Study finds lateral episiotomy lowers obstetric anal sphincter injury risk


A recent study finds that lateral episiotomy is a safe and effective procedure for reducing obstetric anal sphincter injuries in nulliparous women, highlighting its potential benefits during instrumental births.

Study finds lateral episiotomy lowers obstetric anal sphincter injury risk | Image Credit: © Summit Art Creations - © Summit Art Creations -

Study finds lateral episiotomy lowers obstetric anal sphincter injury risk | Image Credit: © Summit Art Creations - © Summit Art Creations -

Lateral episiotomy is a safe and effective procedure for reducing obstetric anal sphincter injury risk among nulliparous women, according to a recent study published in BMJ.


  1. A recent study published in BMJ found that lateral episiotomy significantly reduces the risk of obstetric anal sphincter injuries in nulliparous women undergoing vacuum extraction.
  2. Women who received lateral episiotomies had a 6% incidence of anal sphincter injuries compared to 14% in those who did not, with an adjusted risk ratio of 0.47.
  3. The study involved 702 nulliparous women from 8 hospitals in Sweden, randomly assigned to receive or not receive a lateral episiotomy during vacuum extraction.
  4. While the intervention group experienced more second-degree injuries, wound infections, and dehiscence, there were no significant differences in total self-referred or severe adverse events between the groups.
  5. Based on the findings, lateral episiotomy is recommended for nulliparous women needing vacuum extraction, with a call for further research on long-term patient-reported outcomes.

During vaginal birth, obstetric anal sphincter injury leads to anal incontinence and adversely impacts quality of life. Rates of obstetric anal sphincter injury range from 0.1% to 4% for spontaneous births and 6% to 24% for instrumental births.

The efficacy of an episiotomy for preventing obstetric anal sphincter injury remains unclear, with some studies indicated a potential increased risk. Other studies have reported no effect or the opposite effect. This has led to utilization of episiotomy varying significantly in instrumental births, from 17.1% in Denmark to 97.2% in Poland.

To evaluate the impact of episiotomy on anal sphincter injury risk across an adequately sized sample, investigators conducted a randomized controlled trial. From July 1, 2017, to February 15, 2023, 8 hospitals in Sweden participated in the analysis.

Participants included nulliparous women undergoing vacuum excision for a singleton, live, cephalic presenting fetus from 34 weeks’ gestation onward. Those with prior surgery for urinary or anal incontinence or genital prolapse were excluded from the study.

Attending physicians made the decision to perform vacuum excision independent of study participation. Afterward, 1:1 randomization was performed to determine whether patients would receive episiotomy.

All vacuum extraction procedures were performed based on clinical routine. The attending physician performed the extraction until the fetal head was crowning. At this point, the physician or midwife completed the lateral episiotomy, with standard practices used for injury examination, injury suturing, and postnatal care.

Daily assessments of perineal pain were performed sometime between 1 and 7 days after birth. Complications were identified through a questionnaire sent out 2 months after childbirth.

Obstetric anal sphincter injury was the primary outcome of the analysis, determined by third- or fourth-degree perineal injury of the external or internal anal sphincter muscles with surgical repair needed. This diagnosis was made by the attending physician based on Swedish guidelines.

Additional maternal outcomes included other vaginal or perineal injury, length of hospital stay, perineal pain, and birth experience. Neonatal outcomes included 5-minute Apgar score under 7, metabolic acidosis, neonatal intensive care unit admission, fetal fracture, scalp hematoma, shoulder dystocia, obstetric brachial plexus palsy, hypoxic ischemic encephalopathy, and neonatal seizures.

Postpartum hemorrhage and severe perineal pain were reported as safety outcomes. The Swedish pregnancy register was assessed for demographics, maternal and childbirth characteristics, and outcomes.

Severe adverse events were those leading to maternal death within 42 days postpartum or neonatal death within 28 days after birth. All adverse events were determined based on self-referral.

There were 344 women allocated to lateral episiotomy and 358 allocated to no episiotomy included in the analysis. Cesarean delivery following unsuccessful vacuum extraction was reported in 6% of those allocated to lateral episiotomy, vs 1% allocated to no episiotomy.

A risk difference of -7% was reported for obstetric anal sphincter injury between groups, at 6% in those allocated to lateral episiotomy vs 14% allocated to no episiotomy. The adjusted risk ratio was 0.47, with largely consistent findings reported across study sites and in sensitivity analyses.

In the per protocol population, the risk difference for obstetrical anal sphincter injury was -6.5%, at 6% for woman receiving lateral episiotomy and 13% receiving no episiotomy. Results for the total intention-to-treat population were consistent with those for the modified intention-to-treat and per protocol analyses.

Few cases of intact perineum were reported, and the intervention group had less first-degree injuries and more second-degree injuries than the comparison group. Wound infection and dehiscence were also significantly more common in the intervention group. However, differences were not observed for total self-referred adverse events or severe adverse events.

These results indicated a lateral episiotomy can be recommended in nulliparous women needing vacuum extraction. Investigators recommended more evidence be obtained about long-term patient reported outcomes.


Bergendahl S, Jonsson M, Hesselman S, et al. Lateral episiotomy or no episiotomy in vacuum assisted delivery in nulliparous women (EVA): multicentre, open label, randomised controlled trial. BMJ. 2024;385:e079014. doi:10.1136/bmj-2023-079014

Recent Videos
Addressing maternal health inequities: Insights from CDC's Wanda Barfield | Image Credit:
Addressing racial and ethnic disparities in brachial plexus birth Injury | Image Credit:
Innovations in prenatal care: Insights from ACOG 2024 | Image Credit:
The impact of smoking cessation on pregnancy outcomes | Image Credit:
Maximizing maternal health: The impact of exercise during pregnancy | Image Credit:
The importance of nipocalimab’s FTD against FNAIT | Image Credit:
Fertility treatment challenges for Muslim women during fasting holidays | Image Credit:
CDC estimates of maternal mortality found overestimated | Image Credit:
Study unveils maternal mortality tracking trends | Image Credit:
Related Content
© 2024 MJH Life Sciences

All rights reserved.