Introduction

During pregnancy, the maternal cardiovascular system undergoes extensive physiological adaptations to ensure adequate uteroplacental perfusion and support fetal development. These hemodynamic modifications include increased blood volume, cardiac output (CO), and heart rate (HR), accompanied by a reduction in systemic vascular resistance (SVR) and an elevation in minute ventilation1,2. While these adaptations are essential for optimizing fetal oxygenation and nutrient transfer, they may also exacerbate preexisting cardiovascular conditions or reveal previously undiagnosed cardiac pathologies. Previous studies indicate that cardiovascular disease is detected in approximately 1% to 4% of pregnancies, with asymptomatic cardiac dysfunction identified in 5.2% of pregnant women3,4. Given the substantial cardiovascular demands imposed by pregnancy, deviations from these physiological responses can contribute to significant maternal morbidity and mortality5,6,7. Cardiovascular disease remains the leading cause of indirect maternal mortality, accounting for over 33% of pregnancy-related deaths. It complicates up to 4% of pregnancies, with this prevalence rising to 16% in individuals with preexisting cardiac conditions. Notably, more than 50% of maternal deaths occur postpartum, with up to 68% of cardiovascular-related fatalities considered preventable8. Therefore, a thorough understanding of maternal cardiovascular adaptations during pregnancy is essential for optimizing clinical management, particularly in high-risk populations.

Despite the critical importance of assessing maternal cardiac function, comprehensive gestation-specific reference ranges for key echocardiographic and Doppler-derived cardiovascular parameters remain inadequately established in Chinese pregnant women. Population-specific physiological variations, gestational age-related changes, and ethnic differences contribute to inconsistencies in reported values9,10. Existing literature highlights the significant interplay between maternal cardiovascular function and pregnancy outcomes. Tay et al. demonstrated that maternal cardiovascular function is strongly associated with uterine and feto-placental Doppler indices in both normal and complicated pregnancies, with an elevated uterine artery pulsatility index (PI) in fetal growth restriction (FGR), suggesting compromised maternal hemodynamics11.

Similarly, Melchiorre et al. investigated cardiac function in 559 nulliparous pregnancies, revealing distinct hemodynamic changes. Early pregnancy was characterized by enhanced myocardial function, followed by a progressive decline in cardiac performance, culminating in diastolic dysfunction and impaired myocardial relaxation at term. A reduction in stroke volume index (SVI) was observed, suggesting that some pregnancies exhibit cardiovascular maladaptation12. Additionally, Lihme et al. reported that low CO is associated with an increased risk of preeclampsia, particularly before 37 weeks, in both FGR and non-FGR pregnancies. Their findings suggest that serial third-trimester cardiovascular assessments may aid in identifying at-risk individuals for early monitoring and intervention13.

Further investigations by Sonaglioni et al. demonstrated that hypertensive disorders of pregnancy (HDP) are associated with subclinical myocardial function impairment, highlighting the impact of pregnancy-induced hypertension on left atrial mechanics14. In a separate study, the group of Sonaglioni et al. identified a correlation between gestational diabetes mellitus (GDM) and subclinical myocardial dysfunction, suggesting that metabolic complications during pregnancy may contribute to cardiovascular abnormalities15.

Given the substantial hemodynamic changes that occur during pregnancy, conventional echocardiographic norms derived from non-pregnant populations may not accurately reflect physiological adaptations, complicating the differentiation between normal and pathological states. Establishing pregnancy-specific echocardiographic reference values is imperative for improving early detection of cardiovascular complications, refining risk stratification, and optimizing maternal cardiovascular care.

Although cardiovascular adaptation during pregnancy has been extensively studied, well-defined trimester-specific echocardiographic reference ranges for pregnant women remain scarce, particularly for Asian populations. The majority of existing normative datasets are derived from Western or ethnically heterogeneous cohorts, despite accumulating evidence that cardiac morphology, ventricular remodeling patterns, diastolic function indices, and hemodynamic responses differ substantially across ethnic groups16,17,18. Consequently, the direct application of these reference standards may limit the accurate interpretation of maternal cardiac function in Chinese women and hinder the distinction between physiological gestational remodeling and early pathological alterations.

In response to this unmet need, the present study was designed to systematically establish gestational age–specific reference values for maternal cardiac structure, systolic and diastolic function, and hemodynamics in a large cohort of healthy Chinese pregnant women. By comprehensively quantifying echocardiographic and Doppler-derived parameters across all trimesters using standardized imaging protocols, this investigation aims to delineate normative patterns of maternal cardiovascular adaptation throughout pregnancy. The establishment of these population-specific reference ranges provides an essential framework for improving the accuracy of maternal cardiovascular assessment, facilitating early identification of subclinical cardiac dysfunction, and ultimately contributing to the prevention of adverse maternal and fetal outcomes.

Materials and methods

Ethical approval and informed consent

This study was approved by the Medical Research Ethics Review Committee of Yichun Maternal & Child Health Hospital, Jiangxi, China (Approval Number: 2025004-LW004). All research procedures involving human participants were conducted in accordance with institutional ethical standards and the principles outlined in the latest revision of the Declaration of Helsinki. To ensure patient confidentiality, all data were anonymized prior to analysis. Written informed consent was obtained from all participants prior to enrollment.

Study setting and participants

This prospective observational study included 412 pregnant women with singleton gestations who underwent fetal level II prenatal ultrasound examinations at Yichun Maternal & Child Health Hospital between May 2024 and April 2025. Gestational age (GA) was determined based on the estimated date of confinement using crown-rump length (CRL) measurements obtained during first-trimester sonographic assessments (8–14 weeks of gestation)19. Inclusion criteria required singleton pregnancies with no known maternal comorbidities or fetal abnormalities. Exclusion criteria included any history of chromosomal abnormalities, major fetal structural anomalies, or maternal medical complications.

Ultrasound evaluations were performed using the Voluson E10 ultrasound system (General Electric Medical Systems, Milwaukee, WI, USA) equipped with a C2-9-D multifrequency transabdominal transducer (XDclear Wide Band Convex Probe). All fetal anatomical surveys and biometric measurements were conducted in accordance with the practice guidelines of the International Society of Ultrasound in Obstetrics and Gynecology (ISUOG) and the American Institute of Ultrasound in Medicine (AIUM). To ensure safety, all ultrasound procedures were performed in adherence to the “as low as reasonably achievable” (ALARA) principle20. All scans and measurements were performed by a single board-certified obstetric sonographer with over 10 years of clinical experience. Intraobserver reliability was assessed using reliability statistics, based on repeated measurements conducted by the same examiner.

Maternal echocardiographic assessment

All participants underwent comprehensive transthoracic echocardiographic examination using a Philips Affiniti 70 ultrasound system (Koninklijke Philips N.V., The Netherlands) equipped with an S5-1 broadband sector transducer. Examinations were performed with participants in the left lateral decubitus position.

Echocardiographic image acquisition and quantitative measurements were conducted according to the recommendations of the American Society of Echocardiography (ASE) for comprehensive adult transthoracic echocardiography21. Standard parasternal, apical, and great-vessel views were obtained to assess cardiac chamber dimensions, ventricular systolic and diastolic function, valvular annular dimensions, and systemic and pulmonary outflow hemodynamics.

Two-dimensional echocardiography, M-mode imaging, pulsed-wave Doppler, and tissue Doppler imaging were used to evaluate left ventricular structure and function, transmitral inflow, myocardial relaxation indices, and great-artery flow parameters. All Doppler assessments were performed while the pregnant women were breathing calmly. For each measurement, three consecutive stable waveforms were selected, and the mean values were calculated. Using the built-in software of the ultrasound system, most Doppler indices were automatically computed once the Doppler waveform was accurately traced.

All echocardiographic examinations and quantitative measurements were performed by a single board-certified echocardiography specialist with over 10 years of clinical experience. To assess intraobserver reliability of the echocardiographic measurements obtained during maternal examinations, two repeated measurements were performed by the same experienced examiner. A total of 20 aortic diameter measurements were randomly selected for analysis. Internal consistency between the paired measurements was evaluated using Cronbach’s alpha. Cochran’s Q test was additionally applied to determine whether significant differences existed between the repeated measurements across participants. Descriptive statistics, including the range, mean, and standard deviation of the measurement differences, were calculated to further characterize measurement variability.

Statistical analysis

All data were analyzed using SPSS version 27.0 (IBM Corp., Armonk, NY, USA). Continuous variables were expressed as mean ± standard deviation (SD). Differences across trimesters were assessed using one-way analysis of variance (ANOVA) with post-hoc Bonferroni correction when appropriate. Non-parametric tests were applied for variables not following a normal distribution. A two-tailed p value < 0.05 was considered statistically significant.

Conference presentation

This study of the primary results will be presented by e-poster at the 17th Congress of the Asian Federation of Societies for Ultrasound in Medicine and Biology abstract (12–14 March 2026, Da Nang, Vietnam)

Result

Study population

A total of 412 healthy Chinese pregnant women were enrolled in this study, including 19 participants in the first trimester, 186 in the second trimester, and 209 in the third trimester. Among all valid singleton pregnancies, 9 cases (2.2%) resulted from in vitro fertilization (IVF), while 403 cases (97.8%) were conceived spontaneously. The median maternal age in the three trimester groups was 29.0 years (range, 20–40 years) in the first trimester, 30.0 years (range, 18–43 years) in the second trimester, and 29.0 years (range, 18–45 years) in the third trimester. Statistical analysis demonstrated no significant difference in maternal age among the three groups (p = 0.395). The median gestational age at the time of ultrasound examination was 11 + 5 weeks (range, 6 + 0–12 + 7 weeks) for the first trimester, 19 + 1 weeks (range, 13 + 1–27 + 6 weeks) for the second trimester, and 33 + 1 weeks (range, 28 + 0–40 + 2 weeks) for the third trimester.

Assessment of measurement repeatability

To address the concern regarding intraobserver reliability, we performed a detailed reliability analysis using 20 randomly selected aortic diameter measurements obtained during maternal echocardiographic examinations. Two repeated measurements were taken by the same examiner to evaluate intraobserver consistency. The results demonstrated excellent internal consistency, with a Cronbach′s alpha of 1.000. Additionally, Cochran′s Q test was conducted to assess whether any significant differences existed between the repeated measurements across participants. The analysis showed no statistically significant difference (Cochran′s Q = 0.250, p = 0.617), confirming the stability and reproducibility of the measurements. The measurement differences ranged from − 0.02 to 0.01, with a mean of 0.0010 and a standard deviation of 0.00912.

Left ventricular morphologic remodeling

Quantitative echocardiographic analysis demonstrated progressive structural remodeling of the left ventricle (LV) and atria across gestation, consistent with physiologic adaptation to increased circulatory volume during pregnancy. As shown in Table 1, both the left ventricular internal diameter in diastole (LVIDd) and in systole (LVIDs) increased significantly from 4.36 ± 0.35 cm to 4.66 ± 0.36 cm (p < 0.001) and from 2.83 ± 0.31 cm to 3.07 ± 0.31 cm (p < 0.001), respectively. Correspondingly, the LV end-diastolic volume (EDV) and end-systolic volume (ESV) rose markedly (EDV: 86.96 ± 19.1 mL → 100.44 ± 20.6 mL, p < 0.001; ESV: 32.13 ± 8.9 mL → 38.70 ± 9.3 mL, p < 0.001), confirming progressive chamber dilation with advancing gestation.

Table 1 Distribution of maternal cardiac biometries across trimester(N = 412).
Full size table

In contrast, the interventricular septal thickness in diastole (IVSd) and the posterior wall thickness in diastole (LVPWd) remained relatively stable throughout pregnancy (both p > 0.05), while systolic wall thicknesses (IVSs and LVPWs) exhibited only minor, non-significant increases. The IVS/LVPW ratio and IVS percentage (IVS%) showed no significant change.

Atrial and ventricular dimensional parameters exhibited parallel trends of physiologic enlargement. The left atrial vertical (LAVD) and transverse (LATD) diameters increased significantly (LAVD: 3.58 ± 0.33 cm → 3.93 ± 0.37 cm, p < 0.001), and right atrial dimensions (RAVD, RATD) also demonstrated proportional increases (p < 0.05). Similarly, ventricular longitudinal and transverse dimensions (LVLD, LVTD, RVLD, RVTD) expanded modestly, consistent with overall cardiac chamber dilation.

In addition, the atrioventricular and semilunar valve annular diameters increased significantly across trimesters. The mitral valve (MV), tricuspid valve (TV), aortic valve (AO), and pulmonary valve (PA) annuli each exhibited small but statistically significant enlargements (p < 0.05 for all). (Table 1)

Left ventricular systolic function and hemodynamics

Echocardiographic assessment demonstrated progressive enhancement in left ventricular (LV) systolic performance and systemic hemodynamics across gestation, reflecting the physiologic cardiovascular adaptation to pregnancy. As shown in Table 2, stroke volume (SV) increased significantly from 55.26 ± 15.54 mL in the first trimester to 62.39 ± 12.65 mL in the third trimester (p = 0.001), while cardiac output (CO) rose from 4.77 ± 1.60 L/min to 5.91 ± 1.47 L/min (p < 0.001), indicating a marked elevation in circulatory efficiency to accommodate maternal and fetal demands.

Table 2 Distribution of maternal cardiac functions across trimester(N = 412).
Full size table

Although a mild reduction was observed in left ventricular ejection fraction (LV EF: 63.14 ± 5.87% → 61.60 ± 7.40%, p = 0.023) and fractional shortening (LV FS: 34.18 ± 4.48% → 33.51 ± 4.78%, p = 0.076), both parameters remained within normal physiological limits.

Left ventricular diastolic function and hemodynamics

Diastolic parameters demonstrated distinct gestational alterations consistent with physiologic hemodynamic adaptation during pregnancy. As shown in Table 2, the mitral inflow E-wave velocity increased modestly across trimesters, while the A-wave velocity exhibited a more pronounced rise, resulting in a slight but statistically significant reduction in the E/A ratio (p < 0.05). Tissue Doppler imaging revealed a progressive decrease in early diastolic myocardial velocities (e′) at both the septal and lateral annuli. The septal e′ velocity declined from 11.49 ± 1.96 cm/s in the first trimester to 10.75 ± 1.82 cm/s in the third trimester (p < 0.001), and the lateral e′ velocity decreased from 15.68 ± 2.62 cm/s to 13.96 ± 2.34 cm/s (p < 0.001). In contrast, late diastolic velocities (a′) increased significantly throughout gestation (septal a′: 6.76 ± 1.04 cm/s → 7.17 ± 1.09 cm/s, p = 0.002; lateral a′: 6.29 ± 1.12 cm/s → 6.68 ± 1.14 cm/s, p = 0.003). Consequently, the e′/a′ ratios showed a significant downward trend at both the septal and lateral annuli (septal e′/a′: 1.72 ± 0.38 → 1.53 ± 0.32, p < 0.001; lateral e′/a′: 2.54 ± 0.59 → 2.14 ± 0.51, p < 0.001). Additionally, the lateral wall E/e′ ratio increased modestly from 6.09 ± 1.01 to 6.73 ± 1.05 (p = 0.002), reaching statistical significance. Despite these variations, all indices remained within the normal physiologic range.

Ascending aorta and main pulmonary artery hemodynamics

Hemodynamic assessment of the great arteries demonstrated mild but consistent changes in both ascending aortic (AO) and main pulmonary artery (PA) flow indices across gestation, suggesting subtle physiologic vascular adaptation rather than pathological hemodynamic alteration. As shown in Table 2, the ascending aorta peak systolic velocity (AO pSV) increased slightly from 131.11 ± 22.84 cm/s in the first trimester to 137.00 ± 22.34 cm/s in the third trimester (p = 0.372), and the mean velocity (AO mV) rose from 83.63 ± 14.15 cm/s to 90.48 ± 16.09 cm/s (p = 0.071). Correspondingly, the aortic peak pressure gradient (AO pPG) and mean pressure gradient (AO mPG) exhibited minimal, non-significant increases (AO pPG: 7.11 ± 2.62 mmHg → 7.70 ± 2.61 mmHg, p = 0.393; AO mPG: 3.42 ± 1.39 mmHg → 3.99 ± 1.46 mmHg, p = 0.120).

A similar pattern was observed in the main pulmonary artery (PA). The PA peak systolic velocity (PA pSV) increased from 98.22 ± 12.61 cm/s in the first trimester to 105.20 ± 17.27 cm/s in the third trimester (p = 0.118), and the mean velocity (PA mV) rose from 63.93 ± 9.05 cm/s to 69.84 ± 11.83 cm/s (p = 0.064). Notably, the pulmonary artery peak pressure gradient (PA pPG) showed a statistically significant increase from 3.84 ± 1.12 mmHg to 4.54 ± 1.56 mmHg (p = 0.044), while the mean pressure gradient (PA mPG) demonstrated a non-significant upward trend (p = 0.095).

Discussion

In this study, we systematically investigated gestational alterations in cardiac morphology, systolic and diastolic function, and vascular hemodynamics among healthy Chinese pregnant women using comprehensive quantitative echocardiographic and Doppler analyses. Pregnancy is known to elicit profound and dynamic cardiovascular adaptations to accommodate the increasing metabolic demands of both the mother and the developing fetus. These adaptations involve structural remodeling, functional modulation, and hemodynamic reorganization of the maternal heart and great vessels. Our findings demonstrate a coordinated pattern of physiologic eccentric ventricular remodeling, augmented cardiac output, and adaptive diastolic and vascular responses across trimesters, all consistent with normal gestational physiology. Furthermore, the establishment of trimester-specific reference data provides a valuable framework for improving the diagnostic precision of echocardiographic evaluation in Chinese pregnancies. These normative insights will facilitate the differentiation between physiologic cardiovascular adaptation and early pathologic remodeling, thereby enhancing maternal cardiac assessment and clinical decision-making during pregnancy.

Left ventricular morphologic remodeling

The progressive enlargement of left ventricular (LV) and atrial dimensions observed in this study reflects a physiologic adaptation to the hemodynamic load of pregnancy. Significant increases in LV end-diastolic and end-systolic diameters and volumes, along with stable wall thickness and preserved interventricular septum-to-posterior wall ratio, indicate an eccentric remodeling pattern rather than concentric hypertrophy22. This remodeling allows the maternal heart to accommodate sustained volume expansion and decreased systemic vascular resistance, maintaining optimal cardiac output and uteroplacental perfusion without evidence of pathologic hypertrophy or dysfunction.

These findings are consistent with echocardiographic and speckle-tracking studies reporting reversible chamber dilation and increased LV compliance as hallmarks of normal gestation12,23,24,25. Melchiorre et al. and de Haas et al. demonstrated that LV cavity enlargement parallels volume overload, while myocardial mass increases only modestly, preserving physiologic wall stress12,26. The lack of septal or posterior wall thickening in our cohort contrasts with the concentric hypertrophy typical of hypertensive disorders of pregnancy or maladaptive remodeling in preeclampsia13,14,27.

Concurrent expansion of atrial diameters and enlargement of atrioventricular and semilunar annuli further support enhanced global cardiac compliance, facilitating greater preload accommodation and stroke volume augmentation as gestational blood volume rises by up to 50%2,24,25. Naqvi et al. reported similar atrioventricular enlargement in 3D echocardiography, attributed to hormonal and hemodynamic influences28. Mahendru et al. and Soma-Pillay et al. emphasized the reversibility of these changes postpartum, confirming their physiologic nature24,25.

Overall, the structural remodeling pattern in Chinese women mirrors that in other populations, characterized by chamber dilation with preserved wall thickness and systolic function. This physiologic eccentric remodeling highlights the need for ethnicity-specific echocardiographic reference values to distinguish normal gestational changes from pathologic cardiac enlargement and improve maternal cardiovascular risk assessment9,10,29,30.

Left ventricular systolic function and hemodynamics

The observed increases in stroke volume (SV) and cardiac output (CO) across trimesters signify a hallmark physiologic enhancement of systolic performance in response to the progressive hemodynamic demands of pregnancy. Despite mild, statistically insignificant declines in left ventricular ejection fraction (EF) and fractional shortening (FS), both remained well within normal limits, indicating preserved global systolic function despite increased preload and afterload. This pattern reflects the well-established physiologic response whereby the heart augments forward flow primarily by increasing SV, facilitated by eccentric remodeling and reduced systemic vascular resistance2,12,24,25,28.

The modest decrease in EF observed in late pregnancy is consistent with findings from Naqvi et al. and Kimura et al., who demonstrated that apparent EF reductions largely reflect geometric and load-dependent factors rather than impaired myocardial contractility28,31. Advanced imaging studies, including strain-based analysis, have further confirmed that intrinsic myocardial function remains preserved throughout gestation despite volumetric changes28,32,33.

The parallel increases in aortic and pulmonary arterial flow velocities and pressure gradients observed in this study support a coordinated systemic and pulmonary vascular adaptation that maintains hemodynamic equilibrium as cardiac output rises. These changes are in agreement with physiologic observations by Soma-Pillay et al. and Mahendru et al., who reported that arterial compliance and vasodilation enable the circulation to accommodate elevated blood volume without pathologic pressure loading. Thus, the systolic changes demonstrated here represent a reversible physiologic adaptation rather than a marker of early dysfunction24,25.

Left ventricular diastolic function and hemodynamics

This study demonstrated trimester-dependent alterations in left ventricular (LV) diastolic function consistent with physiologic maternal cardiovascular adaptations during normal pregnancy. The observed pattern—mild declines in the E/A ratio, progressive reductions in early diastolic myocardial velocities (e′), modest increases in late diastolic velocities (a′), and slight rises in E/e′—reflects load-dependent modulation of ventricular relaxation rather than diastolic dysfunction. These findings are in line with previous longitudinal and meta-analytic studies12,25,26,31.

Gestational increases in plasma volume and venous return elevate LV filling pressures and preload, influencing transmitral and tissue Doppler velocities. Reductions in e′ and e′/a′ ratios likely reflect enhanced chamber compliance and altered myocardial relaxation secondary to volume expansion and neurohormonal modulation2,24,25. Importantly, the modest rise in E/e′ suggests preserved filling pressures, confirming the physiologic and reversible nature of these changes. Similar observations were reported by Kimura et al., who noted transient late-pregnancy reductions in e′ and e′/a′ that normalized postpartum31, and by de Haas et al., whose meta-analysis confirmed consistent e′ declines in healthy pregnancies26.

These results also support the concept proposed by Melchiorre et al., in which maternal cardiovascular adaptation balances chronic volume overload with ventricular compliance, and mild attenuation of relaxation indices represents an adaptive rather than maladaptive process12. The absence of a disproportionate rise in E/e′ or left atrial pressure elevation indicates maintained ventricular compliance despite increased circulating volume.

Collectively, these findings indicate that gestational changes in LV diastolic indices among Chinese women reflect a normal adaptive response to altered loading conditions. Such diastolic modulation facilitates increased cardiac output while preserving ventricular filling efficiency. Future studies using speckle-tracking strain or 3D echocardiography could clarify the relative contributions of myocardial relaxation, preload, and afterload to these dynamic changes in pregnancy.

Ascending aorta and main pulmonary artery hemodynamics

The observed gestational variations in ascending aortic (AO) and main pulmonary artery (PA) hemodynamics reflect the physiologic cardiovascular adaptation that accompanies the progressive increase in blood volume and cardiac output during normal pregnancy. Although both AO and PA flow velocities and pressure gradients demonstrated mild upward trends, all parameters remained within normal reference ranges, supporting the interpretation that these changes represent load-dependent modulation rather than pathologic alteration. The modest increases in AO and PA velocities and pressure gradients are likely a result of elevated stroke volume and augmented flow through compliant great vessels, consistent with the global cardiovascular adaptations of pregnancy2,24,25.

The balanced enhancement of aortic and pulmonary arterial flow observed in this study highlights the coordinated systemic and pulmonary circulation adjustment necessary to maintain hemodynamic equilibrium. As plasma volume expands and systemic vascular resistance declines, the maternal cardiovascular system compensates by increasing cardiac output and arterial distensibility, thereby maintaining efficient tissue perfusion2,25. This is supported by Soma-Pillay et al., who described a substantial reduction in systemic vascular tone and a parallel increase in vascular compliance as hallmark features of mid-to-late pregnancy adaptation25.

The absence of disproportionate elevation in aortic gradients or pulmonary pressures further distinguishes these physiologic changes from early manifestations of hypertensive or pulmonary vascular disorders. Mahendru et al. and Melchiorre et al. both reported that in uncomplicated pregnancies, the aortic and pulmonary arterial systems undergo transient and reversible remodeling without evidence of structural or functional compromise12,24. These findings underscore the adaptability of the great vessels under the influence of hormonal factors—particularly estrogen and relaxin, which promote endothelial nitric oxide synthesis, vasodilation, and extracellular matrix remodeling, leading to decreased arterial stiffness and enhanced compliance2,24,25.

Strengths and limitations

Strengths

  1. 1.

    Comprehensive characterization across trimesters: This study systematically assessed maternal cardiac morphology, systolic and diastolic function, and great artery hemodynamics throughout all three trimesters, providing a complete depiction of gestational cardiovascular adaptation.

  2. 2.

    Large, well-defined cohort: The inclusion of 412 healthy Chinese women with singleton pregnancies represents, ensuring robust statistical power and reliable trimester-specific reference values.

  3. 3.

    Standardized echocardiographic protocol: All measurements were performed by a single board-certified sonographer using guideline-based methods and consistent equipment, minimizing inter-observer variability and enhancing reproducibility.

  4. 4.

    Ethnicity-specific reference establishment: The study addresses a significant research gap by providing normative echocardiographic reference ranges specific to Chinese women, facilitating improved diagnostic precision and cross-ethnic comparisons in maternal cardiovascular assessment.

Limitations

  1. 1.

    Cross-sectional rather than longitudinal design: Because our hospital primarily manages acute and critical cases, low-risk pregnant women do not routinely return for scheduled follow-up examinations. As a result, longitudinal imaging across gestational stages was not feasible, and each trimester group consisted of different participants. This inter-individual design limits the ability to interpret true temporal changes within the same subjects.

  2. 2.

    Single-center study population: The findings may have limited generalizability to other regions or ethnic groups within China due to potential genetic and environmental differences. Moreover, the smaller sample size in the first trimester (n = 19) reflects real-world clinical practice at our institution, a regional tertiary referral center focused on acute and high-risk obstetric care, where low-risk women in early pregnancy usually receive routine antenatal assessments at community hospitals or local clinics rather than at our center.

  3. 3.

    Absence of postpartum follow-up: Postpartum echocardiographic evaluation was not performed in the present study. Previous literature indicates that certain cardiac structural and functional adaptations may be most pronounced during the early postpartum period, particularly within the first week after delivery, rather than during late pregnancy2,34. According to our hospital’s routine practice, patients who underwent normal spontaneous delivery (NSD) were typically discharged after 2 days, whereas those who underwent cesarean section (C/S) were discharged after 5 days. Consequently, most participants returned home shortly after delivery, limiting the feasibility of standardized early postpartum echocardiographic assessment. The absence of these early postpartum data restricts our ability to determine the maximal extent and subsequent resolution of gestational cardiac remodeling. Future longitudinal studies incorporating systematic echocardiographic follow-up during the early postpartum period are warranted to more comprehensively delineate the temporal trajectory of maternal cardiovascular adaptation.

  4. 4.

    Limited advanced imaging parameters: Owing to manpower limitations, the speckle-tracking or 3D echocardiographic analyses were not incorporated, which could provide additional insights into myocardial strain and subclinical functional changes.

Conclusion

This study delineates the physiological adaptations of the maternal cardiovascular system during normal pregnancy in healthy Chinese women. Progressive ventricular remodeling, increased stroke volume and cardiac output, and coordinated diastolic and vascular adaptations collectively support uteroplacental perfusion while preserving myocardial function. The establishment of trimester-specific echocardiographic reference values provides a robust framework for ethnicity-specific cardiovascular assessment, facilitates early identification of abnormal adaptation, and enhances maternal cardiovascular risk stratification. By addressing the limitations of applying non-ethnicity-specific normative standards, these findings contribute clinically relevant insights. Future longitudinal and advanced imaging studies are warranted to further elucidate temporal dynamics, interethnic variability, and the mechanisms underlying maternal cardiac adaptation.