Risk factors for postpartum urinary retention after vaginal delivery among primiparous women: a retrospective case-control study

Abstract

Background

Postpartum urinary retention (PUR) usually occurs in the immediate postpartum period among the women after vaginal delivery. The recognition of risk factors may enable early and prompt diagnosis.

Methods

We conducted a retrospective matched case-control study to identify the risk factors for postpartum urinary retention in primiparous women after vaginal delivery between July 2016 and January 2024. All data were collected through our hospital’s electronic health record system. Demographics, gestational and delivery characteristics were compared between groups by using univariate and multivariate analyses to identify the risk factors for postpartum urinary retention.

Results

A total of 1275 primiparous women were included for analysis. In the multivariable logistic regression models, the risk factors were epidural analgesia (aOR 1.59, 95% CI 1.04 ~ 2.44, p = 0.032), duration of first stage (aOR 1, 95% CI 1 ~ 1, p < 0.001), duration of second stage (aOR 1.01, 95% CI 1.01 ~ 1.01, p < 0.001), episiotomy (aOR 2.23, 95% CI 1.68 ~ 2.95, p < 0.001), assisted delivery (aOR 2.15, 95% CI 1.34 ~ 3.45, p = 0.002) and postpartum haemorrhage (aOR 1.87, 95% CI 1.01 ~ 3.46, p = 0.047).

Conclusion

Postpartum haemorrhage was also associated with PUR after vaginal delivery among primiparous women in addition to the frequently proposed risk factors such as epidural analgesia, labor duration, episiotomy and assisted delivery. Manual removal of placenta or placental membranes was associated with a lower rate of PUR.

Background

Postpartum urinary retention usually occurs in the immediate postpartum period among the women after vaginal delivery. Estimates of the incidence of PUR vary widely, and voiding difficulties persist more frequently than previously assumed. Urinary retention has already been one of the risk factors for emergency postnatal maternal readmissions [1]. Early diagnosis and timely intervention can efficiently reduce the consequences such as persistent urinary retention and postpartum hemorrhage. Therefore, obstetric awareness, early active management, and developing management strategies in the postpartum period are very important and might preclude lower urinary tract morbidity [2].

Recognition of risk factors can facilitate early and prompt diagnosis. However, the independent risk factors for PUR vary and are often limited by confounding factors. Additionally, only 17.1% of obstetrics and gynecology residents received formal didactic approach on PUR management [3]. Therefore, scenarios concerning PUR were difficult to be recognized successfully.

Risk factors for PUR such as prolonged labor duration, epidural anesthesia, operative vaginal delivery, episiotomy and macrosomia vary widely. Previous studies have revealed that instrumental delivery, extended labor duration, episiotomy, nulliparity, epidural analgesia, labor augmentation/induction, and perineal injury are significant risk factors for PUR [4, 5]. Additionally, maternal with a BMI of 30 kg/m² or more before delivery, meconium-stained amniotic fluid, vaginal nonoperative birth, mediolateral episiotomy, neonatal birth weight > 4,000 g and > 3,500 g were also identified as risk factors for PUR [6–8].

Nulliparity is the more frequently proposed risk factors and unalterable [4, 5, 7]. Although a retrospective cohort study identified nulliparity as a minor independent risk factors for PPUR [6]. The aim of this study was to identify the risk factors associated with PUR among primiparous women after vaginal delivery.

Materials and methods

We performed a retrospective matched case-control study to identify risk factors for postpartum urinary retention in primiparous women after vaginal delivery at Shandong Provincial Maternal and Child Health Care Hospital Affiliated to Qingdao University between July 2016 and January 2024. This study was approved by Ethics Committee of Shandong Provincial Maternal and Child Health Care Hospital Affiliated to Qingdao University, with the approval number:2024 − 105.

All data were collected though our hospital’s electronic health record system. The inclusion criteria included vaginal delivery, primipara, singleton pregnancy, gestational age ≥ 37 weeks and postpartum urinary retention. The exclusion criteria involved readmission due to PUR in the postnatal period, urinary retention diagnosed before delivery, and PUR after catheter removal that was immediately inserted after a vaginal delivery. The control group was created through matching of women without PUR who delivered in every January from 2016 to 2024. The matching criteria included vaginal delivery, primipara, singleton pregnancy, gestational age ≥ 37 weeks and without postpartum urinary retention.

According to our hospital practice, the woman was regularly encouraged to successfully void during the first-second stage of labor and before delivery. If the bladder is distended and voiding is not possible, catheterization is indicated. The ultrasound scanning is routinely conducted within 24–48 h after delivery or on the day of discharge (day 2 or 3 postpartum) to assess the status of the uterus and residual urine. In this study, PUR including overt PUR and covert PUR. The overt PUR is diagnosed as the inability to void ≥ 6 h after vaginal delivery. And the covert PUR is diagnosed by a postvoid residual bladder volume of ≥ 150 mL measured by ultrasound after a spontaneous void [9]. For vaginal delivery, postpartum haemorrhage, typically defined as blood loss amounting to 500 mL or more within 24 h of birth.

Statistical analyses were performed with the statistical software packages R 4.3.2 (http://www.R-project.org, The R Foundation) and the Free statistics analysis platform. Continuous variables were presented with the use of mean, standard deviation, quartile and ranges and categorical variables were summarized with counts and percentages. For the analysis of baseline characteristics, the statistical differences were examined using the t-test or one-way ANOVA for continuous variables and the chi-square or Fisher test for categorical variables. Univariable logistic regression analysis and multivariable logistic regression models were utilized to identify risk factors associated with PUR. Statistical significance was defined as p < 0.05.

Result

A total of 1275 primiparous women were included for analysis. Of 625 women with PUR, 436 women (69.76%) had overt retention and 189 (30.24%) women had covert retention. The demographics, gestational and delivery characteristics are presented in Table 1. No significant differences were noted in maternal age, gestational age, gravidity, BMI before pregnancy, BMI at delivery, gestational weight gain and induction of labour between two groups (p > 0.05). The use of epidural analgesia was 93.3% in the group with PUR and 86.8% in the group without PUR (p < 0.001). The mean duration of first stage of labor was 471.6 ± 179.8 min in the group with PUR and 429.5 ± 169.7 min in the group without PUR (p < 0.001). A similar situation exists in the duration of second stage of labor (63.9 ± 35.3 vs. 51.4 ± 26.7, p < 0.001). The incidence rate of episiotomy and assisted delivery in the PUR group was 50.2% and 17.4%, respectively, and was 24.6% and 4.6% in the group without PUR, these differences were found to be statistically significant (p < 0.001). Incidence of the postpartum haemorrhage in the group with PUR was higher than in the group without PUR (6.7% vs. 3.5%, p = 0.01). But the use of manual removal of placenta or placental membranes in the group without PUR was more than in the PUR group (3.1% vs. 0.5%, p < 0.001).

Table 1.

Demographics, gestational and delivery characteristics

Variables	Control group (n = 650)	PUR group (n = 625)	t/F/χ2	p-values
Maternal age (y)	28.9 ± 3.3	29.0 ± 3.2	1.09	0.297
Gestational age (wk)	39.7 (39.1, 40.3)	39.9 (39.1, 40.4)	2.299	0.129
Gravidity, n	1.0 (1.0, 1.0)	1.0 (1.0, 2.0)	0.821	0.365
BMI before pregnancy (kg/m2)	21.5 ± 3.1	21.5 ± 3.0	0.004	0.948
BMI at delivery (kg/m2)	27.0 ± 3.2	27.2 ± 3.3	1.231	0.267
Gestational weight gain (kg)	14.7 ± 5.0	15.0 ± 4.6	1.683	0.195
Induction of labour, n (%)				0.171*
Balloon catheter	174 (26.8)	166 (26.6)
Dinoprostone	0 (0)	4 (0.6)
Epidural analgesia, n (%)	564 (86.8)	583 (93.3)	14.955	< 0.001
Duration of first stage (min)	429.5 ± 169.7	471.6 ± 179.8	18.519	< 0.001
Duration of second stage (min)	51.4 ± 26.7	63.9 ± 35.3	50.746	< 0.001
Episiotomy, n (%)	160 (24.6)	314 (50.2)	89.579	< 0.001
Assisted delivery, n (%)	30 (4.6)	109 (17.4)	53.951	< 0.001
Estimated blood loss (ml)	300.0 (280.0, 320.0)	290.0 (260.0, 310.0)	20.99	< 0.001
Extensive vaginal or cervical tears need suture repair, n (%)	7 (1.1)	3 (0.5)		0.343*
Third-degree or more lacerations, n (%)	0 (0)	1 (0.2)		0.49*
Manual removal of placenta or placental membranes, n (%)	20 (3.1)	3 (0.5)	12.131	< 0.001
Pressure of the gauze pack on posterior fornix, n (%)	5 (0.8)	11 (1.8)	2.524	0.112
Postpartum haemorrhage, n (%)	23 (3.5)	42 (6.7)	6.666	0.01
Birth weight (kg)	3272.0 ± 339.1	3298.7 ± 350.0	1.903	0.168
Fetal macrosomia	11 (1.7)	16 (2.6)	1.157	0.282
Length of stay (d)	3.7 ± 1.1	4.7 ± 1.4	200.304	< 0.001

*Fisher’s exact test

Multivariable logistic regression models analysis results were show in Table 2. In the multivariable logistic regression models, the risk factors were epidural analgesia (aOR 1.59, 95% CI 1.04 ~ 2.44, p = 0.032), the duration of first stage (aOR 1, 95% CI 1 ~ 1, p < 0.001), the duration of second stage (aOR 1.01, 95% CI 1.01 ~ 1.01, p < 0.001), episiotomy (aOR 2.23, 95% CI 1.68 ~ 2.95, p < 0.001), assisted delivery (aOR 2.15, 95% CI 1.34 ~ 3.45, p = 0.002) and postpartum haemorrhage (aOR 1.87, 95% CI 1.01 ~ 3.46, p = 0.047). We found that the women with manual removal of placenta or placental membranes were less likely to suffer PUR (aOR 0.09, 95% CI 0.02 ~ 0.35, p < 0.001).

Table 2.

Multivariable logistic regression models analysis results

Variables	aOR	95% CI	p-values
Epidural analgesia	1.59	1.04 ~ 2.44	0.032
Duration of first stage	1	1 ~ 1	< 0.001
Duration of second stage	1.01	1.01 ~ 1.01	< 0.001
Episiotomy	2.23	1.68 ~ 2.95	< 0.001
Assisted delivery	2.15	1.34 ~ 3.45	0.002
Manual removal of placenta or placental membranes	0.09	0.02 ~ 0.35	< 0.001
Postpartum haemorrhage	1.87	1.01 ~ 3.46	0.047

aOR: Adjusted odds ratio

Discussion

In this retrospective case-control study, we observed that the risk factors for PUR after a vaginal delivery in primiparous women included epidural analgesia, the duration of first stage, the duration of second stage, episiotomy, assisted delivery and postpartum haemorrhage. Manual removal of placenta or placental membranes performed was associated with a lower rate of PUR.

Risk factors including epidural analgesia, labor duration, episiotomy and assisted delivery were frequently proposed. A case-control study reported that PUR was highly associated with epidural analgesia [10]. The incidence of postpartum urinary retention after delivery with epidural analgesia was 25.7%, and a prolonged second stage of labor was an independent risk factor for postpartum urinary retention in epidural analgesia deliveries [11]. It is well-known that the duration of labor was prolonged throughout the entire labor and the first stage in women with epidural analgesia during delivery. An increase in the active first stage duration is associated with maternal complications in the early postpartum period [12]. The use of epidural analgesia during delivery as a risk factor for PUR was easily understandable. The use of epidural analgesia related changes, including reduced bladder muscle tone, decreased feeling of bladder discomfort, decreased sensation of bladder fullness, lengthened duration of labor may contribute to PUR development.

Many previous studies showed that postpartum urinary retention was highly associated with operative vaginal delivery, mainly concerned with forceps delivery [10, 13–15]. A cross-sectional analytical study reported that 20.6% of women undergoing instrumental delivery developed postpartum urinary retention [16]. Episiotomy is also significant risk factor for PUR [4, 5]. A contemporary nationwide cohort study found that obstetrical anal sphincter injuries increased the odds of postpartum urinary retention by 3.60 times after adjusting for potential confounders [17]. Laceration were significantly associated with postpartum urinary retention [15]. Operative vaginal deliveries were accompanied by episiotomy or laceration. However, during vaginal delivery, obstetrical anal sphincter injuries are relatively rare. In this study, only one woman had experienced third-degree or more lacerations. It is unclear whether third-degree or more lacerations is an individual risk factor. A previous cross-sectional analytical study indicated that episiotomy increased the chances of developing PUR in nulliparous but not in multiparous women undergoing instrumental delivery [16]. Some previous studies also found that perineal edema or perineal hematoma were associated with PUR [10, 13, 14]. Operative vaginal delivery may lead to direct pelvic floor damage, bladder trauma, direct partial or complete nerve transection, periurethral and vulvar edema that results in PUR. The pain associated with operative vaginal delivery may also lead to PUR.

In addition to frequently proposed risk factors such as epidural analgesia, labor duration, episiotomy and assisted delivery, postpartum haemorrhage was associated with PUR after vaginal delivery among primiparous women in this present study. But we found that manual removal of placenta or placental membranes was associated with a lower rate of PUR. The reason may be that intermittent bladder catheterization was necessary before the manual removal of placenta or placental membranes according to our hospital practice and then reduce the PUR. Although some previous studies have reported that neonatal birth weight > 4,000 g and > 3,500 g were risk factors for postpartum urinary retention in women with vaginal delivery [7, 8]. We did not found that birth weight and fetal macrosomia were associated with PUR. The results were similar to those of a previous study, where there was no correlation between birth weight and PUR risk [4]. We found that postpartum haemorrhage was associated with PUR in this study. The reason may be that with immediate postpartum hemorrhage, the management such as bimanual compression, anterior perineal triangle hematoma and suture with obstetrical lacerations may lead to more pain which associated with urinary retention.

The strength of this study is the inclusion of primiparous women after a vaginal delivery. As most previous studies identified nulliparity as a risk factor for PUR, we excluded multiparous women to avoid its confounding effect. However, our study has several limitations. It is a retrospective study and might be underpowered due to potential biases and confounding variables. Being conducted in a single-center setting and following identical hospital protocol may limit its generalizability.

Conclusions

We found that postpartum haemorrhage was associated with PUR after vaginal delivery among primiparous women in addition to the frequently proposed risk factors such as epidural analgesia, labor duration, episiotomy and assisted delivery. More attention should be paid to the women who suffered postpartum haemorrhage. Manual removal of placenta or placental membranes was associated with a lower rate of PUR.

Abbreviations

PUR

Postpartum urinary retention

OR

Odds ratio

CI

Confidence interval

BMI

Body mass index

Author contributions

XM and WZ have made substantial contributions to data curation, formal analysis, investigation, methodology and writing-original draft. CW contributed to data curation, formal analysis and investigation. LP and SS have contributed to Conceptualization, Formal analysis, Project administration, Methodology, Software, Supervision, Visualization, Writing-review & editing.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Data availability

The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.

Declarations

Ethics approval and consent to participate

This study was reviewed and approved by Ethics Committee of Shandong Provincial Maternal and Child Health Care Hospital Affiliated to Qingdao University, with the approval number:2024 − 105. Informed consent was waived by Ethics Committee of Shandong Provincial Maternal and Child Health Care Hospital Affiliated to Qingdao University for this study because this was a retrospective study and the data are anonymous. All methods were carried out in accordance with the Declaration of Helsinki, relevant guidelines and regulations.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.