Correlation between postpartum pelvic floor dysfunction and vaginal microecological imbalance in late pregnancy

Abstract

Objective

Pelvic floor dysfunction (PFD) seriously affects women’s physical and mental health. Pregnancy and childbirth are recognized as high-risk factors for PFD, and studies have shown that vaginal microenvironmental disorders can promote the development of pelvic organ prolapse. In this study, we intend to investigate whether the changes in vaginal microecology during pregnancy affect the pelvic floor function and participate in the development of postpartum PFD, and provide a basis for the prevention and treatment of PFD.

Methods

A total of 358 full-term mothers who delivered in Third Xiangya Hospital, Central South University from November 2019 to April 2020 were selected and underwent review 6 to 8 weeks after delivery. The pelvic floor structures were examined using pelvic floor ultrasound, and ultrasound values were measured at rest and at maximum Valsalva maneuver. One hundred and seventy women with PFD were assigned in a PFD group, and 188 women without PFD were assigned in a control group. The clinical data of all mothers were collected, and the clinical data and the results of microecological testing for vaginal secretions after 36 weeks of gestation and before delivery were compared between the 2 groups. The correlation of PFD with leucorrhoea cleanliness, lactobacillus level, bacterial vaginosis (BV), and vulvovaginal candidiasis (VVC) was analyzed, and logistic regression analysis was used to screen for independent risk factors for PFD.

Results

The incidences of VVC, BV, Lactobacillus vaginalis deficiency, and leucorrhoea cleanliness ≥III° were all higher in the PFD group than those in the control group (P<0.05). Among them, leukocyte cleanliness ≥III°and lack of Lactobacilli in the vagina were independent risk factors for the development of PFD, while VVC and BV were not independent risk factors for the development of PFD.

Conclusion

Postpartum PFD is related to vaginal microecological imbalance in late pregnancy, among which Lactobacillus vaginalis deficiency and leucorrhoea cleanliness ≥III° are independent risk factors for the occurrence of PFD. Therefore, pregnant women with Lactobacillus vaginalis deficiency and leucorrhoea cleanliness ≥III° in late pregnancy should pay attention to the occurrence of postpartum PFD, and early diagnosis and effective intervention of postpartum PFD should be enhanced.

Pelvic floor dysfunction (PFD) is a general term for a series of disorders that result from changes in the position and structure of the pelvic floor organ tissues^[1], which seriously affect the physical and mental health of women. The lifetime probability of developing pelvic organ prolapse (POP) in women is about 50%, and the probability of needing surgery for POP or stress urinary incontinence (SUI) is between 11% and 19%^[2]. With the opening of China’s three-child policy, the incidence of postpartum PFD will increase accordingly. Pregnancy is a special physiological period for women, when all organs and systems of the body undergo certain changes, including the reproductive tract and vaginal micro-ecosystem. It has been shown that disturbances in the vaginal microenvironment can promote the development of pelvic organ prolapse^[3]. It is unclear whether alterations in vaginal microecology during pregnancy also affect pelvic floor function and be involved in the development of postpartum PFD. There are few reports on this topic. Therefore, this study aims to analyze the correlation between postpartum PFD and vaginal microecological imbalance in late pregnancy to provide a basis for the prevention and early intervention of PFD.

1. Subjects and methods

1.1. Study population

A total of 358 full-term mothers who delivered in Thild Xiangya Hosptial, Central South University from November 2019 to April 2020 were selected and underwent review 6 to 8 weeks after delivery. The pelvic floor structures were examined using pelvic floor ultrasound, and ultrasound values were measured at rest and at the time of maximum Valsalva. One hundred and seventy women with PFD were assigned in a PFD group, and 188 women without PFD were assigned in a control group.

Inclusion criteria: 1) Full-term mothers who had regular obstetric examinations during pregnancy and delivered in our hospital; 2) Coming to our hospital for pelvic floor function assessment 6 to 8 weeks after delivery; 3) Having complete case information. Exclusion criteria: Women with a history of PFD, serious pregnancy complications and comorbidities, history of mental disorders, history of pelvic floor surgery, chronic cough and puerperal infection. This study involving human samples was approved by the Ethics Committee of Third Xiangya Hospital, Central South University (No. 22027).

1.2. Research methodology

We collected of general maternal clinical data, as well as microecological results of vaginal secretions in late pregnancy (36 weeks’ gestation to prenatal). Sampling method: Vaginal secretions were obtained from the upper 1/3 of the lateral wall of the vagina with a sterile cotton swab and placed in a test tube to analyze the vaginal microecological situation according to the results of the automated analysis instrument. All women underwent pelvic floor ultrasound examination 6 to 8 weeks after delivery, and the corresponding ultrasound values (residual urine volume, thickness of the forceps, distance of the bladder neck from the reference line, angle of urethral tilt, posterior angle of the vesicourethra and observation of the presence of an open internal urethral opening, rectal distension, uterine prolapse, and bladder bulge in the maximal Valsalva state) were measured at rest and at the time of maximum Valsalva. All data were measured 3 times, the average value was taken, and the images were stored. Each value has its own ultrasound diagnostic criteria^[4]. Uterine cervix <3.0 cm from the level of the inferior border of the pubic bone or movement >2.0 cm in the Valsalva action state compared to the rest is diagnosed as uterine prolapse. The height of the localized bulge of the anterior rectal wall >0.5 cm is diagnosed as rectal bulge. When the posterior wall of the bladder and urethra protrudes into the vagina and its lowest point reaches the inferior border of the pubic symphysis, it is diagnosed as anterior vaginal wall prolapse. The plane of the fissure of the anal levator muscle in the 4-dimensional image which showed V-shaped hyperechoic or hyperechoic interruption with hypoechoic insertion is diagnosed as a puborectal muscle tear. Bladder neck below the inferior border of the pubic bone in the Valsalva state or bladder neck movement >1.5 cm when compared to the rest is diagnosed as bladder neck bulge.

1.3. Statistical analysis

All data were processed using SPSS 19.0 statistical analysis software. The measurement data were expressed as mean±standard deviation ( $\overline{x}$ ±s) and compared by t-test.The χ² test was used for the count data. The Fisher’s method was used when T (theoretical frequency) was <1 and the corrected χ² test was used when 1≤T<5. Multivariate analysis was performed using logistic regression analysis with α=0.05. P<0.05 was considered statistically significant.

2. Results

2.1. Comparison of general information between the 2 groups

In the PFD group，there were 10 cases of bulging bladder type I, 73 of bulging bladder type II, 15 of bulging bladder type III, 62 of dilated anal raphe only, and 10 of open posterior horn of the bladder urethra only. There were no statistically significant differences in age, delivery mode (cesarean section rate), perineal incision rate, and pre-pregnancy body mass index (BMI) between the 2 groups (P>0.05, Table 1 and 2).

Table 1.

Comparison of general information of pregnant women between the 2 groups ( $\overline{\mathit{x}}$ ±s)

Group	n	Age/year	Pre-pregnancy BMI/(kg·m2)
PFD group	170	30.38±3.418	21.13±3.48
Control group	188	29.82±3.462	20.58±3.19

PFD: Pelvic floor dysfunction.

Table 2.

Comparison of mode of delivery and perineal conditions between the 2 groups

Group	n	Mode of delivery/[No.(%)]		Perineal operation/[No.(%)]
		Cesarean delivery	Vaginal delivery	Perineal incision	Unincised perineum
PFD group	170	65(38.2)	105(61.8)	12(7.1)	158(92.9)
Control group	188	82(43.7)	106(56.3)	14(7.4)	174(92.6)
χ²		1.068		0.020
P		0.301		0.888

PFD: Pelvic floor dysfunction.

2.2. Comparison of pregnancy, delivery times, and birth weight of newborns between the 2 groups

Pregnancy and delivery times in the PFD group were more than those in the control group (P<0.05). The incidence of newborns with birth weight ≥3.5 kg was significantly higher in the PFD group than that in the control group (P<0.05, Table 3).

Table 3.

Comparison of pregnancy and delivery times and birth weight of newborns between the 2 groups

Groups	n	Pregnancy times/[No.(%)]			Delivery times/[No.(%)]		Neonatal weight/[No.(%)]
		1-2	3-4	≥5	1	≥2	≥3.5 kg	<3.5 kg
PFD group	170	124(72.94)	41(24.12)	5(2.94)	94(55.29)	76(44.71)	67(39.41)	103(60.59)
Control group	188	154(81.91)	26(13.83)	8(4.26)	128(68.09)	60(31.91)	55(29.26)	133(70.74)
χ²			6.399		6.200		4.099
P			0.041		0.013		0.043

PFD: Pelvic floor dysfunction.

2.3. Comparison of maternal vaginal microecology between the 2 groups

The incidence of bacterial vaginosis (BV) and vulvovaginal candidiasis (VVC) was higher in the PFD group than that in the control group (both P<0.01). No trichomonas vaginitis patients were detected in the PFD group and the control group in the late pregnancy. The incidence of leucorrhea cleanliness ≥III° without specific infection was higher in the PFD group than that in the control group (P<0.001). The incidence of Lactobacillus vaginalis deficiency was significantly higher in the PFD group than that in the control group (P<0.001, Table 4).

Table 4.

Comparison of the incidence of BV, VVC, leucorrhea cleanliness ≥III°, and Lactobacillus vaginalis deficiency in the vagina between the 2 groups

Groups	n	BV/[No.(%)]		VVC/[No.(%)]		Leucorrhea cleanliness/[No.(%)]		Lactobacillus vaginalis/[No.(%)]
		+	-	+	-	≥III°	<III°	not few	few or no
PFD group	170	10(5.88)	160(94.12)	40(23.53)	130(76.47)	72(42.35)	98(57.65)	56(32.94)	114(67.06)
Control group	188	1(0.53)	187(99.47)	11(5.85)	177(94.15)	34(18.09)	154(81.91)	108(57.45)	80(42.55)
χ²		8.581		22.838		25.226		21.596
P		0.003		<0.001		<0.001		<0.001

BV: Bacterial vaginosis; VVC: Vulvovaginal candidiasis; PFD: Pelvic floor dysfunction.

2.4. Results of multiviriate regression analysis of PFD

Logistic regression analysis was performed on the above statistically significant results to find the independent risk factors for PFD. The results showed that leukocyte cleanliness ≥III° and Lactobacillus deficiency in the vagina were independent risk factors for the occurrence of PFD (both P<0.05), whereas VVC, BV, pregnancy and delivery times, and neonatal weight ≥3.5 kg were not independent risk factors for the occurrence of PFD (all P<0.05).

Table 5.

Results of multiviriate logistic regression analysis of PFD

Influencing factors	b	S b	Wald	P	OR	95% CI
BV	1.268	1.074	1.394	0.238	3.555	0.433~29.186
VVC	0.316	0.410	0.594	0.441	1.372	0.614~3.064
Leukocyte cleanliness ≥III°	1.079	0.401	7.225	0.007	2.941	1.339~6.459
Pregnancy times	0.044	0.150	0.084	0.771	1.045	0.778~1.403
Delivery times	0.235	0.310	0.575	0.448	1.265	0.689~2.324
Neonatal weight ≥3.5 kg	0.461	0.258	3.202	0.074	1.586	0.957~2.629
Lactobacillus vaginalis deficiency	0.931	0.395	5.557	0.018	2.536	1.170~5.499

PFD: Pelvic floor dysfunction; BV: Bacterial vaginosis; VVC: Vulvovaginal candidiasis.

3. Discussion

Currently, pregnancy and childbirth are recognized as the 2 major risk factors for the development of PFD^[5]. Previous literature^[3] has shown that factors associated with pregnancy and delivery causing PFD are gestation, delivery, large fetal weight, and delivery mode. The present study showed that the incidences of gestation, delivery, and neonatal weight ≥3.5 kg are higher in the PFD group than those in the control group, which is consistent with the current general opinion and the findings of Castro-Pardiñas^[6]. However, in this study, there was not significant difference between the 2 delivery methods, and PFD can also occur in women who delivered by cesarean section. According to the previous study^[7], women in late pregnancy already show significant changes in the anatomy of the pelvic floor, such as the enlargement of the fissure of the genital tract, the increase of the fissure area of the anal levator muscle, the increase of the bladder posterior angle, and the increase of urethral inclination. The pelvic floor is gradually weakened by these physiological changes. Therefore, the impairment of pelvic floor function due to pregnancy itself already exists before the choice of delivery method. The delivery mode has an effect on postpartum pelvic floor function. Since this study focused on the correlation between PFD and vaginal microecology, the effect of delivery mode was set aside in this study. In future studies, we can expand the sample size to analyze the effect of delivery mode (vaginal delivery, elective cesarean, and intermediate cesarean) on postpartum pelvic floor function.

It has been found that imbalance in vaginal microecology is also involved in the development of PFD^[3]. The vaginal microecosystem which is specific to the female genital tract includes 4 components: The microecological flora of the vagina, the anatomical structure, the endocrine regulatory function of the organism, and the local mucosal immune function^[8]. The results of this study showed that the incidences of BV, VVC, leukorrhea cleanliness ≥III°, and intravaginal Lactobacillus vaginalis deficiency were higher in the PFD group than those in the control group, suggesting that the occurrence of PFD is associated with vaginal microecological imbalance in late pregnancy. Moreover, this study showed that leukorrhea cleanliness ≥III° and Lactobacillus vaginalis deficiency were independent risk factors for postpartum PFD.

The vaginal microecological environment of healthy reproductive-age women is dominated by Lactobacillus vaginalis, and more than 20 species of Lactobacillus have been found to be parasitic in the vagina, coordinating and cooperating with a variety of other microrganisms to maintain the balance of vaginal microecology^[9]. Lactobacilli can increase the resistance of the reproductive tract to the infection of pathogenic microorganisms by maintaining the acidic environment in the vagina, forming a protective bacterial film on the mucosal surface, preventing the invasion of pathogenic microorganisms, inhibiting the growth of other flora, and enhancing the immune response. The vaginal ecological imbalance rate of pregnant women was found to be significantly higher in pregnant women than that in non-pregnant women of the same age^[10]. Most women’s vaginal flora do not change significantly during pregnancy and Lactobacillus remains the dominant flora. With the increase of gestational weeks, estrogen gradually increases, vaginal epithelial cells proliferate, which can promote glycogen production and increase vaginal acidity. The excessively acidic vaginal environment is not conducive to the growth of Lactobacillus. The content of Lactobacillus gradually decreases, reducing the antibacterial capacity of Lactobacillus, increasing the number of non-Lactobacillus flora, and changing the composition of the flora, even leading to the multiplication of pathogenic microorganisms and causing vaginal inflammation^[9]. In addition, changes in hormone levels during pregnancy cause congestion and increased permeability of vaginal mucosal tissues, making it easy for pathogenic bacteria to invade and cause infection. Compared with non-pregnancy period, the colonization rate of vulvovaginal Pseudomonas aeruginosa increases 2-3 times in the vagina of pregnant women, mainly Pseudomonas albicans, which predisposes to VVC. The decrease of Lactobacillus in the vagina in middle to late pregnancy also results in the increase of pathogenic bacteria such as anaerobic bacteria and Gardnerella, which predispose to BV. Pathogenic bacteria can produce a variety of enzymes with destructive ability, such as collagenase and elastase, which have a destructive effect on the synthesis and breakdown of cellular proteins of pelvic floor tissues and the mechanical properties of pelvic floor tissues^[11]. Also, sex hormonal changes during pregnancy contribute to the shedding of vaginal epithelial cells, increased vaginal discharge, and changes in cleanliness. When the cleanliness is ≥III°, it indicates the presence of a large number of pathogenic microorganisms and inflammatory factors, which can be used as an indicator of vaginal infection and judged as the presence of vaginal microecological abnormalities, even if there is no clear pathogenic infection in the vagina by the test^[3]. Bao, et al^[3] also found that Lactobacillus vaginalis deficiency is one independent risk factor for PFD and that the increase of Lactobacillus level may be a protective factor for PFD, and the results of this study are consistent with it.

In recent years, Lactobacillus vaginal capsule preparations have been used clinically for the treatment of vaginitis, and they can optimize the vaginal flora and improve the pregnant outcomes in patients with BV in late pregnancy^[12]. A randomized controlled study found that the perimenopausal use of estrogen combined with Lactobacillus improved the degree of PFD and alleviated the signs and symptoms of SUI in middle-aged and older women^[13-14]. However, the possibility of using Lactobacillus vaginal capsules for the prevention of postpartum PFD in pregnant women with vaginal microecological imbalance in late pregnancy needs to be further explored.

In addition, in the PFD group of this study, there were 10 cases of bulging bladder type I, 73 of bulging bladder type II, 15 of bulging bladder type III, 62 of dilated anal raphe only, 10 cases of open posterior horn of vesicourethra only, and no other pelvic floor function abnormalities were seen, which may be related to the small sample size in this study, and only the ultrasound results at the 42nd day after delivery were counted in this study, so other pelvic floor function abnormalities may not be seen yet. In future studies, the sample size can be further expanded to analyze whether other pelvic floor function abnormalities exist, and the correlation between vaginal microecological imbalance and pelvic floor function abnormalities, to predict the types of postpartum pelvic floor function abnormalities according to different types of vaginal microecological imbalance, and then carry out more targeted clinical interventions, which is conducive to early diagnosis and effective intervention for postpartum PFD.

Funding Statement

This work was supported by the Natural Science Foundation of Hunan Province, China (2021JJ31012).

Conflict of Interest

The authors declare that they have no conflicts of interest to disclose.

AUTHORS’CONTRIBUTIONS

CHENG Chunxia Data analysis, paper design, writing, and revision; GUO Boyang, WU Wen, and MI Chunmei Data collection and analysis; LI Ruizhen and LI Xuhong Paper design, guidance, and revision. All authors read and agreed to the final text.

Note

http://xbyxb.csu.edu.cn/xbwk/fileup/PDF/2022111608.pdf