Vaginal birth changes the anatomical structure of the maternal birth canal and genital tract, and it alters women`s perceptions and body function. In our study, LAM trauma does not seem to change urogynecological perceptions of women after vaginal birth tremendously within the first months, although there arise some significant differences in women with and without LAM trauma. Therefore, other maternal, fetal and obstetrical factors have to be considered for the explanation of maternal complaints besides LAM trauma.
Differences in baseline characteristics within the cohort
For our study cohort, we found significant differences in the baseline characteristics of the different LAM state groups for the birth mode, the duration of the second stage of labor, and for the rate of epidural anesthesia, episiotomies, high-grade perineal tears, labial tears and anterior prolapse, depending on the time after birth respectively. These differences are probably due to an altered biomechanics of birth in the LAM trauma groups compared to women with an intact LAM. Women with a PAV or CAV had more often a vacuum-assisted birth at P1 than those women with an intact LAM or hematoma. It remains unclear, whether the performance of the vacuum-maneuver itself might have caused the damage or if the dimensions of the fetus in relation to the maternal birth canal were more often unfavorable resulting in the need for assisted vaginal birth. Damage due to the vacuum maneuver itself could have been due to a fast performance of the maneuver with too little time for the tissue to stretch and adapt or due to an unfavorable position and rotation of the child within the birth canal. In a recent publication of our group, we could not evaluate a significant maternal, fetal or obstetrical factor during vacuum maneuver associated to the incidence of LAM avulsions, but we could not control for the just mentioned factors there (20). Hence, the relation of the fetus and the birth canal and their adaptations to each other during the birth process might be crucial. The higher rate of episiotomies at P1 and P2 and higher rates of high-grade perineal tears at P2 as well as the longer duration of the second stage of labor at P1 in women with LAM trauma probably support this explanation. An unfavorable biomechanical interaction of the fetus and the birth canal might be associated with a prolonged and more complicated birth process and might lead to more interventions. Additionally, it is known that whenever tears in the posterior compartment or episiotomies are present, less tears in the anterior compartment occur, such as labial tears. Therefore, women with intact LAM and with fewer injuries in the posterior compartment might have had higher rates of labial tears in our cohort. The same was seen at P3 for labial tears.
Women with a hematoma or complete avulsion had less often an epidural anesthesia at P1 in this study. From biomechanical simulation studies one can conclude that a relaxed pelvic floor during birth with no additional co-activation of the pelvic floor muscles reduces the stretch forces on the LAM, as can be achieved by the application of an epidural anesthesia (21). A study of Youssef et al supports this statement, as it showed that a LAM co-activation was associated with a longer second stage of labor in nulliparous women (22). Hence, an epidural might have been protective regarding pelvic floor trauma in our cohort.
Strong associations for CAV and prolapse symptoms in later life are described in the literature many years after childbirth (13, 23, 24). We could find such an association already some months after birth in our cohort, with higher anterior prolapse rates in women with CAV.
Assessment of women`s complaints regarding the time before and during pregnancy
No significant differences between the four LAM state groups were assessed regarding the time before and during pregnancy, resembling a homogeneous cohort of women in our study. The incontinence rates found in our cohort are in accordance with the rates in the literature (25–27). Most women had no incontinence or prolapse symptoms before pregnancy, but reported about any of them in up to 4–64% during pregnancy. These numbers underline that pregnancy itself with its mechanical and hormonal changes alters the voiding and defecation function, and it influences the anatomical organ structures.
Assessment of women`s complaints 1–4 days after birth (P1)
Only women with a CAV were all more often affected regarding involuntary stool loss compared to the time before birth. The women in the three other groups reported an unchanged or even improved status. The higher number of affected women in the CAV group cannot be explained by the presence of a high-grade perineal tear, as the rates did not differ significantly between the groups. An explanation could be an altered anal sphincter and levator ani muscle function due to a possible nerve damage or pelvic floor muscle overdistension within the first days after birth rather than a structural muscle damage due to a more complicated birth in that CAV group as mentioned above. Weidner et al found a neuropathic injury of the levator ani muscle in 24–29% of women at 6 weeks and 6 months after childbirth respectively (28).
Only 10% of women in the intact LAM group had the feeling of a wider vaginal opening, whereas 75% did not feel any change after birth. In contrast, up to 28% in the CAV group had the feeling of a wider vaginal opening and 51–57% of women in the three LAM trauma groups feeling unchanged. A wider vaginal opening is caused either by a structural widening, for example by an avulsion of the LAM, or by a functional widening by overdistension of the genital hiatus and the vagina or by neuropathic injury (28). Besides the structural damage of the LAM in the CAV group, the functional widening by a longer second stage of labor in the LAM trauma groups could explain the higher number of women with the feeling of a wider vagina in the trauma groups. In addition, tissue characteristics and distension capabilities of the individual woman might substantially contribute to the altered body anatomy and perception.
Assessment of women`s complaints 6–10 weeks after birth (P2)
The rates of involuntary bowel gas loss did not differ significantly between the LAM state groups at P2 compared to the time before birth, although the rate of high-grade perineal tears was significantly higher in the CAV group with 6.7% vs. 0.6% in the intact LAM group. However, if women complained about involuntary bowel gas loss, the situation remained stable in about 82% of women in the intact LAM group, whereas 46–50% of women in the LAM trauma groups reported a higher frequency of uncontrolled bowel gas loss. Again, besides the structural damage of the anal sphincter, a functional impairment by for example nerve impairment might be crucial, and functional damage is more likely in complicated births. Interestingly, one third of women in the PAV group even reported an improvement of bowel gas loss. We do not have any explanation for this phenomenon.
Women in the LAM trauma groups had more often a weaker pelvic floor at P2 compared to the time before birth than women in the intact LAM group (52–57% vs. 25%). Besides, no woman in the LAM trauma groups mentioned a stronger pelvic floor, in contrast to 5% of women in the intact LAM group. As a defect of the pelvic floor muscle in form of a PAV or CAV negatively affects the performance of the LAM, this association seems comprehensible and is described in the literature as well (24).
Assessment of women`s complaints 6–9 months after birth (P3)
18–35% of women after vaginal birth had the feeling of something squeezing downwards into the vagina after birth. There were no significant differences regrading this rate between the three LAM state groups. However, in women who described this feeling, all of them described it being apparent more often in the intact LAM group, whereas all women in the PAV group and most women in the CAV group described the situation as unchanged. This is interesting, as we would have expected such a complaint more frequently in the CAV group with the higher rate of anterior prolapse, especially as this phenomenon is reported in the literature (23, 29). Hence, a functional problem of the pelvic floor with “just” overdistension of the LAM instead of avulsion could explain this phenomenon in the intact LAM group. Unfortunately, overdistension of the genital hiatus was not evaluated with this study, so we cannot proof this idea. Besides, the number of women in the groups regarding this topic was very small, and conclusions need to be drawn with great caution.
Although women in the CAV group trained their pelvic floor more frequently, they suffered more often from an anterior prolapse than women in the PAV or intact LAM group. Hence, pelvic floor training cannot completely compensate the anatomical defect set by a CAV, but maybe can improve the extent and rate of prolapse in this group.
85–91% of women had sexual intercourse 6–9 months after birth, which is comparable with other studies showing that 89% of women resume sexual activity within 6 months of giving birth (30). Of those women, 60–83% reported an unchanged situation regarding sexual satisfaction. Nevertheless, 20–29% of women in the intact LAM and PAV group reported a reduced satisfaction compared to just 5.6% in the CAV group. 20% of women in the intact LAM group even had an increased satisfaction in contrast to none in the PAV and CAV group respectively. In the literature, a comparable reduction of sexual function and satisfaction is reported after vaginal birth in comparison to the pre-pregnancy period, with sexual dysfunction rates of up to 64% at 6 months after birth (31). Other studies report that sexual function after birth is not altered by pelvic floor muscle strength or mode of delivery, but by the presence of high-grade perineal tears (30, 32, 33). The association of sexual function and satisfaction to the presence of a LAM avulsion remains controversial (29, 34).
Complaints about urinary incontinence changed over the course of pregnancy and the postpartum period. 36–51% of women declared urinary incontinence during pregnancy, 13–28% at P1, 27–33% at P2 and 18%-45% at P3, with 18% in the intact LAM group and 40–45% in the LAM trauma groups. The improvement might be due to a natural recovery of the nerve structures of the pelvic floor and bladder, intrinsic improvement of pelvic floor muscle function and effects of pelvic floor muscle training. In contrast to the higher rate of urinary incontinence in women with LAM trauma in our study, other studies found no differences in stress urinary incontinence after vaginal birth in women with or without LAM trauma (35, 36). A similar trend and course can be seen for flatus incontinence in our study. It was the highest during pregnancy (43–64%), with a decrease over time from 39–56% at P1 to 24–37% at P2 and to 18–30% at P3. Prolapse symptoms were found in 16–24% during pregnancy, in 7–48% at P1, in 12–27% at P2 and in 9–40% at P3, with women in the LAM trauma groups being more often affected, especially women with CAV. However, women with intact LAM were also affected. Therefore, prolapse symptoms are not solely associated to structural LAM defects, but also to functional impairments, as for example the lower capability to recruit and control pelvic floor muscles. Stool incontinence was more or less stable, with 3–5% during pregnancy, 3–12% at P1, 1.9–5.3% at P2 and 0–5% at P3.
A strength of our study is definitely the longitudinal, prospective design with antenatal inclusion of the participants into the study, a small dropout rate regarding the LAM assessment 6–10 weeks after birth, and the validated assessment methods. Nevertheless, a limitation is the small number of women with LAM trauma at all assessment periods and the small cohort of women with intact LAM at P3 for comparison. For a more precise evaluation of the possible causes of women`s complaints it would be necessary to not only check for structural LAM trauma, but even for functional trauma. The dimensions of the genital hiatus should be examined to detect possible overdistension, and the pelvic floor muscles and the innervating nerves need to be checked for impaired recruitment and function. Besides, the surrounding connective and soft tissue of the pelvis and the birth canal need to be evaluated. Furthermore, it would be worthwhile to find a way to get more insight into the adaptation processes of fetus and birth canal. In a first step, simulation models could help to calculate the maternal bony and soft tissues, the different size relations of the fetus and birth canal, the adaptation processes of the these structures to the passing fetus, the adaptations of the fetus to the birth canal including its rotation, head flexion and head molding, and the different labor durations for the necessary adaptations.