tertiary hospital. The absence of statistically significant differences must be interpreted with caution. The small sample size (n=36) yields limited statistical power; a post-hoc power calculation indicated that a study would need approximately 130 participants per group to detect a 16% difference with 80% power at α=0.05. Thus, the lack of significance likely reflects a type II error rather than a true absence of disparity. The clinical importance of the trend, however, should not be dismissed, given the severe consequences of undetected placental dysfunction pre-eclampsia, FGR, iatrogenic preterm birth, and stillbirth. In resource-constrained rural areas where access to serial fetal surveillance is limited, incorporating a one-time comprehensive Doppler evaluation at 28–34 weeks could identify a substantial number of at-risk pregnancies that would otherwise remain unrecognized. Such a strategy aligns with the WHO’s 2016 recommendations to integrate evidence-based screening tools into antenatal care packages, especially for vulnerable populations [11]. Another notable finding was the distribution of abnormalities: uterine artery Doppler accounted for almost half of all detected derangements. This reinforces the central role of uteroplacental insufficiency as the initiator of the cascade leading to fetal compromise. The presence of isolated MCA brain-sparing in a few cases without umbilical artery abnormality suggests early fetal adaptation and emphasises the value of multi-vessel Doppler to capture compensated hypoxic states that might otherwise be missed. As previous studies have shown, the sequence of Doppler deterioration from uterine to umbilical to MCA heralds progressive worsening, and early detection provides a window for interventions such as corticosteroid administration, maternal rest, nutritional supplementation, and timed delivery [3,10]. Limitations of the Study This study has several limitations that must be acknowledged. First, the sample size of 36 is modest and was dictated by the available recruitment window in a single tertiary care centre; consequently, the study was underpowered to detect statistically significant differences between groups, and the results must be viewed as exploratory. Second, the cross-sectional design precluded follow-up of pregnancy outcomes; therefore, the prognostic significance of the observed Doppler abnormalities in terms of pre-eclampsia, birth weight, or perinatal morbidity could not be assessed, weakening the clinical applicability of the prevalence estimates. Third, the use of convenience sampling may have introduced selection bias, as women accessing a tertiary hospital even those from rural areas are likely to differ from the general rural population in health-seeking behaviour and risk profile. The study also lacked information on important confounders such as detailed dietary intake, serum haemoglobin levels, and biomarkers of placental function, which could have refined the analysis. The Doppler definitions relied on reference ranges derived from largely Caucasian or mixed populations, although validated locally in some Indian studies; population-specific nomograms would enhance accuracy. Finally, a single sonographer performed all scans, which eliminates inter-observer variation but limits the external validity of the findings; future multicentre studies with blinded, multiple operators are required. Acknowledgment The authors gratefully acknowledge the antenatal women who participated in this study for their cooperation and trust. We thank the nursing staff and sonography team of the Department of Obstetrics and Gynaecology, Sai Shree Tertiary Care Hospital, for their invaluable assistance in participant recruitment and data collection. We also extend our sincere gratitude to the hospital administration for providing the infrastructure and support necessary to complete this research.

This cross-sectional comparative study, despite its limited sample size, suggests a clinically relevant trend towards a higher prevalence of abnormal obstetric Doppler findings in rural pregnant women compared to their urban counterparts attending a tertiary care centre in Pune, India. With 44.4% of rural participants demonstrating at least one deranged Doppler index most commonly elevated uterine artery resistance the findings underscore a potentially greater burden of subclinical placental insufficiency in populations that already face disparate maternal and perinatal outcomes. The lack of statistical significance is almost certainly attributable to low statistical power, and the consistency of the trend across uterine, umbilical, and middle cerebral arteries warrants serious consideration. The implications of these results extend beyond mere academic interest. If larger, adequately powered studies confirm that rural residence independently predicts abnormal uteroplacental haemodynamics, Doppler ultrasound could become a cost-effective screening adjunct in India’s rural antenatal clinics. Early identification of women at risk for pre-eclampsia and fetal growth restriction would enable targeted interventions nutritional optimisation, aspirin prophylaxis, closer fetal surveillance, and timely referral that could substantially reduce adverse outcomes. The integration of a single comprehensive Doppler evaluation at 28–34 weeks into the existing antenatal care framework, particularly in underserved rural areas, holds promise as a pragmatic public health strategy. Nevertheless, robust multicentre research incorporating longitudinal follow-up, placental biomarkers, and locally derived Doppler reference ranges is imperative before such policies can be advocated. Our study provides the essential preliminary data to justify and design those future investigations, ultimately aiming to bridge the rural-urban gap in maternal-fetal health.

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