Abstract

Objective: To assess the obstetric risk factors of postpartum urinary retention (PPUR) after vaginal delivery. Study design: A case control analytical study. Materials and methods: Out of 1500 women included in the study, 258 women (17.2%) who had postpartum urinary retention were cases and 1242 women (82.8%) who did not were controls. Postpartum urinary retention was defined as the inability to void within 6 hours of delivery or who had postvoid residual bladder volume ≥150 ml. Logistic regression analysis was used to identify the risk factors of post-partum urinary retention. Result: Prolonged duration of the second stage of labor [Odds Ratio (OR)=1.0858, 95% Confidence Interval (CI) for OR=1.0640 to 1.1080, p value<0.001], presence of episiotomy (OR=90.2116, 95% CI for OR=13.3786 to 608.2946, p value<0.001), perineal laceration (OR=104.3896, 95% CI for OR=32.6871 to 333.3784, p value<0.001), and birth weight of >4000 g for the newborn(OR=136.2499, 95% CI for OR=45.8096 to 423.7436, p value<0.001), were found to be independent risk factors for PPUR after vaginal delivery. Conclusion: Post-partum urinary retention is a relatively common disorder which may cause permanent harm to bladder function. The obstetrician may avoid this complication by the knowledge of risk factors. To determine whether routine postpartum bladder scanning is cost-effective and beneficial, further studies are needed.

Introduction

Voiding difficulty or post-partum urinary retention (PPUR) is a common but disturbing phenomenon in the immediate post-partum period. The exact incidence of PPUR is unknown but in the literature, the incidence of PPUR varies between 0.05% to 37% ^[1]. However, the approximate incidence is likely to be higher since the majority of cases frequently remain unreported.

PPUR is not clearly defined in literature and is often described as absence of spontaneous micturition after 6 hours of vaginal delivery or no spontaneous micturition after removal of the indwelling catheter after LSCS ^[2]. Yip et al has classified postpartum urinary retention into overt and covert retention ^[3]. Women with post-void residual bladder volume (PVRBV) of more than 150 ml on ultrasound screening or catheterization, without any retention symptoms are said to have covert urinary retention. Overt urinary retention refers to the inability to void in presence of signs and symptoms of urinary retention.

The causes of PPUR have been postulating as physiological changes during pregnancy, perineal trauma, nulliparity, regional analgesia, instrumental delivery, and prolonged labor ^[3]. However, the pathophysiology is poorly known. It can be due to physiological, neurological, and mechanical processes in the postpartum period. Inappropriate or delayed diagnosis and management of PPUR can lead to bladder dysfunction, urinary tract infection, and catheter-related complications ^[4]. Every post-delivery woman should void within 6 hours, as per RCOG Incontinence in Women Study Group. Both NICE guidelines on postnatal care and the WHO technical consultation on postpartum and postnatal care state that if there is no voiding within 6 hours of birth and the voiding struggle is not successful, the bladder volume should be measured ^[5]. Post void residual bladder volume (PVRBV) is determined after passing a urethral catheter to drain the bladder, but this is a painful procedure and is associated with risk of infection or trauma. Ultrasound is non-invasive and easily available alternative to diagnose post-void residual urine volume. For comparison of published data and testing purposes, the most widely used volume is > 150 ml for diagnosing post-partum urinary retention ^[6]. In this study, we aimed at assessing the obstetric risk factors that can predict the occurrence of PPUR in women with vaginal delivery and prevent its complications.

Materials and Methods

The study was conducted in a tertiary care hospital from December 2018 to May 2020. The institutional ethics committee approved the study. 1500 women with uncomplicated pregnancies who had term singleton vaginal delivery were included in the study. Written and informed consent was taken from all the participants of the study. Participant data including age, parity, obstetric history and intra-partum data such as gestational age at onset of labour, spontaneous or induced labor, use of oxytocin, epidural analgesia, duration of first, second, third stage of labour, fundal pressure during the second stage of labour, instrumental delivery, birth weight (babies with birth weight >4 kg defined as macrosomic baby ), head circumference measurement of new born, perineal laceration, episiotomy and postpartum urinary symptoms (dysuria, frequent urge to urinate without being able to pass much urine, and feeling like bladder not completely empty) was recorded.

All women underwent transabdominal ultrasound immediately after first micturition in the postpartum period to assess PVRBV. To achieve a longitudinal and transverse scan of the bladder, the transducer was placed in the midline on the top of the symphysis pubis. The widest diameter was measured in cm in the transverse scan (D1), the anteroposterior diameter in cm in the longitudinal scan (D2) and the cephalocaudal diameter in cm in the longitudinal scan (D3). Estimated PVRBV was calculated by using the formula D1×D2×D3×0.7 ^[7]. Women with estimated PVRBV ≥150 mL or who were unable to micturate within 6 hours after vaginal delivery were defined as the cases. Women who had an estimated PVRBV<150 mL were defined as the controls.

1. Statistical analysis: Statistical analysis was done with the help of SPSS Version 26. The normal distribution of the variables was analysed. Continuous variables with normal distribution are presented as mean ± standard deviation. Median (minimum-maximum) value was used where a normal distribution was absent. Quantitative variables are given as number (percentage). Statistical comparison was carried out by chi-square (χ2), and independent sample t-tests where appropriate. Logistic regression model was performed to analyse risk factors for PPUR. P<0.001 was considered statistically significant. Odds ratio and corresponding 95%confidence intervals are reported. Significant variables were analysed by bivariate and multivariate logistic regression analyses to determine which factors were independently associated with PPUR.

Results

In our study, out of the 1500 patients recruited, 258 patients had PPUR with an overall incidence of 17.2%. Of the 258 women in the study 96.12% of patients had covert urinary retention while 3.88% of women were diagnosed to have overt retention. The characteristics of women and newborns are listed in Table 1. There were no statistically significant differences between patients with or without PPUR regarding age, gravida, parity, gestational age, time to 1st void, duration of first and third stage of labour, induction or augmentation of labour, fundal pressure, labour analgesia or presence of episiotomy. However, the mean birth weight of newborns was found to be statistically significantly higher in women with PPUR being 3969.44 ± 560.055g as compared to 3147.192 ± 400.483g in women. Also, the greater head circumference in patients with PPUR was found to be statistically significant being 34.53 ± 3.235 cm as compared to 32.94 ± 3.641 cm in patients without PPUR. Regarding obstetric characteristics, there was no significant differences between the two groups but the duration of second stage of labour was statistically significantly higher being 133.61 ± 27.109 min in patients with PPUR as compared to 79.18±23.442 min in patients without PPUR. The presence of perineal lacerations was also statistically significantly higher in patients with PPUR (94.57%) as compared to 1.37% in patients without PPUR. More women with PPUR (73.26%) gave birth to macrosomic infants as compared to women without PPUR (0.016%) and the difference was statistically significant.

Logistic regression analysis of various risk factors of PPUR show that prolonged duration of second stage of labour, presence of episiotomy, perineal lacerations and birth weight >4000g for the newborn were significant risk factors to predict PPUR after vaginal delivery.

Figure 1. Figure 1: ROC curve analysis of 2nd stage of Labour

Figure 2. Figure 2. ROC curve analysis of Birthweight

Table 1. Table 1 : Characteristics of patients and labour with or without PPUR

	No PPUR n=1242	PPUR n=258	P value
Age (in yrs)	28.67 ± 6.203	28.11 ± 6.398	0.1896
Primigravida	49	160	0.4351
Primipara	168	90	0.4025
Gestational age (in days)	280.05 ± 8.337	279.05 ± 6.235	0.1806
Birth weight (in grams)	3147.192 ± 400.483	3969.44 ± 560.055	0.0001
Head circumference (in cm)	34.53 ± 3.235	32.94 ± 3.641	0.0001
Time to first void (in hrs)	3.79	3.67	0.29
PVRBV (ml)	87.94± 63.27	173.11± 75.32	0.0001
1st stage duration (in min)	534.98 ± 206.850	527.59 ± 202.022	0.6002
2nd stage duration (in min)	79.18±23.442	133.61 ± 27.109	0.0001
3rd stage duration (in min)	34.63 ± 14.768	35.80 ± 14.572	0.2409
Labour augmentation with oxytocin	599 (48.22%)	135 (52.32%)	0.2311
Labour induction with oxytocin or misoprostol	639 (51.44%)	123 (47.67%)	0.2744
Labour analgesia	620 (49.91%)	136 (60.46%)	0.227
Fundal pressure	416 (33.49%)	94 (36.43%)	0.201
Macrosomic newborn (>4000g)	20 (0.016%)	189 (73.26%)	0.0001
Episiotomy	665 (53.54%)	149 (57.75%)	0.2430
Perineal laceration	14 (1.37%)	244 (94.57%)	0.0001

Table 2. Table 2 : Logistic regression analysis of risk factors for PPUR

Variable	Wald	P	Odds ratio	95% CI
Parity	2.4100	0.1206	1.9300	0.8414 to 4.4269
Analgesia during labour	0.1324	0.7160	0.8767	0.4314 to 1.7816
Duration of the first stage	2.5793	0.1083	1.0018	0.9996 to 1.0040
Duration of the second stage	63.2812	<0.0001	1.0858	1.0640 to 1.1080
Labour induction with IV oxytocin	0.5724	0.4493	1.3247	0.6394 to 2.7446
Fundal pressure	3.7161	0.0539	0.2657	0.0691 to 1.0224
Episiotomy	21.3781	<0.0001	90.2116	13.3786 to 608.2946
Perineal laceration	61.5592	<0.0001	104.3896	32.6871 to 333.3784
Macrosomic newborn	72.0700	<0.0001	136.2499	43.8096 to 423.7436
Time birth to the first void hours	9.2592	0.0023	0.4608	0.2797 to 0.7590

Discussion

In our study it was found that PPUR is a relatively common occurrence with an incidence of 17.2%. In the literature, the incidence of PPUR varies widely between 0.05% to 37% ^[8-9]. The difference may be due to different study designs and underdiagnosis of covert urinary retention. Overt retention is easily detected, although covert retention is only known by ultrasound or catheterization, as there are no symptoms in most women. The average maternal age has been found to be between 25 and 28 years in the literature ^[3]. In this study, the mean age of the patients with post-partum urinary retention was 28.11 ± 6.398 years compared to 28.67 ± 6.203 years in those without urinary retention. Many different obstetrical risk factors have been considered for the pathogenesis of PPUR in the literature but the exact etiology of PPUR is not known. Nulliparity is often perceived as a risk factor ^[10,1]. They are exposed to pelvic floor tenderness and pudendal nerve damage during vaginal birth. In the literature, the incidence of PPUR has been found to be higher in primigravida than in multigravida ^[9,11]. However, in the present study, parity was not a risk factor for PPUR. Prolonged stages of labour may result in PPUR. The possible mechanism is applied mechanical strength leading to pelvic nerve damage which results in neurologic impairment of the bladder. Kekre et al noted that the periods of the first and second phases of labour were directly related to the residual amount of postpartum urine, and a higher incidence of PPUR was also correlated with the labour period of 700 minutes ^[12]. We also identified prolonged second stage of labour as a risk factor for PPUR. Delivery of a marosomic newborn was also identified as a risk factor of PPUR in our study. The rise in abdominal pressure with a macrosomic baby, may lead to pelvic and pudendal nerve damage. This causes neurologic impairment of micturition and, therefore, urinary retention. This is similar to the study by Cavkaytar S et al but in contrast to the study by Polat et al which showed that fetal birth weight does not increase the risk of PPUR ^[13,14]. In contrast to our findings, Pifarotti et al detected fundal pressure as a major risk factor for PPUR development during the second stage of labour ^[15]. We also found a higher incidence of PPUR in women with perineal lacerations and episiotomy than in women without them. Episiotomy may cause edema in the perineal region and hence result in damage to the perineal nerve innervation, leading to PUR. Musselwhite et al reported that second- and third-degree perineal tears, which might result in reflex urethral spasm, had a relationship with PPUR. However, the same study showed that episiotomy had no impact on PPUR ^[16]. In contrast, Yip et al reported that perineal trauma had no effect on the incidence of PPUR ^[3]. There is insensitivity of the bladder muscle due to the hormonal changes. This together with bladder edema and the injury to the pelvic nerve plexus (leading to neuropraxia) from compression of the presenting part, increases the chances of PUR after delivery. Early identification and treatment results in recovery of most of the cases with PUR. In a study on 11,332 women, Carley et al found that 45% of symptomatic PPUR resolved within 48 hours and 25% of women had persistence for more than 72 hours ^[9]. In case of delay in detection of PPUR, it can result in bladder under-activity, retention, recurrent urinary tract infections and prolonged voiding dysfunction. Many short-term complications of PPUR have been mentioned, but it is uncertain whether PPUR results in any long-term morbidity. Yip et al found no significant difference between women with and without urinary retention in a four year follow up in terms of urinary stress incontinence, fecal incontinence, frequency, urgency, nocturia and coital incontinence ^[17]. Mulder et al, did not find any difference in voiding difficulty or the development of lower urinary tract symptoms in a 1-year follow-up of women with covert PUR defined as PVRBV >150 mL ^[18]. No guidelines recommend routine bladder scanning for the diagnosis of PPUR, due to the size of the uterus after delivery, and the accuracy of USG measurements of residual volume is debatable ^[19]. The benefits and cost-effectiveness of routine post void bladder screening can be confirmed only by further research. Further studies are also needed to establish a cut-off for defining covert urinary retention to assess long term complications such as voiding dysfunction.

Conclusions

To conclude, PPUR is a relatively common condition that can cause bladder dysfunction. Longer second stage of labor, delivery of a macrosomic newborn, the presence of episiotomy and perineal lacerations are significant risk factors for the development of PPUR. Awareness of risk factors may allow the obstetrician to prevent this complication.

Declarations

Consent

Written and informed consent was obtained from all the participants of the study.

Ethics approval

Approval for the study was obtained from Tata Main Hospital Institutional Ethics Committee.

Ethics Committee Approval document no. TMH/FRM/QMS/ALL/19

List of abbreviations

OR: odds ratio

CI: Confidence interval

PPUR: post-partum urinary retention

PVRBV: Post void residual bladder volume

Conflicts of Interest

The author(s) declare(s) that there is no conflict of interest regarding the publication of this paper.

Funding Statement

None

Authors' contributions

SA-Study design, data collection, preliminary draft. OS- supervising, final draft. All authors read and approved the final manuscript.

Acknowledgments

None

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