Authors: Vincenzo Pota, Francesco Coppolino, Marco Fiore, Francesca Piccialli, Luca Gregorio Giaccari, Maria Beatrice Passavanti, Maria Caterina Pace, Pasquale Sansone
Categories: Research, Maternal acute kidney injury, Renal replacement therapy, Critical care obstetrics
Source: Journal of Anesthesia, Analgesia and Critical Care
Authors: Vincenzo Pota, Francesco Coppolino, Marco Fiore, Francesca Piccialli, Luca Gregorio Giaccari, Maria Beatrice Passavanti, Maria Caterina Pace, Pasquale Sansone
Maternal acute kidney injury (AKI) represents a severe and preventable complication of pregnancy, contributing significantly to maternal and perinatal morbidity and mortality worldwide. Marked disparities persist between low- and middle-income countries (LMICs) and high-income countries (HICs), particularly regarding access to renal replacement therapy (RRT) and critical care support. We aimed to estimate the global incidence among obstetric ICU admissions, risk factors, and outcomes of maternal AKI requiring intensive care, with a specific focus on the burden and prognostic impact of RRT.
This systematic review and meta-analysis followed the PRISMA 2020 guidelines. PubMed, Embase, Scopus, and Web of Science were searched up to April 2025 for original studies reporting incidence, etiology, and outcomes of maternal AKI in intensive care units (ICUs). Random-effects models were used to pool incidence rates and outcome measures across studies.
Eleven studies comprising 3,494 critically ill obstetric patients from seven countries were included. The pooled global incidence of maternal AKI was 2,813 per 10,000 obstetric ICU admissions (95% CI: 1,5–4,5), with the highest rates in African (5,909/10,000) and Western Pacific (2,912/10,000) regions. The predominant etiologies were hypertensive disorders of pregnancy (including HELLP syndrome), obstetric hemorrhage, and sepsis. Among AKI patients, 20.4% required RRT (95% CI: 11.7–33.2), and mortality was 19.4% (95% CI: 12.3–29.2). Renal recovery occurred in 81.8%, while persistent dysfunction was observed in 18.2% of survivors. A strong correlation was found between RRT use and mortality (Spearman’s ρ = 0.71, p = 0.047).
Among obstetric patients admitted to intensive care units, maternal AKI represents a substantial clinical burden, with a significant proportion of affected women requiring RRT—a marker of disease severity strongly associated with increased mortality. Despite generally favorable renal recovery among survivors, profound regional disparities persist. These estimates apply exclusively to obstetric ICU admissions and should not be extrapolated to the general pregnant population. Early identification, standardized diagnostic criteria, and equitable access to renal replacement therapies remain critical priorities to improve maternal outcomes in intensive care settings.
The online version contains supplementary material available at 10.1186/s44158-026-00353-3.
Acute kidney injury (AKI) in pregnancy remains a major global health challenge, with a marked disparity in incidence and outcomes between low- and middle-income countries (LMICs) and high-income countries (HICs). In LMICs, pregnancy-associated AKI (PrAKI) is significantly more prevalent and is associated with high rates of maternal morbidity and mortality, primarily due to limited access to antenatal care, delayed referrals, and inadequate resources for managing obstetric complications. The leading aetiologies in these settings are preeclampsia/eclampsia, haemorrhage, and sepsis [1–3]. Meta-analyses estimate the incidence in LMICs at approximately 91 cases per 10,000 pregnancies, with maternal case fatality rates around 10.8% and adverse fetal outcomes (stillbirth or neonatal death) in nearly 30% of cases [1]. Maternal mortality rates in single-center studies can be even higher, up to 24% [2].
In contrast, HICs have seen a historical decline in PrAKI incidence due to improvements in obstetric care, access to intensive care, and better management of hypertensive disorders. However, recent data indicate a re-emergence of PrAKI in HICs, attributed to increasing maternal age, higher prevalence of comorbidities, and more frequent obstetric interventions [4–6]. The incidence in HICs is much lower (1.0–2.8%), but PrAKI still carries significant risk for both maternal and fetal morbidity [4, 7, 8].
Hypertensive disorders of pregnancy—including preeclampsia and eclampsia—remain the most common cause of maternal acute kidney injury (AKI) globally, with additional contributions from thrombotic microangiopathies (such as HELLP syndrome and atypical haemolytic uremic syndrome) and acute fatty liver of pregnancy, which are increasingly recognized in both high- and low-resource settings [4, 6, 8–11].
The burden and etiological spectrum of maternal AKI vary substantially by region.
In South Asia, sepsis, preeclampsia, and obstetric haemorrhage are the leading causes, and progression to advanced Kidney Disease: Improving Global Outcomes (KDIGO) stages is common, with high rates of maternal and fetal mortality [1, 2, 12]. In African cohorts, hypertensive disorders and sepsis predominate, with a substantial proportion of cases requiring renal replacement therapy and maternal mortality rates ranging from 0 to 34% [1, 13, 14]. In North Africa and the Middle East, HELLP syndrome and postpartum haemorrhage are major aetiologies [1, 8]. In Latin America, the incidence of AKI is lower, but the need for renal replacement therapy is strongly associated with adverse outcomes [6, 15].
Maternal AKI is associated with severe clinical maternal mortality rates in low-resource settings range from 10 to 24%, and perinatal mortality is also high [1, 2, 13, 15]. Even in high-income countries, AKI increases the risk of multiorgan failure, cesarean delivery, and adverse fetal outcomes [6, 9, 10, 15]. Renal recovery is achieved in most survivors, but persistent renal dysfunction or progression to chronic kidney disease occurs in a subset [12, 13, 15]. The requirement for renal replacement therapy is a strong predictor of mortality and poor outcomes [1, 2, 15].
Early identification, multidisciplinary management, and addressing region-specific aetiologies are essential to improve maternal and fetal outcomes, as emphasized by the 32nd Acute Disease Quality Initiative Workgroup [9].
This underscores the close relationship between disease severity, healthcare resource availability, and patient outcomes. Despite advances, there is still no comprehensive global synthesis quantifying the incidence of maternal AKI, its staging, use of RRT, and outcomes across world regions.
Therefore, we conducted a systematic review and meta-analysis to estimate the global incidence of maternal AKI among critically ill obstetric patients, to examine its aetiologies, and to quantify the burden of RRT use, renal recovery, and mortality across different geographic settings.
This systematic review and meta-analysis was not prospectively registered in PROSPERO. However, the review was conducted according to PRISMA 2020 guidelines, with predefined eligibility criteria and transparent reporting of methods.
A comprehensive literature search was performed on April 19, 2025, across PubMed, Embase, Scopus, and Web of Science. The search strategy combined the following terms and Boolean “acute kidney injury” OR “AKI”, “renal replacement therapy” OR “RRT”, “incidence” OR “epidemiology”, “pregnancy”, and “pregnancy complications”.
The full search strings for each database are reported in Supplementary Table S1.
The screening process was independently conducted by two reviewers. All records were imported into Rayyan QCRI, where duplicates were identified and removed. Full texts were assessed for eligibility based on predefined inclusion and exclusion criteria. Discrepancies were resolved by consensus with a third senior author.
Studies were included if Reported data on the incidence of maternal AKI and/or the use of RRT in the intensive care unit (ICU);Provided original data from cohort, cross-sectional, or case–control studies;Reported sufficient information to estimate incidence rates.
There were no restrictions on maternal age or language.
Exclusion criteria Case reports, case series, reviews, or in vitro/in vivo studies;Studies reporting neonatal AKI only;Studies focusing exclusively on risk factors without incidence data;Duplicates, with preference for the most complete dataset.
All statistical analyses were conducted using a random-effects model to account for expected heterogeneity across study populations, diagnostic definitions, and healthcare settings. Pooled estimates of incidence and outcome proportions were calculated using the DerSimonian–Laird method with 95% confidence intervals (CIs). When reported, data were transformed using the Freeman–Tukey double arcsine transformation to stabilize variances. Heterogeneity was quantified using the Cochran Q statistic and the I2 index, with values of 25%, 50%, and 75% interpreted as low, moderate, and high heterogeneity, respectively. Leave-one-out sensitivity analyses were performed on the transformed scale used for the primary meta-analysis, with pooled estimates subsequently back-transformed to the original proportion scale for graphical display and interpretation. Publication bias was evaluated by visual inspection of funnel plots and tested quantitatively using Egger’s regression intercept. Correlation analyses between the proportion of patients requiring renal replacement therapy (RRT) and outcome variables (mortality and renal recovery) were performed using Spearman’s rank correlation coefficient (ρ). Statistical significance was set at a p-value < 0.05 for all tests.
For quantitative pooling of incidence, only studies reporting maternal AKI incidence using obstetric ICU admissions as the denominator were included. Incidence was standardized and expressed per 10,000 obstetric ICU admissions. Studies reporting incidence per pregnancies or per hospital admissions were not converted and were excluded from pooled incidence analyses due to non-comparable denominators.
Given the limited number of included studies and the inconsistent reporting of key clinical covariates, meta-regression and additional subgroup analyses beyond WHO regions were not performed, as they would have been underpowered and potentially misleading.
Subgroup or sensitivity analyses stratified by AKI diagnostic definition (KDIGO, RIFLE, AKIN, or non-standard clinical criteria) were considered but not performed due to the limited number of studies within each category and heterogeneity in the operational application of diagnostic criteria, which would have rendered such analyses underpowered and potentially misleading.
The search yielded a total of 206 records (PubMed: 74; Embase: 129; Scopus: 3; Web of Science: 0). After removing 42 duplicates, 164 records remained for screening. Following title and abstract assessment, 50 full-text articles were evaluated for eligibility according to predefined inclusion and exclusion criteria. Of these, 39 articles were excluded. Finally, 11 studies were included in the quantitative synthesis (Fig. 1).Fig. 1PRISMA 2020 flow diagram illustrating the study selection process
Collectively, the 11 included studies provided data on approximately 3,500 critically ill pregnant women admitted to obstetric or general ICUs across seven countries. [16–26] The African region (Kenya, Morocco, Egypt) and South-East Asia (Sri Lanka, India) were the most represented, with three studies each. The Western Pacific region (China) contributed two records, while Latin America (Brazil), Europe (France), and North Africa/Middle East (Tunisia) were each represented by a single-country study.
The data collection periods spanned from 1995 to 2023, with publication years ranging between 2004 and 2025, thereby capturing both historical and contemporary cohorts of obstetric ICU patients. Diagnostic definitions of AKI were five studies employed standardized criteria (KDIGO, RIFLE, or AKIN), while the others relied on local definitions or clinical diagnosis of acute renal failure [27].
All 11 studies reported raw incidence data of maternal AKI, and several additionally described risk factors (including preeclampsia, haemorrhage, sepsis, and caesarean delivery) and the use of renal replacement therapy. The risk of bias assessment, performed using the Joanna Briggs Institute (JBI) checklist, indicated that six studies had a moderate risk of bias, three a low risk, and two were classified as high risk (Table S2).
Table 1 summarises the cumulative incidence per 10,000 obstetric ICU admissions globally and by study setting. Table 1Characteristics of included studies on maternal AKIAuthor (Year)CountryDesignPopulation (n)AKI Cases (n)Incidence (%)CriteriaRRT (n,%)Mortality (%)Main risk factorsBouaziz (2013) [16]TunisiaRetrospective (1995–2011)55031356.9Not reported89.3 (vs 1.7 no AKI)Preeclampsia (66.5%), obstetric hemorrhage (27.8%)De Silva (2017) [17]BrazilCross-sectional (2012–2014)3899224AKINNot reported21 (with AKI)Cesarean delivery, thrombocytopeniaFerreira (2020) [18]BrazilRetrospective (2014–2016)61917227.8KDIGO7.68.7 (higher in KDIGO 2–3)Shock (hypovolemic, septic), high APACHE II/SOFASuri (2024) [20]IndiaRetrospective (2017–2019)27501716.21 (of CCU admissions)Not reported37.4 ~ 33Obstetric hemorrhage, sepsis (39%), preeclampsia (23.4%)Kamal (2014) [21]EgyptProspective (2008–2010)510305.9 (ICU obstetric)RIFLENot reported31HELLP (43%), hypertension (30%), puerperal sepsis (10%), abruptio placentae (6.6%)Mjahed (2004) [22]MoroccoProspective1784625.8Non-standardized clinical definition32.632.6 (with AKI)DIC, HELLP, abruption placentae, neurological complicationsSong (2024) [23]ChinaRetrospective (2014–2020)87413615.6KDIGO47.7Not reportedShock, sepsis, coagulopathy, hemorrhage, liver failure, IUFDTyagi (2021) [24]IndiaProspective1632515.3Not reported828 (with AKI)Sepsis, shock, anemiaNg’ethe (2025) [25]KenyaRetrospective (2020–2023)1784625.8KDIGO32.632.6Hypertensive disorders (64.1%), hemorrhage (38.4%), sepsis (36.5%)Summary of the observational studies included in the systematic review and meta-analysis, reporting study design, diagnostic criteria, population size, incidence, use of renal replacement therapy (RRT), mortality, and main associated risk factors
The pooled global incidence estimates therefore apply specifically to critically ill obstetric patients admitted to intensive care units and should not be extrapolated to the general pregnant population. Across 11 datasets including approximately 3,494 critically ill pregnant women, the pooled global incidence of maternal AKI was 2,813 per 10,000 obstetric ICU admissions (95% CI: 1,546–4,559) (Fig. 2). Leave-one-out sensitivity analysis showed that the pooled incidence estimate remained stable after sequential exclusion of individual studies. All leave-one-out estimates were calculated on the transformed scale used for the primary analysis and are presented on the original proportion scale. The red dashed line represents the overall pooled estimate derived from the full model including all studies. Substantial heterogeneity was observed (Q = 1,107.45; I2 = 99.1%), largely reflecting variability in study design, sample size, and diagnostic definitions of AKI (KDIGO, RIFLE, AKIN, or clinical criteria). The pooled global incidence estimates should be interpreted with caution, as extreme heterogeneity reflects substantial differences in study populations, diagnostic criteria, and healthcare settings. Diagnostic definitions of AKI varied substantially across studies. Only a subset applied standardized criteria (KDIGO, RIFLE, or AKIN), while others relied on local or clinical definitions, contributing to between-study heterogeneity in reported incidence and outcomes. Analyses of AKI severity according to KDIGO staging were restricted to studies that explicitly reported KDIGO stages or provided data convertible to KDIGO classification. Studies relying solely on non-standardized clinical definitions were not included in pooled staging analyses.Fig. 2Forest plot showing the pooled global incidence of maternal acute kidney injury (AKI)
Visual inspection of the funnel plot and Egger’s regression test did not indicate clear evidence of publication bias. However, given the limited number of included studies and the substantial heterogeneity across pooled estimates, both visual and statistical assessments have limited power and should be interpreted with caution. (bias intercept = 32.87; p = 0.528) (Supplementary Fig. S1). Leave-one-out sensitivity analysis supported the robustness of the pooled estimate, which consistently ranged between 2,406 and 3,193 per 10,000 across replications (Supplementary Fig. S2).
Stratified analyses according to WHO regions revealed marked disparities. The highest pooled incidence was observed in the African region, reported at 5,909 per 10,000 (95% CI: 4,576–7,120) based on a single Kenyan study. The Western Pacific region (China) showed a pooled incidence of 2,912 per 10,000 (95% CI: 778–6,666) across two datasets, while the South-East Asia region (India) reported an incidence of 979 per 10,000 (95% CI: 385–2,273) based on two records. The group of studies classified as Other regions, which included North African, Middle Eastern, and Latin American cohorts, yielded a pooled incidence of 3,226 per 10,000 (95% CI: 1,628–5,382), also based on six datasets (Table 2, Fig. 3).These findings underscore substantial regional heterogeneity, with the highest incidence of maternal AKI reported in African ICUs, the lowest in South-East Asia, and intermediate but variable rates in Latin American, Middle Eastern, and European cohorts. Table 2Stratified incidence of maternal AKI by WHO regionsWHO RegionNo. of studiesPooled incidence per 10,00095% CI (Low)95% CI (High)Africa15909.14576.57120.3Other63225.61628.25382.4South-East Asia2978.6384.72272.7Western Pacific22912.0778.46666.2Summary of subgroup analyses reporting the pooled incidence of maternal acute kidney injury (AKI) per 10,000 obstetric ICU admissions, stratified by WHO regions. Incidence estimates are presented with 95% confidence intervalsFig. 3Regional stratification of maternal AKI incidence across WHO regions
Across the included studies, maternal AKI was consistently multifactorial, with hypertensive disorders of pregnancy, haemorrhage, and sepsis emerging as the dominant contributors. Hypertensive disorders—including preeclampsia/eclampsia and HELLP syndrome—were among the most frequent precipitants across African and Asian cohorts. In North African series (e.g., Egypt and Morocco), HELLP accounted for a large share of AKI cases (reported up to ~ 40–45% in some datasets), while in the Kenyan ICU cohort, hypertensive disorders were present in approximately half or more of AKI cases. Haemorrhagic complications were recurrently postpartum haemorrhage (PPH) and placental abruption were reported in North African and South Asian cohorts (e.g., Tunisia and India), contributing roughly a quarter to one-third of cases where specified. Sepsis was another consistent determinant, reported in at least six studies, with frequencies typically ranging from ~ 10% in some Egyptian datasets to ~ 30–40% in Indian and Chinese cohorts. Coagulopathy/DIC was repeatedly noted as an aggravating factor, particularly in Moroccan and Chinese series.
Additional contributors varied by setting and severity shock (hypovolaemic and septic), respiratory failure, and anaemia were more prominent in Indian and Chinese ICU cohorts; caesarean delivery and thrombocytopenia were associated with AKI in the Brazilian cross-sectional study. Less frequent but noteworthy factors—each highlighted in single reports—included intrauterine fetal death (IUFD), hepatic dysfunction, and bladder injury.
Taken together, the evidence underscores a triad—hypertensive disorders (including HELLP), major haemorrhage (PPH/abruption), and sepsis—as the predominant risk constellation for maternal AKI across regions, with coagulopathy/DIC and shock often compounding severity. A study-level summary of reported risk factors is provided in Table 3, and their cross-study frequencies are synthesised in Fig. 4. Table 3Risk factors associated with maternal AKIAuthor (Year)CountryMain risk factorsBouaziz (2013) [16]TunisiaPreeclampsia (66.5%), obstetric hemorrhage (27.8%)De Silva (2017) [17]BrazilCesarean delivery, thrombocytopeniaFerreira (2020) [18]BrazilShock (hypovolemic, septic), high APACHE II/SOFA scoresSuri (2024) [20]IndiaObstetric hemorrhage (placental abruption, PPH), sepsis (39%), preeclampsia (23.4%)Kamal (2014) [21]EgyptHELLP (43%), hypertension (30%), puerperal sepsis (10%), abruptio placentae (6.6%)Mjahed (2004) [22]MoroccoDIC, HELLP, neurological complications, abruptio placentaeSong (2024) [23]ChinaShock, sepsis, coagulopathy, hemorrhage, liver failure, IUFD, ventilationTyagi (2021) [24]IndiaSepsis, shock, anemiaNg’ethe (2025) [25]KenyaHypertensive disorders (64.1%), obstetric hemorrhage (38.4%), sepsis (36.5%)Reported risk factors for maternal acute kidney injury (AKI) in the included studies. Data highlight the multifactorial nature of AKI, with hypertensive disorders of pregnancy, hemorrhagic complications, and sepsis emerging as the most consistent contributors across different settingsFig. 4Distribution of etiological factors associated with maternal AKI
Among the included studies, the pooled analysis demonstrated that approximately one in five women with AKI required renal replacement therapy (RRT), with a cumulative incidence of 20.4% (95% CI: 11.7–33.2; k = 9). Considerable heterogeneity was observed across studies (I2 = 94.1%), largely reflecting differences in access to dialysis and ICU resources across regions (Fig. 5). Similarly, mortality among obstetric patients with AKI was high, with a pooled estimate of 19.4% (95% CI: 12.3–29.2; k = 10; I2 = 89.3%) (Fig. 6). Mortality exceeded 25% in African and South Asian cohorts (pooled estimates with overlapping confidence intervals), compared with lower pooled mortality in European and Latin American studies (< 10%). When renal recovery was specifically reported, the pooled rate of renal function recovery was 81.8% (95% CI: 67.5–90.7; k = 6), while the rate of persistent renal dysfunction or non-recovery was 18.2% (95% CI: 9.3–32.5). Both endpoints showed substantial heterogeneity (I2 ≈ 90%) (Fig. 7). Stratification by KDIGO stage revealed that stage 1 accounted for 42.1% (95% CI: 23.6–63.1), stage 2 for 28.9% (95% CI: 22.4–36.4), and stage 3 for 26.8% (95% CI: 14.9–43.4) of maternal AKI cases. Stage 1 displayed the widest variability (I2 = 95.2%), while stage 2 showed a more consistent distribution (I2 = 67.6%) (Fig. 8). Taken together, these findings highlight the substantial burden of severe AKI in the obstetric ICU population, with up to one in five patients requiring dialysis and nearly one in five dying during hospitalization. Despite a generally high probability of renal recovery, the variability in staging and outcomes across settings underscores the influence of diagnostic criteria, clinical management, and healthcare resources on maternal AKI prognosis. The analysis of correlations revealed that the need for renal replacement therapy (RRT) was strongly associated with mortality in women with maternal AKI. A strong positive association was observed between the proportion of patients requiring renal replacement therapy and reported mortality across studies (Spearman’s ρ = 0.71, p = 0.047). This study-level correlation suggests that cohorts with a higher need for RRT tend to report higher mortality rates. In contrast, the association between RRT use and renal non-recovery showed a positive but non-significant trend (Spearman’s ρ = 0.70, p = 0.188). Overall, these findings suggest that the requirement for RRT may represent a marker of disease severity and is closely linked with adverse outcomes, particularly increased maternal mortality (Fig. 9).Fig. 5Pooled proportion of obstetric ICU patients with AKI requiring renal replacement therapy (RRT)Fig. 6Forest plot of maternal mortality among critically ill women with AKIFig. 7Pooled rates of renal recovery and persistent renal dysfunction among survivors of maternal AKIFig. 8Distribution of maternal AKI severity according to KDIGO staging (1–3)Fig. 9Correlation between renal replacement therapy (RRT) use and adverse outcomes
Our systematic review and meta-analysis provides the most comprehensive synthesis to date on the global burden, risk factors, and outcomes of maternal acute kidney injury (AKI) in intensive care units (ICUs). It is important to emphasize that all incidence estimates reported in this study refer specifically to obstetric patients admitted to intensive care units. As the analysis was restricted to ICU-based cohorts, extrapolation of these findings to the general pregnant population is not appropriate. The term “global incidence” is therefore used to describe the worldwide burden of maternal AKI within the obstetric ICU setting, rather than population-level pregnancy incidence.
Across 11 studies including almost 3,500 critically ill women, we observed that maternal AKI occurred in a substantial proportion of obstetric ICU admissions, with a global pooled incidence of nearly 28% (2,813 per 10,000 admissions; 95% CI: 1,546–4,559). An important limitation is the heterogeneity of incidence denominators across studies. By restricting pooled analyses to ICU-based denominators, we ensured internal consistency but limited generalizability. Studies reporting incidence per pregnancies or hospital admissions were excluded from quantitative pooling to avoid inappropriate standardization, underscoring the need for harmonized reporting of maternal AKI epidemiology across clinical settings.
The very high heterogeneity observed across most pooled outcomes—particularly for maternal AKI incidence—substantially limits the interpretability of single summary estimates. This heterogeneity is driven by genuine clinical and contextual differences, including variability in AKI definitions, study design, case-mix severity, ICU admission criteria, access to renal replacement therapy, and temporal changes in obstetric and critical care practices. In this context, pooled estimates should be interpreted as global descriptive indicators of burden and dispersion rather than precise effect sizes applicable to individual settings. Importantly, the magnitude of heterogeneity itself highlights profound regional disparities and underscores the need for standardized diagnostic definitions and improved reporting in maternal critical care research.
Importantly, a relevant proportion of women with maternal AKI required renal replacement therapy (RRT) 20.4% (95% CI: 11.7–33.2), and mortality remained high, approaching 19.4% (95% CI: 12.3–29.2) overall. Despite high rates of renal recovery among survivors, persistent dysfunction occurred in nearly one in five cases, underscoring the long-term burden of maternal AKI.
Our findings confirm marked disparities in the incidence of maternal AKI across world regions [4, 15, 18, 28].
There are pronounced regional differences in the incidence, aetiologies, and outcomes of maternal acute kidney injury (AKI) in obstetric ICU admissions.
In African and South Asian cohorts, the incidence of maternal AKI is substantially higher, with pooled rates ranging from 7.6% to 26% in hospital-based studies, and up to 254 per 10,000 pregnancies in population-based meta-analyses. The leading causes are preeclampsia/eclampsia, HELLP syndrome, obstetric haemorrhage, and sepsis. These aetiologies often present in combination, and late presentation, limited access to antenatal care, and delayed referral contribute to the high burden. Maternal mortality rates in these regions range from 10 to 34%, and perinatal mortality is also elevated, with up to 45% fetal death in some cohorts. Renal replacement therapy is frequently required, and persistent renal dysfunction is common among survivors [1, 2, 13, 14, 29].
In high-income countries such as France and China, the incidence of maternal AKI is lower (typically 1–2.8% of obstetric ICU admissions), but significant morbidity persists. Here, older maternal age, pre-existing comorbidities, and increased rates of obstetric interventions (e.g., cesarean delivery, assisted reproduction) are important risk factors. While hypertensive disorders and HELLP syndrome remain relevant, the spectrum of causes is broader, and outcomes are generally better due to earlier recognition and more advanced supportive care. However, maternal AKI is still associated with increased risk of multiorgan failure, adverse fetal outcomes, and incomplete renal recovery [4, 8, 10, 15, 30].
These findings are consistent with the World Health Organization–led meta-analysis, which demonstrates that pregnancy-related AKI remains disproportionately more frequent in low- and middle-income countries, with maternal mortality rates ranging from 10 to 28% and a strong association with adverse fetal outcomes. The meta-analysis highlights the need for improved prevention, timely diagnosis, and expanded access to antenatal and critical care services to reduce the global burden [1].
The risk profile of maternal AKI across studies was multifactorial, with a triad of hypertensive disorders, haemorrhage, and sepsis consistently identified as leading contributors. Hypertensive disorders—including preeclampsia, eclampsia, and HELLP syndrome—were dominant in North African and South Asian cohorts, accounting for nearly half of AKI cases in some reports [16, 20]. Haemorrhagic complications, particularly postpartum haemorrhage and placental abruption, were prominent in Tunisian, Indian, and Brazilian studies [18]. Sepsis, often linked to delayed diagnosis or limited antibiotic access, was reported in six of the included studies, with frequencies ranging from 10% in Egypt to nearly 40% in Indian and Chinese cohorts [19, 23]. Coagulopathy and disseminated intravascular coagulation (DIC) further aggravated outcomes, especially in Moroccan and Chinese patients [22, 23]. These multifactorial patterns are consistent with global epidemiological reviews of AKI in critical illness, which emphasize sepsis, hypovolemia, and shock as universal pathways to renal failure [31].
The requirement for RRT emerged as a crucial marker of severity. In our pooled analysis, 20.4% of maternal AKI patients required dialysis, and the proportion of RRT use correlated strongly with higher mortality across cohorts (ρ = 0.71, p = 0.047). The observed association between RRT use and mortality should be interpreted with caution. This correlation was assessed at the study level, without adjustment for individual patient characteristics, disease severity, or healthcare resource availability. As such, RRT use should be regarded primarily as a marker of severe disease rather than an independent causal predictor of mortality. The possibility of ecological fallacy must be acknowledged, as associations observed in aggregated data may not reflect patient-level relationships. Nonetheless, the consistency of this association across heterogeneous cohorts underscores the prognostic relevance of dialysis-requiring AKI in critically ill obstetric populations. This finding reinforces prior single-center studies from Brazil, India, and Kenya, where dialysis-requiring AKI was consistently associated with a sharp rise in mortality [18, 24, 25]. Mortality exceeded 25% in African and South Asian cohorts (pooled estimates with overlapping confidence intervals), compared with lower pooled mortality in European and Latin American studies (< 10%) [18, 19].
Indian studies similarly report that up to 20% of maternal AKI cases require RRT, and these patients have markedly elevated mortality, with rates approaching 33% in those progressing to advanced KDIGO stages and requiring dialysis [32].
Kenyan and broader African data show that maternal AKI requiring RRT is associated with mortality rates ranging from 10 to 34%, with the highest burden in sub-Saharan Africa [1, 14].
Comparatively, African and South Asian cohorts have the highest incidence of RRT requirement and mortality, reflecting the persistence of preventable etiologies and limited access to critical care. European and Latin American cohorts report lower overall incidence, but RRT remains a strong predictor of poor outcome, with in-hospital mortality for AKI patients requiring RRT in Latin America at 26.5% [33, 34].
Despite this, the majority of survivors achieved renal recovery, with pooled rates above 80%, although up to 20% of women developed persistent dysfunction, highlighting the risk of progression to chronic kidney disease [21, 35]. Rates of renal recovery among survivors range from 53 to 90% in African studies, with persistent dysfunction or progression to chronic kidney disease in 10–33% of cases [14, 32]. In Brazilian and Indian cohorts, complete recovery is less frequent in obstetric AKI than in non-obstetric AKI, and dialysis dependency or CKD progression is more common in those with severe AKI [32].
Stratification by KDIGO stage confirmed that severe forms (stage 2–3) accounted for more than half of reported cases, a distribution consistent with the high RRT requirement.
Extreme heterogeneity across pooled estimates, particularly for maternal AKI incidence, substantially limits the interpretability of single summary estimates. Although the risk of bias assessment was systematically conducted using the Joanna Briggs Institute checklist, it is important to consider how study quality may have influenced the interpretation of pooled estimates. Several included studies were classified as having a moderate or high risk of bias, primarily due to retrospective designs, heterogeneous or non-standardized AKI definitions, and limited adjustment for confounding factors.
The inclusion of such studies may have contributed to the substantial heterogeneity observed across most analyses and may have influenced pooled incidence and outcome estimates. Consequently, results should be interpreted as global descriptive indicators of burden rather than precise or causal effect sizes. Sensitivity analyses stratified by risk of bias were not performed because of the limited number of studies and the risk of generating underpowered or misleading subgroup estimates.
A major contributor is the variability in AKI diagnostic definitions, as only a minority of studies consistently applied standardized KDIGO, RIFLE, or AKIN criteria, while others relied on non-standardized clinical judgment. Such variability may bias incidence estimates—potentially inflating rates in settings with broader clinical definitions or underestimating severity where biochemical monitoring is limited—and may distort severity distributions. Although KDIGO stage analyses were restricted to studies using standardized or convertible definitions, residual heterogeneity remains, reflecting differences in case-mix severity, timing of diagnosis, and healthcare resources. In this context, pooled estimates should be interpreted as global descriptive indicators rather than precise effect sizes, and the magnitude of heterogeneity itself highlights the urgent need for standardized diagnostic definitions and reporting in maternal critical care research.
Assessment of publication bias represents an additional limitation of this meta-analysis. Although funnel plot inspection and Egger’s test did not reveal clear asymmetry, the small number of included studies and the extreme between-study heterogeneity substantially limit the reliability and interpretability of both visual and statistical methods for detecting publication bias.
A further limitation is the lack of prospective registration of the review protocol (e.g., in PROSPERO). Although prospective registration is encouraged to enhance transparency, it is not mandatory for systematic reviews of observational epidemiological studies. Importantly, the review was conducted in accordance with PRISMA 2020 guidelines, with predefined eligibility criteria, comprehensive search strategies, and transparent reporting, which mitigates the risk of selective reporting.
This systematic review and meta-analysis provides the most comprehensive synthesis to date on the global incidence and outcomes of maternal acute kidney injury (AKI) in critically ill obstetric patients. We found substantial regional heterogeneity in incidence rates, with the highest burden observed in African cohorts, while lower rates were reported in South-East Asia and high-income settings. Importantly, up to one in five women with maternal AKI required RRT (20.4%, 95% CI: 11.7–33.2). The requirement for renal replacement therapy identifies a subgroup of women with particularly severe disease and is consistently associated with higher reported mortality across studies. Despite a relatively high overall rate of renal recovery, the persistence of severe forms of AKI (KDIGO stage 2–3) and the variability in outcomes highlight the impact of disparities in healthcare resources, diagnostic criteria, and management strategies across regions.
Future studies should aim to standardize diagnostic definitions, improve early recognition, and optimize access to critical care and renal support therapies in resource-limited settings. Targeted interventions to prevent and manage the leading contributors—hypertensive disorders, haemorrhage, and sepsis—remain essential to reducing the global burden of maternal AKI and improving survival.
Taken together, our findings and prior literature converge on several key messages. First, maternal AKI remains a major global challenge, disproportionately affecting women in LMICs, where preventable causes such as preeclampsia, haemorrhage, and sepsis predominate, and access to dialysis is limited. Second, the need for RRT is a robust indicator of poor prognosis, and its association with mortality highlights the importance of timely recognition and intervention. Third, the variability in diagnostic definitions (KDIGO, RIFLE, AKIN, or clinical criteria) continues to hinder comparability across studies, reinforcing the call for standardized definitions and reporting in maternal critical care research. Finally, while renal recovery is achievable in most survivors, the burden of persistent dysfunction underscores the need for prevention, early diagnosis, and improved ICU capacity worldwide.
These findings should be interpreted in light of the substantial heterogeneity of the included studies, their predominantly observational design, and the restriction of the analysis to obstetric ICU populations.
Supplementary Material 1. Table S1. Search strategy by databaseSupplementary Material 2. Table S2. Risk of bias assessment of the included studies according to JBI criteriaSupplementary Material 3. Figure S1. Funnel plot of maternal AKI incidenceSupplementary Material 4. Figure S2. Leave-one-out sensitivity analysis of pooled maternal AKI incidence. Estimates were calculated on the transformed scale used for the primary meta-analysis and back-transformed to proportions for visualization. The red dashed line indicates the overall pooled estimate obtained from the full meta-analysis including all studies