Authors: Ji-Na Kim, Kyu Man Sim, Jung-Won Hwang, Sang-Hwan Do, Hyo-Seok Na
Categories: Research, Cesarean delivery, Hypotension, Multiple gestation, Lumbar wedge, Spinal anesthesia
Source: BMC Pregnancy and Childbirth
Authors: Ji-Na Kim, Kyu Man Sim, Jung-Won Hwang, Sang-Hwan Do, Hyo-Seok Na
Supine hypotension syndrome, caused by aortocaval compression of the gravid uterus in the supine position, is a common concern during cesarean delivery, particularly in women with multiple gestations. This retrospective study aimed to determine whether the use of a lumbar wedge reduces intraoperative hypotension in women with multiple gestations undergoing cesarean delivery under spinal anesthesia.
A total of 199 women with multiple gestations who underwent cesarean delivery under spinal anesthesia were included. Participants were divided into two groups based on lumbar wedge wedge (n = 108) and horizontal (n = 91). The primary outcome was the incidence of intraoperative hypotension, defined as the need for vasopressors (phenylephrine or ephedrine) at least once during surgery. Secondary outcomes included the total administered vasopressor dose and neonatal outcomes.
The incidence of intraoperative hypotension was significantly lower in the wedge group than in the horizontal group (70.4% vs. 86.8%; P = 0.005; RR, 0.8; 95% CI, 0.7 to 0.9). Phenylephrine requirements were significantly lower in the wedge group than in the horizontal group (4.0 ± 5.7 vs. 7.0 ± 7.7 µg/min; mean difference, -3.0; 95% CI, -4.9 to -1.1; P = 0.002), as were ephedrine requirements (0.04 ± 0.07 vs. 0.10 ± 0.13 mg/min; mean difference, -0.06; 95% CI, -0.09 to -0.03; P < 0.001). Neonatal cord blood gas values were within normal ranges, although some parameters differed significantly between groups. Specifically, the PCO2 levels of the first and third infants (P = 0.024 and 0.025, respectively), and the HCO3^−^ and base excess values of the second infant (P = 0.025 and 0.011, respectively), differed significantly between the wedge and horizontal groups.
The use of a lumbar wedge in patients with multiple gestations was associated with a significant reduction in the incidence of intraoperative hypotension during cesarean delivery under spinal anesthesia. These findings suggest that lumbar wedge positioning may be a simple, low-cost, and easily applicable technique to potentially enhance maternal hemodynamic stability and improve perioperative safety in multiple gestation pregnancies.
The online version contains supplementary material available at 10.1186/s12884-025-08540-w.
Supine hypotension syndrome is a clinically significant complication of pregnancy, particularly in women with multiple gestations. This condition results from the enlarged uterus compressing the inferior vena cava and partially compressing the aorta when the patient is in in the supine position [1, 2], leading to reduced venous return to the heart and subsequent hypotension. Twin pregnancy is a recognized risk factor for the supine hypotension syndrome [3, 4], because the uterus in such cases is larger, heavier, and has greater volume than in singleton pregnancies.
During cesarean delivery, the supine position is unavoidable and may cause aortocaval compression, especially in the third trimester. This physiological change produce symptoms ranging from mild discomfort to severe hypotension, or it may remain clinically silent due to compensatory collateral circulations, such as the azygos vein and vertebral venous plexus [2, 5]. A 15–30˚ left lateral tilt, typically achieved by placing a wedge under the right hip, is generally recommended to enhance venous return and reduce pressure on major vessels, thereby benefiting both the mother and the fetus [6–9]. Consequently, this maneuver is widely practiced to prevent supine hypotension syndrome in high-risk parturients [10, 11]. However, evidence indicates that uterine displacement using a lumbar wedge or lateral tilt offers limited clinical benefit in reducing maternal hypotension in singleton pregnancies [7, 9, 12], and no study has specifically assessed its effectiveness in women with multiple gestations. Given the larger uterus size and greater risk of aortocaval compression in twin or higher-order pregnancies, further studies are needed to evaluate the potential benefits of lumbar wedge or positional adjustments during cesarean section in this population.
This retrospective study aimed to compare the incidence and severity of hypotension during cesarean section under spinal anesthesia in pregnancies with multiple gestations, based on whether a lumbar wedge was used.
We conducted a retrospective study involving pregnant women with multiple gestations who underwent cesarean section under spinal anesthesia between January 2022 and October 2023. The study was approved by the Institutional Review Board of Seoul National University Bundang Hospital (IRB No. B-2402-884-103), and the requirement for informed consent was waived.
The inclusion criteria were multiple gestations, cesarean delivery under spinal anesthesia, and procedures performed by three obstetricians with more than five years of experience. The exclusion criteria included incomplete electronic medical records; the presence of gestational hypertension, preeclampsia, eclampsia, or cardiovascular disease; and conversion from spinal to general anesthesia during surgery.
Participants were divided into two groups based on the routine practice of attending obstetricians rather than individual patient those who had a lumbar wedge applied in the supine position (wedge group) and those who did not (horizontal group) (Fig. 1). In the wedge group, a lumbar wedge made of a medical gel pad measuring 10 \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ :\times:
\usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \:\times\: $$\end{document} 30 cm was positioned under the patient’s right lumbar area and remained in place until the completion of surgery. Fig. 1Schematic figure of positioning. F1, first fetus; F2, second fetus Data extracted from the electronic medical records (1) maternal baseline characteristics such as height, weight, body mass index, American Society of Anesthesiologists physical status classification, gestational type (singleton, twin, triplet), and placenta previa spectrum disorders; (2) fetal characteristics, including gestational age, and estimated fetal weight from prenatal ultrasound; (3) surgical and anesthetic characteristics such as administration of phenylephrine or ephedrine, total doses of these agents, preoperative epidural labor analgesia, magnesium sulfate administration before surgery, emergency surgery status, total surgery time (from initiation of anesthesia to completion of the procedure), pre-delivery period (from initiation of anesthesia to immediately before fetal delivery), post-delivery period (from immediately after fetal delivery to the end of surgery), baseline and intraoperative heart rate and systolic blood pressure measurements, doses of spinal anesthetics, and uterotonic agents administered post-delivery, excluding the standard 10 IU oxytocin infusion; and (4) neonatal characteristics, including Apgar scores at 1 and 5 min, neonatal height, birth weight, cord blood gas analysis, postpartum admission status, and the presence of a neonatologist at delivery. ### Study endpoints and outcome variables The primary outcome measure was the incidence of intraoperative hypotension. The incidence was first assessed separately for the periods before and after fetal delivery, followed by an evaluation of the overall incidence throughout the entire surgical procedure. The secondary outcomes included vasopressor doses during each period, adjusted for duration and expressed as doses per minute, as well as neonatal outcomes, such as APGAR score, cord arterial blood gas analysis, and NICU admission. Hypotension was defined based on the administration of antihypotensive agents rather than on blood pressure readings recorded in the electronic medical records. Blood pressure was monitored at 1-minute intervals, and antihypotensive agents were administered when systolic blood pressure fell below a predefined threshold. However, because only measurements at 5-minute intervals were automatically documented in the medical records, it was not possible to precisely identify hypotensive events using recorded blood pressure data alone. Spinal anesthesia was uniformly administered to all patients using conventional methods, and blood pressure was managed according to the institution’s standard obstetric anesthesia to ensure patient safety and hemodynamic stability. Phenylephrine was used as first-line therapy to maintain blood pressure when systolic blood pressure fell to ≤ 100 mmHg or decreased by more than 20% from baseline, accompanied by symptoms such as nausea, dizziness, tachycardia, or shortness of breath. If bradycardia (heart rate < 60/min) occurred concurrently with hypotension, ephedrine was administered. No prophylactic phenylephrine or ephedrine was administered. Therefore, in this retrospective study, hypotension was defined as the administration of vasopressors at least once while in the supine position. ### Statistics Data normality was assessed using the Shapiro–Wilk test. Continuous variables were analyzed using Student’s *t*-test or the Mann–Whitney U test, as appropriate, and are presented as the mean ± standard deviation (SD) with mean difference and 95% confidence interval (95% CI). Categorical variables were analyzed using the chi-square test or Fisher’s exact test and are presented as the number of patients (%) with risk ratio (RR) and 95% CI. A generalized linear mixed model (GLMM) with a binomial distribution and logit link function was used to compare the incidence of hypotension between groups after adjusting for covariates. In this model, the occurrence of hypotension was specified as the dependent variable, and relevant covariates (pre-delivery period, total surgery time, and group) were included as fixed effects. Patient-level variability was modeled as a random effect when appropriate. Odds ratios (OR) and corresponding 95% CI are presented for each fixed effect. All statistical analyses were performed using SPSS version 28.0 (IBM SPSS Statistics for Windows, Version 28.0; Armonk, NY, USA). Graphs were generated using SigmaPlot 10.0 (Systat Software, Inc., San Jose, CA, USA). A *P* value < 0.05 was considered statistically significant. ## Results A total of 893 pregnant women were identified from electronic medical records. After applying the exclusion criteria, 199 patients with multiple gestations were included in the final 108 in the wedge group and 91 in the horizontal group (Fig. 2). Maternal and fetal characteristics did not differ significantly between the two groups (Table 1).Fig. 2Flowchart depicting patient selection process Table 1Maternal and fetal baseline characteristicsVariableWedge (*n* = 108)Horizontal (*n* = 91)*P* valueMaternal baseline characteristics Height (cm)161.5 ± 6.0162.5 ± 4.80.249 Weight (kg)74.7 ± 11.776.3 ± 12.10.368 Pre-pregnancy weight (kg)58.5 ± 10.560.6 ± 110.184 Body mass index (kg/m^2^)28.6 ± 4.228.9 ± 4.30.678ASA Physical Status0.818 Ⅰ6 (5.8)7 (7.7) Ⅱ94 (88)78 (85.7) Ⅲ8 (7.4)6 (6.6)Multiple pregnancy0.877 Twin104 (96.3)88 (96.7) Triplet4 (3.7)3 (3.3)Placenta previa spectrum2 (1.9)2 (2.2)0.862Fetal baseline characteristics Gestational age (day)249.5 ± 36.1249.9 ± 16.00.922 Estimated fetal weight (g) First fetus2432.6 ± 395.92329.5 ± 468.00.108 Second fetus2381.1 ± 521.92325.7 ± 453.10.458 Third fetus1753.0 ± 267.31947.3 ± 283.50.275Data are presented as mean ± SD for continuous variables or number of patients (%)*ASA Physical Status* American Society of Anesthesiology Physical Status Anesthetic and surgical characteristics are summarized in Table 2. The duration of the pre-delivery period was significantly longer in the wedge group than in the horizontal group (mean difference, 5.9 min; 95% CI, 4.3 to 7.5; *P* < 0.001). Total surgical duration was also significantly longer in the wedge group compared with the horizontal group (mean difference, 22.5 min; 95% CI, 18.7 to 26.3; *P* < 0.001). Table 2Anesthetic & surgical characteristicsVariableWedge (*n* = 108)Horizontal (*n* = 91)*P* valueEmergency surgery18 (16.7)18 (19.8)0.570Preoperative ELA1 (0.9)1 (1.1)0.903Preoperative magnesium use14 (13.0)9 (9.9)0.499Systolic blood pressure (mmHg) Baseline132.0 ± 17.7131.6 ± 16.30.867 Pre-delivery period102.7 ± 10.9104.2 ± 10.20.321 Post-delivery period106.9 ± 11.8106.8 ± 15.20.959Heart rate (beats/min) Baseline86.2 ± 16.685.4 ± 15.50.727 Pre-delivery period79.6 ± 13.280.7 ± 14.80.580 Post-delivery period78.5 ± 13.075.8 ± 14.10.162Pre-delivery period (min)21.6 ± 6.515.7 ± 4.1< 0.001Total surgical duration (min)66.4 ± 14.543.9 ± 10.5< 0.001Doses of spinal anesthetics Heavy bupivacaine (mg)8.3 ± 0.78.3 ± 0.60.442 Fentanyl (µg)19.9 ± 0.819.9 ± 0.90.674Uterotonics Carbetocin33 (30.6)25 (27.5)0.634 Methylergonovine15 (13.9)13 (14.3)0.936 Sulprostone3 (2.8)1 (1.1)0.401Total colloid (ml)559.7 ± 152.5531.2 ± 119.50.172Total crystalloid (ml)843.9 ± 530.9841.6 ± 377.90.973Total urine output (ml/h)94.2 ± 88.282.1 ± 74.10.301Intraoperative pain sense12 (11.3)7 (7.7)0.414Data are presented as mean ± SD for continuous variables or number of patients (%)*ELA* Epidural labor analgesia ### The incidence of hypotension The incidence of maternal hypotension, as defined in this study, was lower in the wedge group than in the horizontal group for the total surgical period (70.4% vs. 86.8%; *P* = 0.005) (Fig. 3), with a RR of 0.8 (95% CI, 0.7 to 0.9). GLMM analysis indicated that total surgery duration did not have a statistically significant effect on the occurrence of hypotension (OR, 0.990; 95% CI, 0.961 to 1.019; *P* = 0.480). In contrast, the wedge group had significantly lower odds of hypotension than the horizontal group (OR, 0.662; 95% CI, 0.462 to 0.950; *P* = 0.025). Fig. 3Incidence of intraoperative hypotension during total surgical period and by pre- and post-delivery intervals. Error bars represent 95% confidence intervals calculated using the Clopper-Pearson exact method During the predelivery period, the incidence of hypotension was significantly lower in the Wedge group than in the Horizontal group (56.5% vs. 71.4%; *P* = 0.029) (Fig. 3) with a RR of 0.8 (95% CI, 0.6 to 0.9). GLMM analysis showed that group (Horizontal vs. Wedge) significantly influenced the occurrence of hypotension during the pre-delivery period (OR, 0.648; 95% CI, 0.452 to 0.927; *P* = 0.018), whereas the duration of the pre-delivery period itself did not (OR, 0.988; 95% CI, 0.960 to 1.018; *P* = 0.432). During the post-delivery period, the incidences of hypotension did not differ significantly between the two groups (60.2% vs. 72.5%; *P* = 0.067) (Fig. 3), with a RR of 0.8 (95% CI, 0.7–1.0.7.0). ### The requirement for medications to treat hypotension During the total surgical period, doses of vasopressors were significantly lower in the Wedge group for both phenylephrine (mean difference, − 0.0; 95% CI, −4.9 to −1.1; *P* = 0.002) and ephedrine (mean difference, −0.06; 95% CI, −0.09 to −0.03; *P* < 0.001) (Table 3). A significant difference was observed in the mean doses of phenylephrine administered during the pre-delivery period between the wedge and horizontal groups (mean difference, −3.0; 95% CI, −5.5 to −0.6; *P* = 0.012) (Table 3). However, the dose of ephedrine during the pre-delivery period was comparable between the two groups (mean difference, −0.02; 95% CI, −0.07 to 0.03; *P* = 0.489) (Table 3). During the post-delivery period, the Wedge group required significantly lower doses of both phenylephrine (mean difference, −3.0; 95% CI, −5.2 to −0.7; *P* = 0.007), and ephedrine (mean difference, −0.09; 95% CI, −0.13 to −0.05; *P* < 0.001) (Table 3). Table 3The use of medication for treating hypotension during the post-delivery and total anesthesia periodsVariableWedge(*n* = 108)Horizontal(*n* = 91)*P* value ***Total surgical duration*** Phenylephrine (µg/min)4.0 ± 5.77.0 ± 7.70.002 Ephedrine dose (mg/min)0.04 ± 0.070.10 ± 0.13< 0.001 ***Pre-delivery period*** Phenylephrine (µg/min)4.1 ± 7.07.2 ± 10.20.012 Ephedrine dose (mg/min)0.07 ± 0.140.08 ± 0.200.489 ***Post-delivery period*** Phenylephrine (µg/min)4.1 ± 6.97.1 ± 8.60.007 Ephedrine dose (mg/min)0.02 ± 0.090.11 ± 0.18< 0.001 ### Neonatal outcomes Neonatal outcomes are presented in Table 4. The height and weight of the second baby were significantly lower in the Horizontal group than in the wedge group. Cord blood pH values and PO~2~ levels were comparable across all groups (N1, N2, and N3) and remained within the normal range, indicating a stable acid-base balance. Significant differences in PCO~2~ were observed between groups N1 and N3 (*P* = 0.024 and *P* = 0.025, respectively), although all values remained within physiological limits. Statistically significant differences in HCO~3~^−^ and base excess were noted in group N2 (*P* = 0.025 and 0.011, respectively); however, these differences were unlikely to be clinically meaningful. Table 4Neonatal outcomesVariableWedge(*n* = 108)Horizontal(*n* = 91)*P* valueApgar 1 minN18.0 ± 1.58.2 ± 1.20.307N28.1 ± 1.28.0 ± 1.40.588N36.0 ± 1.46.0 ± 1.41.000Apgar 5 minN19.2 ± 1.39.4 ± 0.90.217N29.4 ± 0.99.3 ± 1.00.459N38.5 ± 0.78.5 ± 0.71.000Height (cm)N146.6 ± 2.746.4 ± 3.50.650N246.6 ± 2.845.7 ± 3.40.042N343.5 ± 3.544.5 ± 0.90.656Birth weight (g)N12493.5 ± 426.52358.7 ± 543.90.052N22395.3 ± 393.22244.3 ± 543.50.024N31780.0 ± 551.51866.7 ± 92.90.803Cord arterial blood gas analysis*pHN17.3 ± 0.07.3 ± 0.01.000N27.3 ± 0.07.3 ± 0.01.000N37.3 ± 0.07.3 ± 0.01.000PCO~2~ (mmHg)N147.2 ± 6.144.8 ± 6.60.024N246.9 ± 4.946.2 ± 8.10.514N349.4 ± 1.741.1 ± 5.00.025PO~2~ (mmHg)N130.2 ± 6.528.5 ± 8.40.168N227.7 ± 6.427.7 ± 11.11.000N331.3 ± 2.630.2 ± 4.90.713HCO~3~^−^ (mmol/l)N124.0 ± 1.923.5 ± 2.60.179N224.4 ± 1.723.6 ± 2.60.025N323.2 ± 1.822.4 ± 2.40.633Base excess (mmol/l)N1−2.0 ± 1.3−2.2 ± 1.90.448N2−1.5 ± 1.3−2.2 ± 2.00.011N3−3.5 ± 2.1−2.7 ± 1.70.614Postpartum admission,NB/NICUN182/26 (75.9/24.1)69/22 (75.8/24.2)0.987N279/29 (73.1/26.9)64/27 (70.3/29.7)0.660N32/2 (1.9/1.9)0/3 (0/3.3)NANeonatologist attendance,on standby/called duringdelivery/not requiredN121/14/73 (19.4/13.0/67.6)16/12/63 (17.6/13.2/69.2)0.945N220/14/74 (18.5/13.0/68.5)20/16/55 (22.0/17.6/60.4)0.475N34/0/0(100/0/0)3/0/0(100/0/0)NAData are presented as mean ± SD for continuous variables or number of patients (%)*N1* first-born baby, *N2* second-born baby, *N3* third-born baby, *NB* newborn room, *NICU* neonatal intensive care unit, *NA* not availableThe outcome for N3 was calculated based on 4 and 3 cases in the Wedge and Horizontal groups, respectively* Cord arterial blood gas analysis was omitted for uncomplicated deliveries without risk factors or when cord blood volume was insufficient. N1 and N2 were analyzed in 87 cases in the wedge group, 61 cases in the horizontal group, and N3 in four and three cases, respectively ## Discussion In this study, we found that applying a lumbar wedge during cesarean delivery under spinal anesthesia reduced the incidence and severity of intraoperative hypotension, as indicated by the lower vasopressor requirements in patients with multiple gestations. Specifically, the use of the lumbar wedge resulted in a 16.4% absolute risk reduction in maternal hypotension compared with the horizontal position. To the best of our knowledge, this is the first study to evaluate the effect of lumbar wedge use on intraoperative hypotension in this population. Supine hypotension syndrome typically develops when aortocaval compression is pronounced or compensatory mechanisms are insufficient, affecting up to 8% of patients and increasing to 15% at full term [1, 13, 14]. To prevent this condition, a left lateral tilt with a wedge is recommended, although it has minimal effect on reducing hypotension in singleton pregnancies [7, 9, 12]. Consistent with previous findings, our supplementary analysis of singleton gestations showed no significant difference in the incidence of intraoperative hypotension (Table S1). In contrast, twin pregnancy has been identified as a risk factor for increased vasopressor requirements, with one study reporting a 1.38-fold higher prophylactic ephedrine dose in twin pregnancies than in singleton pregnancies [15]. Additionally, Umazume et al. [16] reported that the diameter of the inferior vena cava in the supine position was significantly smaller in multiple gestations compared with singleton pregnancies, as shown by echocardiography. In our study, the incidence of intraoperative hypotension, as indicated by a lower vasopressor requirement, was lower in the wedge group. These findings suggest that, unlike in singleton gestations, the use of a lumbar wedge in multiple gestations may help alleviate supine hypotension syndrome to some extent. When a lumbar wedge was used, not only was the incidence of hypotension lower, but the requirement for therapeutic agents to treat it was also reduced, indicating a difference in the severity of hypotension. In this study, hypotension was analyzed separately for the periods before and after fetal delivery. This distinction was important because aortocaval compression is relieved after delivery, whereas the post-delivery period is more vulnerable to confounding factors, such as administration of uterotonic agents or postpartum hemorrhage. In addition, the wedge group had a longer surgical duration, which may have reflected unmeasured procedural or patient-related factors. To minimize these influences, hypotension was evaluated within the pre- and post-delivery intervals, and vasopressor requirements were standardized according to surgical duration. Although the wedge group demonstrated a lower incidence of hypotension and vasopressor requirement after adjusting for surgery duration, the potential influence of unmeasured confounders related to surgical conditions or patient characteristics cannot be excluded. Although no difference in the incidence of hypotension was observed after delivery, the consistently lower requirements for both phenylephrine and ephedrine in the wedge group suggest that wedge placement may have attenuated the overall severity of hypotension, as reflected by the reduced need for therapeutic agents. Furthermore, delayed normalization of the inferior vena cava diameter after delivery has been reported in patients with twin pregnancies compared with those with singleton pregnancies [16], which may have been partially mitigated by the use of a lumbar wedge. The lower frequency of hypotension throughout the surgical period in the wedge group appears to reflect the cumulative hemodynamic benefits achieved during the pre-delivery period. However, it must be acknowledged that confounding surgical factors after delivery may not have been fully controlled, and further investigation is needed to clarify this issue. Patients with spinal-induced hypotension could not be completely excluded from this cohort. Although the incidence of hypotension was lower in the lumbar wedge group than in the horizontal group, it remained high in both groups (70.4% and 86.8%, respectively). International consensus guidelines recommend prophylactic vasopressor administration in conjunction with fluid loading during spinal anesthesia for cesarean delivery [17–20]. Despite the potential benefits of the lumbar wedge in reducing hypotension, its preventive effect could not be determined exclusively in this study due to the absence of standardized prophylactic management across patients. However, because interventions other than lumbar wedge positioning were administered consistently, it is unlikely that spinal-induced hypotension confounded the comparison between the two groups. Further research is warranted to evaluate the efficacy of lumbar wedge positioning in multiple pregnancies, particularly when combined with recommended prophylactic strategies, such as vasopressor infusions and fluid optimization. Cord blood gas analysis revealed differences in a few parameters (PCO~2~, HCO~3~^−^, and base excess), whereas pH and PO~2~ remained stable. No significant differences were found between groups in Apgar scores, NICU admissions, or neonatologist attendance. The results may reflect the short duration of hypotension and its prompt detection and management [21, 22]. Although these findings suggest minor statistical differences, they appear to lack clinical relevance. Given the limited power for analyses due to insufficient sample size, the findings should be interpreted with caution. However, as prolonged hypotension has been associated with neonatal acidosis [23], continued efforts to minimize the frequency and severity of hypotensive episodes in multiple pregnancies remain warranted. As this was a retrospective study, several inherent limitations must be acknowledged. First, hypotension was defined by vasopressor administration rather than by objective blood pressure recordings; therefore, its severity could only be inferred from vasopressor requirements. Although direct confirmation of hypotension using accurate blood pressure measurements would have been ideal, the retrospective design precluded such analysis. Second, lumbar wedge placement was provider dependent and not strictly protocolized, which may have introduced variability in the extent of aortocaval compression relief. Previous studies have reported that a systolic arterial pressure difference of 20–25 mmHg between the upper and lower limbs may indicate significant aortocaval compression [24]. However, such measurements were not systematically obtained in this study, limiting the precision of aortocaval compression assessment, particularly in high-risk populations such as women with multiple gestations. Given the importance of accurate assessment, future research should incorporate quantitative methods, such as upper- to lower-limb arterial pressure gradients. Third, group allocation was based on each obstetrician’s routine practice rather than randomization. Although this approach avoided case-by-case preference, it introduced the potential for selection bias, as unmeasured institutional or provider-related factors may have differed systematically between groups. These issues warrant cautious interpretation of the results and underscore the need for further randomized studies with detailed adjustment for perioperative factors. Finally, this study was a retrospective analysis and may have been subject to selection bias and missing data inherent to such designs. To mitigate these biases, objective inclusion and exclusion criteria were applied, and data extraction from electronic medical records was conducted by a single experienced researcher to ensure consistency. Missing data, particularly regarding neonatal outcomes, were transparently reported. Nevertheless, these limitations may affect the generalizability of fetal outcome findings and introduce potential bias due to incomplete data capture. Additionally, because the study was conducted at a single center, findings may not fully represent diverse patient populations, thereby limiting external validity. Future prospective multicenter studies are warranted to confirm and expand these results. ## Conclusion The use of a lumbar wedge in patients with multiple gestations was associated with a significant reduction in the incidence of intraoperative hypotension during cesarean delivery under spinal anesthesia. These findings suggest that lumbar wedge positioning may be a simple, low-cost, and easily applicable technique that obstetric anesthesiologists can consider incorporating into routine practice to potentially enhance maternal hemodynamic stability and improve perioperative safety in multiple gestation pregnancies. However, due to the observational nature of the study, causality cannot be established. Further large-scale, randomized controlled trials are needed to confirm these associations and to optimize preventive strategies tailored for multiple gestation pregnancies. ## Supplementary Information Supplementary Material 1.