Impact of subsequent birth and delivery mode for women with previous OASIS: systematic review and meta-analysis

Obstetric anal sphincter injuries (OASIS) are serious complications of vaginal birth. In a pregnancy following OASIS women may be keen to avoid an elective caesarean section, yet cautious about pursuing another vaginal birth that may result in further damage to the pelvic floor and possible long-term anal incontinence. This review aimed to evaluate the impact of subsequent birth and its mode on anal incontinence (AI) and/or quality of life (QoL), for women with previous OASIS. Searches of MEDLINE, EMBASE, CINAHL, and AMED from inception to February 2016 were undertaken with selection criteria of any study evaluating the effect of a subsequent birth on AI and/or QoL in women with previous OASIS. Where possible, data were extracted to populate 2 x 2 tables and allow meta-analysis relating to the impact of subsequent birth on AI and/or QoL. Twenty-seven non-randomised studies were included. Meta-analysis of 14 studies (977 women) did not demonstrate any significant associations between AI in women with previous OASIS and subsequent birth or its mode. Impact on QoL was reported in 12 studies (912 women); however, difference in outcome reporting precluded data meta-analysis. Comparisons of outcomes and effective synthesis were limited by sample size, quality and heterogeneity of the studies included. Consequently, the optimal mode of delivery for women with previous OASIS is still not known and better data are needed.