Vaginal delivery is considered to be the most eminent predisposing factor for prolapse as a result of levator muscle insult, which has serious consequences on pelvic organ support and is strongly associated with pelvic organ prolapse .
Magnetic resonance imaging (MRI) of the pelvic floor has become an increasingly utilized method for pelvic floor weakness assessment and pelvic organ prolapse. It allows assessment of all the compartments at rest and strain within a single examination. In addition, MRI allows assessment of the muscular and ligamentous anatomy of the pelvic floor as well as potential other incidental findings that may contribute to the symptoms. Moreover, MRI is less invasive, does not entail any ionizing radiation, and is less dependent on operators .
In the dynamic scans, we studied changes in all three compartments of the pelvic floor as pelvic floor dysfunction is almost always multi-compartmental even if the presentation was unicompartmental.
Among the studied cases, we found that 3.85% of cases have mono-compartment affection, 23% bi-compartments affection, and 73% had multi-compartmental affection; accordingly, the majority of cases have multi-compartmental affection.
As for the anterior compartment, 73.1% of the case group had bladder neck descent and 50% had cystoceles, while in the middle compartment, 92.3% of the cases had cervical descent “vaginal vault” descent in hysterectomy. In the posterior compartment, 92.3% of cases had rectal prolapse and 73.1% had rectocele.
The above findings are in concordance with Bitti et al.  and Law et al.  who reported that female patients presenting with symptoms of unicompartmental affection often have generalized damage of their pelvic floor as a whole with increased incidence of recurrence following repair of the symptomatic compartment only.
This is also in agreement with Woodfield et al.  who reported the superiority of MRI having the capability to assess the pelvic floor support structures as well as simultaneously scanning all pelvic compartments in order to detect pelvic organ prolapse in any compartment as usually more than one compartment is affected.
In this study, there was a significant difference between case and control groups in pelvic floor muscle thickness with P value ≤ 0.001 for right and left puborectalis muscles and P value 0.05 and 0.03 for left ilicoccygeus and puborectalis midpoint thickness, respectively, with 46.2% of the case group having puborectalis muscle injury and 11.5% having iliococcygeus muscle injury. The correlation between vaginal delivery and muscle thickness revealed a significant difference in the right and left puborectalis muscle thickness in multi-gravida with P value = 0.014 and 0.01.
This agrees with Leijonhufvud et al.  who reported increased rates of surgeries for stress urinary incontinence and pelvic organ prolapse surgery with increased number of vaginal deliveries.
Also agreeing with Bitti et al.  who stated that the puborectalis muscle is often injured during vaginal delivery, the injuries can be in the form of tear, thinning, bowing, and atrophy following pudendal nerve affection.
Similarly, Naganawa et al.  stated that there is a directly proportionate relation between the number of vaginal deliveries and downward displacement of the rectum; there were significant differences in the distance from the rectum descent to PCL between the nulliparous and multipara groups (p < 0.01).
Those results are coinciding with those stated by Yan et al.  who studied 80 women 45–60 days postpartum showing a prevalence of puborectalis injuries in 13.75%. They also emphasized the importance of postpartum MRI examination to rule out associated iliococcygeus muscle injuries or thinning that can be missed by ultrasound examination. These results also agreed with Alt et al.  detecting numerous superficial and deep pelvic morphological changes between nulliparous and primiparous female (P < 0.001).
DeLancey et al.  disagree with these results as they studied the integrity and bulk of puborectalis muscle by MRI following vaginal delivery and stated that it was visible in its expected location with no evidence of muscle avulsion from its pubic attachment.
In this study, we detected that puborectalis muscle thickness decrease with age with p values 0.004, 0.01 and 0.03 for the right puborectalis, the left puborectalis and puborectalis mid point thickness respectively while iliococcygeus muscles showed no significant difference.
This agrees with Alperin et al.  who discovered that the thickness of all pelvic floor muscles was siginificantly decreased with aging (P < 0.05).
Also, Rahmanou et al.  stated that there is a noteworthy correlation found between the increased age of the primigravida mother and the risk of pelvic floor injury with evidence of at least one form of major pelvic floor trauma (P = 0.003) as well as levator avulsion in (18.7%), micro-trauma in (12.8%), and obstetric anal sphincter injuries in (24.4%).
This was consistent with the previous researches done by Bozkurt et al.  who stated that the incidence of pelvic floor dysfunction rises markedly with age nearly 10% of women with age range 20 to 39 years, in comparison with 50% of females aged ≥ 80 years suffer from at least one pelvic floor dysfunction disorders, with higher prevalence in multiparous females compared with nulliparous females, thus emphasizing the role of obstetric trauma.
In this study, the relation between pelvic floor descent and both PR and IL muscle thickness without tears as well as muscle defects was insignificant with P value ≥ 0.05; that was agreeing with Dietz HP et al.  whose study was designed to quantify the role of a direct childbirth trauma to the insertion of the puborectalis muscle, on the inferior pubic ramus. Such trauma is common and clearly linked to vaginal delivery; their results stated pelvic organ prolapse was seen in 150/181 (83%) women with puborectalis defects and in 265/600 (44%) women without puborectalis defects (P < 0.0001).