Abstract
Background: There is variation in the reported incidence of levator
avulsion (LA). Objective: Explore incidence of LA by mode of birth,
imaging modality, timing of diagnosis and laterality of avulsion. Search
strategy: We searched MEDLINE, EMBASE, CINAHL, AMED and MIDIRS with no
language restriction from inception to April 2019. Study eligibility
criteria: A study was included if LA was assessed by an imaging modality
after the first vaginal birth or if only delivered by caesarean section.
Case series and reports were not included. Data collection and analysis:
RevMan v5.3 was used for the meta-analyses and SW SAS and STATISTICA
packages for type and timing of imaging analyses. . Results: We included
37 primary non-randomized studies from 17 countries and involving 5594
women. Incidence of LA was 1%, 15%, 21%, 38.5% and 52% following
caesarean, spontaneous, vacuum, spatula and forceps births respectively,
with no differences by imaging modality. OR of LA following spontaneous
birth vs. caesarean was 10.69. While the OR for LA following vacuum and
forceps compared to the spontaneous birth were 1.66 and 6.32
respectively. LA was more likely to occur on the right side following
spontaneous birth (p = 0.02) and unilaterally vs. bilaterally following
spontaneous (P < .0001) and vacuum-assisted births (P =
0.0103) only. Incidence was higher if assessment was performed in the
first 4 weeks postpartum. Conclusions: Forceps significantly increases
incidence and severity of LA. Ultrasound and MRI are comparable
diagnostic tools but early postpartum imaging may lead to over diagnosis
of LA.