Maternal mortality and morbidity remain challenging issues in developing countries. In recent years, the incidence of scarred uterus and complications in late pregnancy has increased significantly with the implementation of two-child and three-child policy in China^{[1, 2, 3]}. Profound physiologic changes affecting the cardiovascular, endocrine, urinary and respiratory systems during pregnancy can predispose women to serious obstetric complications, Furthermore,the need to fetal well-being adds a layer of complexity, making the managemen of critically pregnant women is a significant challenge for ICU clinicians ^{[4, 5]}.Maternal admission to ICU during pregnancy or postpartum is a marker of severe acute maternal morbidity (SAMM)^{[6, 7, 8]}. Critically pregnant women admitted to the ICU often require invasive hemodynamic monitoring, Mechanical ventilation (MV) and blood purification^{[9, 10]}. The implementation of these measures is associated with prolonged hospital stay, increased cost and poor prognosis.

MV is an important measure of advanced life support, not only provide respiratory support in surgical patients, but also afford active life support in patients with inadequate ventilation. Studies had shown that prolonged mechanical ventilation (PMV) is associated with complications and increased medical cost^[11], PMV in critically ill pregnant women has also received increasing attention in recent years. Similar studies have been conducted globally, but the data on MV is relatively less. We conducted a retrospective study, The primary outcome was the risk factors for PMV in critically pregnant women. Secondary outcomes was the the predictive ability of the multivariate regression model.

This retrospective observational study was conducted in the Third Affiliated Hospital of Guangzhou Medical University (GAMU),a major obstetric critical care center in South China (Guangzhou,Guangdong), We screened the medical records of all pregnant and postpartum women admitted to the ICU between January 1, 2019 and April 30, 2025. The inclusion criteria were: 1. Pregnant or postpartum women. 2. those who requiried invasive mechanical ventilation during their ICU stay. Patients were excluded if they were: 1. under 18 years of age; 2. discharged from the hospital while still requiring mechanical ventilation. All patients signed a clinical research informed consent form before treatment, and the study was approved by the Ethics Committee of the Third Affiliated Hospital of Guangzhou Medical University: [2024]No. 167.

༟༟A total of 621 patients were included in the final analysis. During the six-year study period (2019–2025), 1182 critically ill pregnant women were admitted to the ICU, accounting for approximately 2%(1182/66746)of all obstetric admissions to our hospital. Of these ICU admissions, 621 patients required mechanically ventilation and met the study criteria (Fig. 1).

The primary etiologies leading to MV are detailed in Table 2, The five most frequent causes were hypertensive disorders of pregnancy (18%, 110/621), postpartum hemorrhage (18%, 109/621), hepatic (13%, 78/621), cardiac disease (12%, 74/621), and respiratory failure (10%, 63/621), Collectively, these conditions accounted for 70% (434/621). Based on whether the duration of MV was > 24 hours, we divided the patients into two groups: 354 (57%) cases in the ≤ 24 hours group and 267 (43%) cases in the > 24 hours group. BMI, mortality, APACHE II score, volume of red blood cell transfusion, volume of plasma transfusion, staging of renal injury, myocardial injury, and oxygenation index were significantly different between the two groups ( p < 0.05). More patients were referred from external hospitals (76%). The referred proportion from external hospitals in the group with ≤ 24 hours of MV was 71%, which was significantly lower than in the group with > 24 hours (84%)(p < 0.05), indicating that patients transferred from external hospitals were significantly more serious. The overall APACHE II score median was 17, which was 19 in the group with a duration of MV > 24 hours, and 15 in the ≤ 24 hours group (Table 3).

More than half (52%,326/621) of the patients developed AKI. The proportion of AKI was significantly higher in the group with ≥ 24 hours of MV (67% vs 42%, p < 0.05). Univariate analysis showed that volume of red blood cell transfusion, volume of plasma transfusion, multiple (≥ 2) surgeries, APACHE II score, AKI grading, myocardial injury, B-type Natriuretic Peptide(BNP), Procalcitonin (PCT), and volume of fluids discharged were the risk factors for the duration of MV ( p < 0.05) (Table 4).

Multivariable logistic regression analysis identified three independent risk factors for prolonged MV (> 24 hours):volume of RBC transfusion (OR = 2.66, 95% CI: 1.77–3.56; P < 0.001), volume of plasma transfusion (OR = 7.83, 95% CI: 4.19–11.46; P < 0.001) and AKI grading (OR = 13.17, 95% CI: 3.64–22.69; P = 0.007) were (Table 4). The area under the ROC curve of the prediction model based on independent risk factors was 0.708(95% CI: 0.665–0.750) (Fig. 2).

In this retrospective study of critically ill pregnant women, we identified several factors associated with a prolonged duration of mechanical ventilation, Univariate analysis revealed associations with transfusion volumes, multiple (≥ 2) surgeries, APACHE II score, number of hours of hemofiltration, AKI grading, myocardial injury, elevated BNP and PCT levels, and fluids balance. However, multivariable analysis demonstrated that the volumes of RBC and plasma transfusion, along with the AKI grading, were independent risk factors for prolonged MV.

Maternal critical illness is often acute and severe, with high risk of multiple organ dysfunction syndromes (MODS)^[12]. ICU care can improve survival^{[9, 13]}, yet prolonged mechanical ventilation (PMV) prolongs hospitalization and resource use. Definitions of PMV range widely^[14–18]; we adopted the Society of Thoracic Surgeons (MV > 24 hours), as it reflects clinically meaningful deterioration and is widely applied for risk stratification. In our study, transfusion volume, multiple surgeries, APACHE II score, hemofiltration, AKI grade, myocardial injury, BNP, PCT, and fluid balance were significant predictors (p < 0.05).

In our study, the incidence of critically ill pregnant women admitted to the ICU and requiring MV was 53%(621/1182), 267 (43%) of whom were ventilated for more than 24 hours, which is similar to the results of a Chinese multicenter report^[13]. However, it has also been reported^[9] that among 360 critically ill pregnant women admitted to an ICU, only 25 were mechanically ventilated for ≥ 24 h (6.94%). The reason for the obviously difference in the analysis was the different severity of the patients admitted, the median APACHE II score for critically ill pregnant women in that study was 7, which is far from the median APACHE II score of 19 in our study.

This study identified red blood cell transfusion, plasma volume, and AKI as independent predictors of PMV. Fluid resuscitation with excessive input and reduced renal output may precipitate fluid overload, pulmonary edema, and impaired lung function, thereby extending ventilatory dependence^[19]. Although the oxygenation index (OI) is widely recognized as a marker of lung injury and an important risk factor for PMV^{[9, 20, 21]}, our findings did not confirm this association. A likely explanation is that 76% of patients were referred from other hospitals, many of whom had received oxygen therapy or mechanical ventilation prior to transfer, leading to improved OI values upon admission. Nonetheless, OI still differed significantly between patients ventilated ≤ 24 h and those ventilated > 24 h.

Pregnancy-related hypertensive disorders and postpartum hemorrhage were the leading causes of ICU admission in our cohort, each accounting for 18% of mechanically ventilated cases (110/621 and 109/621, respectively), in line with previous reports^{[9, 22–23]}. Both conditions are well-recognized contributors to AKI in obstetric populations^[24], and patients with pregnancy-related AKI often require mechanical ventilation and renal replacement therapy, with generally poor outcomes^[25]. Consistent with our findings, renal dysfunction may exacerbate fluid overload, aggravate pulmonary injury, and thereby prolong ventilatory dependence. National data further indicate that hypertensive disorders of pregnancy account for 27.3–46.1% of obstetric ICU admissions in China, higher than the 22.3–29.9% reported internationally ^[9]. The rising incidence of postpartum hemorrhage in China may be partially attributable to the two- and three-child policies, which have increased the prevalence of cesarean scar uterus and late-pregnancy complications^{[1, 2]}. Pathophysiologically, severe hypertensive disorders may lead to microangiopathic hemolysis, hepatic dysfunction, cardiac insufficiency, and renal impairment^[26], while postpartum hemorrhage is commonly associated with uterine atony, birth canal trauma, placental abnormalities, and coagulation disorders^[27].

Our findings indicate that myocardial injury and elevated BNP are important predictors of PMV in critically ill obstetric patients. Cardiovascular impairment in this population is often driven by hypertensive disorders of pregnancy and postpartum hemorrhage, which exacerbate hypoperfusion, hypoxia, and fluid overload. Prior studies have reported similar associations, including myocardial injury in over half of patients with severe postpartum hemorrhage^[28] and frequent troponin elevation in women with hypertensive disorders of pregnancy^[29]. Together, these results emphasize the central role of cardiac dysfunction in prolonging ventilatory support.

We also observed a strong association between elevated PCT and PMV, underscoring the impact of infection and systemic inflammation. Maternal sepsis is a leading cause of ICU admission and is often complicated by multiorgan failure and high mortality^[30–32], yet nearly half of sepsis-related deaths are considered preventable with early recognition and intervention^[33]. Monitoring PCT may therefore provide clinical value in identifying infection-related deterioration, predicting PMV, and guiding timely management in this high-risk population.

There are some limitations to this study. First, this study was a single-center study, the admission criteria may differ from other studies; Second, the data were analyzed retrospectively, and some data from patients' external hospitals were missed, which may led to data bias. Third, we derived three independent risk factors for prolonged MV and created a mapping diagram for visualizing and promoting clinical practice. However, we did not validate the nomogram with a new database. a prospective study is needed to address these issues and validate our findings.

Therefore, we propose the following recommendations: 1)early identification and assessment of critical pregnancies; 2) attention to and timely control of obstetric hemorrhage; 3) during fluid resuscitation, in addition to actively maintaining hemodynamic stability and tissue perfusion, it is necessary to prevent excessive fluid intake; 4) close monitoring of the function of the kidneys, lungs, heart, and other organs of the critically ill mother; 5) focus on infections, critical pregnant women who develop infections or are at risk of infection need to be assessed early and managed appropriately, e.g., timely specimen retention and antibiotic use. In conclusion, the early assessment and management of critically ill pregnant women admitted to the ICU is very important and even requires the participation of multiple specialists such as obstetricians, respiratory and cardiovascular physicians in addition to ICU physicians in the management of critically ill obstetrics patients in order to shorten the duration of mechanical ventilation.