Abstract 
Background:  The postpartum period, which includes the 12 weeks after delivery, is considered the fourth trimester. During this period, postpartum complications such as febrile morbidities, thromboembolic events, preeclampsia, etc. can lead to readmission and morbidity in mothers. Therefore, this study investigated the prevalence of post-partum patient readmission in university hospitals of Ahvaz, southwest of Iran during 2020-22.
Methods: This retrospective cross-sectional descriptive study was conducted in university hospitals affiliated to Ahvaz Jundishapur University of Medical Sciences during 2020-22. All pregnant mothers who were re-admitted to hospital during their postpartum period were examined.
Results: Between 2020 and 2022, a total of 21,498 births took place in Ahvaz University Hospitals. Of these, 8,071 were Vaginal Deliveries (VDs) and 13,427 were Cesarean Section (CS). The prevalence of readmission was 1.39%. The most common cause of readmission was febrile complications, with pelvic abscess (17.7%) and metritis (27%) being the most frequent. Pelvic abscess occurred only in women with cesarean delivery. Wound dehiscence rates were 3.3% for episiotomy and 4.7% for cesarean. Blood transfusion was required in 35.5% of cases, with 7.0% related to VD and 26.5% to CS.
Conclusion: This study showed that in patients undergoing CS, there were greater rates of postpartum readmission and morbidity and longer length of hospital stay. The most common cause of hospitalization was febrile morbidity followed by delayed postpartum hemorrhage, Abscess, Episiotomy,  Hospitals, University, Iran
Keywords: Cesarean Section, Length of Stay, Patient Readmission, Postpartum Hemorrhage, Pre-Eclampsia, Prevalence, Retrospective

 Introduction
Post-partum readmission is considered a key indicator in evaluating the quality of healthcare services. Such readmissions can highlight existing medical issues and deficiencies in post-partum care, thereby holding significant importance. Various factors, including infections, surgical complications, psychological problems, and inadequate follow-up care, can lead to the readmission of patients after childbirth. The primary objective of this research is to determine the rate of post-partum readmission in university hospitals of Ahvaz and to identify the factors influencing it. The secondary objectives include examining the impact of demographic and clinical variables on the prevalence of readmission. A precise understanding of these factors can contribute to improving the quality of post-partum care and reducing health issues among mothers. Results of this study can assist policymakers and healthcare managers in enhancing care processes and elevating the quality of services provided to mothers after childbirth. 
The word postpartum is derived from Latin-puer, child+parus, bringing forth. It defines the time following delivery during which pregnancy-induced maternal anatomical and physiological changes return to the nonpregnant state. Its duration is inexact but is considered to last between 4 and 6 weeks (1). The postpartum period is a critical time when pregnancy-related and chronic diseases can dramatically affect the mother’s health (2). Most deaths related to pregnancy occur after delivery, and recently there has been an increase in maternal complications. Previous studies have identified the factors leading to prolonged hospital stay or readmission. These include maternal age (3), comorbidities (4), multiple births (5), and cesarean delivery (6,7). Although several studies have identified what factors influence postpartum readmission, most focused on the relationship between postpartum readmission and mode of delivery, with Cesarean Section (CS) being particularly associated with postpartum readmission (8). In obstetrics and gynecology, post-partum readmission occurs almost in 1 out of every 50 births, with the most common cause of readmission being infection (15.5%), followed by high blood pressure (9.3%), and mental illnesses (7.7%). Some of these were of an unexpected origin, and many could have been prevented (8). Postpartum Hemorrhage (PPH) remains a leading cause of maternal morbidity and mortality worldwide. While the overall prevalence is estimated to be between 2% and 4%, the risk is significantly higher following CS, with rates reported between 2% and 6% (9). Uterine atony accounts for more than 50% of PPH cases, followed by residual tissue, wound dehiscence, coagulation problems, and uterine rupture (10). PPH has long-term and short-term effects such as chronic disease, disability, increased risk of death and/or poor growth and development of children, liver dysfunction, adult respiratory distress syndrome, and kidney failure (11-13). PPH occurs approximately at a rate of 8.7 million cases per year and causes 44,000 to 86,000 annual deaths, making it the leading cause of death during pregnancy worldwide (14). In developing countries, postpartum hemorrhage (PPH) is the primary cause of maternal death, accounting for 25 to 43% of all maternal mortality cases. In contrast, developed countries primarily experience maternal mortality due to pulmonary embolism (9). On the other hand, maternal morbidity and mortality is a global socioeconomic and health care burden, and infections are relatively common and preventable in the postpartum period, with 5 to 7 percent of women being affected during this period. Puerperal sepsis is one of the five leading causes of maternal mortality worldwide, accounting for 10-15% of all deaths in the postpartum period. Infections are also the most common cause of death following spontaneous or induced abortions (15). Other postpartum problems and complications include postpartum depression, sleep deprivation, and breastfeeding problems, although they rarely account for readmission (16). Despite the importance of postpartum hospitalization, few population-based studies have examined this topic (17). Postpartum care is an important part of maternal care, since life-threatening complications can occur in the postpartum period (18). On the other hand, compared to the ratio of maternal mortality, severe maternal morbidity is a useful indicator for evaluating and improving maternal health services (19). While postpartum readmission is commonly used as an indicator of postpartum maternal complications (20), its potential as a quality indicator in obstetrics and gynecology care has been less explored (21,22). Therefore, this study investigated the prevalence of postpartum readmission in Imam Khomeini and Taleghani hospitals in Ahvaz during 2020-2022.

Materials and Methods 
This study was registered with the Ethics Committee of Ahvaz Jundishapur University of Medical Sciences under the code IR.AJUMS.HGOLESTAN.REC.1401.103.
This cross-sectional observational epidemiological study investigated the prevalence of postpartum readmissions of women in teaching hospitals in Ahvaz from 2020 to 2022. The selection of participants was based on all cases of postpartum readmission at Imam Khomeini and Taleghani hospitals during the study period from April 2020 to March 2022. The source population consisted of 21,489 women who gave birth in these hospitals, of which 300 were readmitted within the first six weeks postpartum. After excluding 85 cases due to incomplete data or inaccessible records, 215 patient records were included in the final analysis. Inclusion criteria encompassed all pregnant women (both singleton and multiple pregnancies) who delivered at these centers. Exclusion criteria included incomplete or inaccessible medical records or cases where the patients did not deliver at these centers.
For each eligible patient, the following information was collected and analyzed: type of delivery (vaginal or cesarean section), age, parity, underlying conditions (such as diabetes, hypo/thyroidism, asthma), cause of readmission (e.g., postpartum hemorrhage, metritis, pelvic abscess, embolism, preeclampsia, hypertensive crisis, urinary complications, episiotomy dehiscence, cesarean wound dehiscence), need for ICU admission, need for blood transfusion, and discharge status. The study used SPSS software version 26 (IBM Corp., Armonk, NY, USA) for data analysis. Descriptive statistics, including frequency and percentage, were used for categorical variables. The chi-square test was applied to assess differences between qualitative variables. A p-value of less than 0.05 was considered statistically significant.
This study adhered strictly to ethical principles outlined in the Declaration of Helsinki. All the patients’ information was anonymized and kept confidential, and the data were used solely for research purposes. The Declaration of Helsinki, first adopted by the World Medical Association in 1964 and most recently amended in 2008, provides ethical guidelines for medical research involving human subjects. This ensures that the rights and welfare of participants are protected.
In terms of statistical analysis, the significance level was set at p<0.05. Although hypothesis testing using p-values was applied, additional attention was paid to the representation of effect sizes where appropriate. The statistical design and methodology were selected following standard works in epidemiology, and all the statistical terms, abbreviations, and symbols were clearly defined to facilitate the interpretation of results by knowledgeable readers.

Results
Between April 2020 and March 2022, 21,489 women delivered at Ahvaz University Hospitals (Imam Khomeini and Taleghani). Of these, 300 were readmitted within six weeks postpartum. The overall readmission rate was 1.39% (higher for cesarean section: 1.21% vs. vaginal delivery: 0.61%) (Table 1). Due to incomplete data and unavailability of some records owing to administrative restrictions in the hospital archives and statistics departments, 85 records were excluded, leaving 215 patient records for review. In this cohort, 75.81% of the patients were readmitted after CS, 23.2% after Vaginal Deliveries (VD), and 0.93% after cesarean hysterectomy (due to placenta accreta syndrome and uterine atony). The majority of the patients (65.6%) were in the age range of 21-35 years. More than half of the women (55.3%) in this study were multiparous, and 44.7% were nulliparous. The most common comorbidity among the patients was diabetes mellitus (10.7%), followed by hypothyroidism (6.5%) and asthma (2.3%) (Table 2).
The most common causes of readmission included febrile morbidity (comprising metritis and pelvic abscess) and postpartum hemorrhage. Febrile morbidity affected 44.7% of the patients. Metritis was observed in 27% of the patients, with a significantly higher incidence in the cesarean section group (15.8 vs. 10.7% in vaginal delivery; p=0.001). Pelvic abscess was reported in 17.7% of the cesarean cases and was not observed in the vaginal deliveries (p<0.001). Postpartum hemorrhage occurred in 44.2% of the patients, with 11.6% following vaginal delivery and 32.6% following cesarean section (p=0.26). Other causes included episiotomy dehiscence in 3.3% of the vaginal delivery patients (p<0.001), cesarean wound dehiscence in 4.2% of the cesarean section cases (p=0.23), and postpartum urinary complications in 3.7% of the cesarean section patients (p=0.27). There were no statistically significant differences between the groups in terms of the occurrence of embolism (0.9% of patients, p=0.65), preeclampsia (1.9% of cesarean cases, p=0.53), or hypertensive crisis during pregnancy (1.39% of cesarean cases, p=0.51). Emergency hysterectomy was required in 0.9% of the cesarean section cases (p=0.69) while elective hysterectomy was performed in 2.3% of the cesarean cases. ICU admission occurred in 13% of the patients, with 5.1% following vaginal delivery and 7.9% following cesarean section (p=0.05). Blood transfusion was administered to 33.5% of the patients, with 7.0% related to vaginal delivery and 26.5% to cesarean section (p=0.50). At discharge, 78.1% of the patients were discharged with medical approval and 21.9% discharged upon personal consent. The length of hospital stay was 1-3 days in 54.9% of the patients, 3-14 days in 42.8%, 14-21 days in 0.9%, and more than 21 days in 1.4% of the patients (p=0.70) (Table 3).
Additionally, chi-Square test results indicated that postpartum hemorrhage (p=0.006), metritis (p=0.002), and pelvic abscess (p< 0.001) were significantly more prevalent in the age range of 21-35 years (Table 4). 

Table 1. Prevalence of readmission

*Out of the 300 patients who were readmitted, only 215 were examined and included in the study.

Table 2. Demographic and clinical characteristics of the patients

Table 3. Cause of readmission and postpartum complications (from 215 cases)

**Chi-Square Test

Table 4. Distribution of postpartum complications by age group

**Chi-Square Test

Discussion
Results of this study showed that the overall prevalence of readmission in the studied teaching hospitals in Ahvaz during 2020-22 was 1.39 cases, of which 76.74% were related to CSs and 23.25% to VDs. Of all the studied patients, two had hysterectomy during CS: one due to accreta syndrome, and the other due to atony during labor. The most common cause of readmission in this study was puerperal infections (44.47%), bleeding (44.42%), afebrile wound complications (7.5%), pre-eclampsia (1.9%), blood pressure crisis (1.39%), and embolism 0.93%. Patients undergoing CS were readmitted about 3 times more than patients with VD. Moreover, bleeding complications leading to hysterectomy, embolism and pelvic abscess were observed only in patients having CS. Finally, 7 patients (3.3%) underwent hysterectomy, and all were among those having cesarean delivery. 
In Matas et al’s study in 2017, the prevalence of readmission was 1.4-9.4, which is consistent with our results (23). Fein et al investigated the risk factors of bleeding leading to postpartum readmission, and the prevalence of bleeding and readmission was reported to be 6.06%, with 14.28% of the cases undergoing CS (24). In the current study, 44.2% of the patients were admitted with bleeding, of whom 26.5% received pack cell, which could explain why the rate obtained in this study was higher than that in Finn et al’s. In La Rosa et al’s study, the most common causes of postpartum readmission were febrile complications and high blood pressure (25). In the present study, the most common cause was febrile morbidities and bleeding, which were more common in CS cases, and a small percentage of patients were hospitalized due to high blood pressure (44.6 vs. 1.39), which is not consistent with La Rosa et al. In 2016, Clapp et al reported the prevalence of readmission to be 1.72-2.16%, with the most common causes being infections, high blood pressure, and psychiatric diseases (21). These results are not in line with ours where the readmission prevalence was 1.39% and the most common cause was metritis followed by bleeding. The prevalence of readmission in Clapp et al’s study in 2017 in Boston (26), Hamilton et al’s study in 2023 in Maryland (27) and Liu et al’s study in 2005 in Canada (28), was 1.34, 1.5 and 1.3%, respectively, which is consistent with the current study (1.39%). In Liu et al’s study, the most frequent causes of readmission were febrile complications including metritis and pelvic abscess, followed by thromboembolism (28), which was consistent with this study in terms of the prevalence of metritis, but not in terms of the prevalence of thromboembolism. Based on the results obtained, it can be concluded that despite the increase in the prevalence of CS over the past years, the prevalence of readmission has not increased. However, readmission among CS patients is of paramount importance since complications such as pelvic abscess, thromboembolism, and bleeding complications leading to hysterectomy were only observed in this group of patients.
According to the results, postpartum hemorrhage, metritis, and pelvic abscess were significantly more prevalent in the age range of 21 to 35 years. Axelsson et al demonstrated that advancing age and higher Body Mass Index (BMI) are associated with an increased prevalence of postpartum infections. Their study, which included women aged 15 to 50 years, reported that both advanced age and elevated BMI correlate with heightened risks of surgical site infections, urinary tract infections, and metritis (29).
Aviram et al found that younger mothers (≤21 years) are at a greater risk of short-term postpartum complications such as postpartum hemorrhage and lower neonatal Apgar scores, when compared to older age groups (22-25, 26-30, 31-35, and 36-40 years) (30). Furthermore, Watts et al reported that women under 25 years with bacterial vaginosis are at increased risk for postpartum endometritis  (31). A study conducted by Shmueli et al in 2019 indicated that women older than 30 years with endometriosis are more likely to undergo cesarean delivery and experience postpartum hemorrhage (32).
Several factors might contribute to these findings. Firstly, heightened hormonal activity in younger women could potentially increase the risk of infections and postpartum complications (33). Additionally, vaginal delivery, which is more prevalent in younger women, is associated with a higher risk of infections and hemorrhage. A previous study noted that vaginal delivery could be a factor in rehospitalization due to postpartum metritis (34). Other common risk factors such as a history of infections or similar medical conditions also play a significant role (35). Moreover, multiple pregnancies and deliveries in this age group may further elevate the risk of postpartum complications (36). Therefore, a combination of physiological factors, type of delivery, and medical history can elucidate why women in this age group are more susceptible to rehospitalization due to hemorrhage and febrile morbidity (comprising metritis and pelvic abscess).
In this study, the length of hospital stay in the CS group was longer than that in the VD group. Overall, postpartum complications in CS patients were more common compared with those having vaginal delivery. Since postpartum metritis and bleeding were the most common causes of readmission after vaginal and caesarean delivery in the present study, future studies are recommended to focus more carefully on these two risk factors in order to find ways for reducing and eliminating them in postpartum mothers.

Conclusion
The current study showed that the most common cause of postpartum readmission was febrile complications and bleeding, which were observed more commonly among women with CS. Also, these women had longer hospital stay and a greater number of morbidities.

Research limitations
The data were extracted from the patient records and are therefore subject to miscoding and unreported information. Also, the data do not provide information on clinical management parameters including medications, vital signs, laboratory values, or severity of illness conditions, all of which could have influenced the risk of postpartum readmission. Although Ahvaz has a diverse and large population, examining data from only teaching hospitals may affect the generalizability of the results. Given that metritis and postpartum hemorrhage were the primary causes of readmission in women following cesarean and vaginal deliveries in this study, implementing strategies to mitigate these risk factors could significantly decrease the overall readmission rate. Therefore, future studies are recommended to accurately focus on these risk factors.

Suggestion for future research
Further research is essential to comprehensively understand the risk factors associated with metritis and postpartum hemorrhage.

Conflict of Interest
There was no conflict of interest in this manuscript.