Discussion
According to results of our study we suggested that fundal pressure at second stage of labour did not cause an increase in anal sphincter injury, contrary to expectations. Although the study designs are different, Cosner et al. stated that the second stage of labour was longer in the group in which fundal pressure was applied, and the incidence of third and fourth degree perineal lacerations was higher than the group without fundal pressure.15 Also our second stage of labour length was significantly longer in fundal pressure group. We know that Kristeller maneuver applied commonly in long lasting deliveries and difference in second stage of labour in our results is compatible with literature.16, 17 In another studies, fundal pressure is associated with shortened second stage and increased risk of severe perineal lacerations.18, 19 The inconsistency between our results and Cosner’s pilot study can be explained by uncertainty whether the accompanying episiotomy was median mediolateral and high rate (29.4%) of OASI in fundal pressure group.15 In others, it was not specified whether severe perineal injuries were OASI or third/fourth degree perineal tears.18, 19
Various methods have been investigated to reduce the risk of perineal tears during delivery. These methods include perineal massage, manual perineal support, warm compresses, limited use of episiotomy, and delayed straining. However the effect of mediolateral episiotomy on OASI in spontaneous vaginal deliveries is not clear. A recent meta-analysis concluded that mediolateral episiotomy can reduce OASI and should not be prevented, especially in nulliparous women.20 In an endoanal ultrasound study with 60 participants which evaluates impact of mediolateral episiotomy on incidence of obstetrical anal sphincter injury, authors suggested that mediolateral episiotomy does not seem to be protective against clinical or sonographic diagnosed OASIS even when episiotomy technique is considered.21 In studies comparing mediolateral episiotomy with medial episiotomy, it is clear that mediolateral episiotomy has a lower risk of obstetric injury compared to median episiotomy.20, 22 If an episiotomy is required, mediolateral episiotomy has been shown to be a protective intervention for OASI, especially in nulliparous women.23-25 Also the use of mediolateral episiotomy has a highly protective effect on the incidence of OASI during operative vaginal delivery.6 We thought that the application of liberal mediolateral episiotomy with over 45º from midline might have a protective effect on the anal sphincter in patients undergoing fundal pressure in our study.26
There are studies evaluating the effect of the Kristeller maneuver on the pelvic floor muscles rather than the studies evaluating the effect on the anal sphincter. Yousef et al., in their study on the effect of the Kristeller maneuver on pelvic floor muscles, showed that the application of fundal pressure in the second stage of labour was associated with more than twice the risk of levator ani muscle avulsion in women with a first vaginal delivery.27 In our recent study about pelvic floor damage and fundal pressure Fundal pressure during the second stage of delivery is associated with a higher risk of levator ani muscle defect and loss of anterior vaginal wall support.28 In these study, similar to our study, the duration of the second stage of labour was significantly longer in the fundal compression group, and episiotomy was performed more frequently in the fundal compression group.