First-time mothers needing medical assistance during childbirth can significantly reduce their risk of obstetric anal sphincter injury (OASI) with a lateral episiotomy, according to a new study. This type of incision, made at an angle in the tissue between the vaginal and anal opening, can more than halve the chance of this serious perineal trauma.
Researchers from Stockholm's Danderyd Hospital and Karolinska Institutet conducted a randomized clinical trial, with their findings published in The BMJ. OASI affects the anal sphincter muscles and can result in anal incontinence and difficulty controlling gas and excrement. It can also decrease quality of life and cause sexual problems. In Sweden, around 5% of first-time vaginal births result in this severe perineal damage.
"Women giving birth for the first time and requiring instrumental birth are at the highest risk of sustaining OASI," explained Sophia Brismar Wendel, associate professor in obstetrics and gynecology at the Department of Clinical Sciences, Danderyd Hospital, Karolinska Institutet, and senior consultant at the Department of Women's Health, Danderyd Hospital. "Therefore, we wanted to assess if such injury could be prevented in this group with a lateral episiotomy when the baby's head is crowning."
The EVA (Episiotomy in Vacuum Assisted delivery) trial recruited participants from eight Swedish hospitals between 2017 and 2023. Over 6,100 pregnant women expecting their first child agreed to participate if vacuum assistance was needed during delivery. A total of 702 women with vacuum-assisted deliveries were randomly assigned to receive a lateral episiotomy or no episiotomy.
The study found that lateral episiotomy reduced the risk of OASI by an average of 53 per cent. Among those who received the procedure, 6.1 per cent sustained an OASI, compared to 13.1 per cent in the non-episiotomy group. Additionally, the procedure did not increase the risk of severe blood loss, negative birth experience, prolonged hospitalization, or additional complications. However, there was an increased risk of wound complications, such as infection and wound dehiscence, in the episiotomy group.
"Episiotomy as a medical intervention is controversial as it has historically also been used for normal births, sometimes without the woman's consent," said Sophia Brismar Wendel. "The use of episiotomy is highly variable in different countries, and in Sweden we've practiced restrictive use given the lack of evidence. However, these results may impact obstetric care both in Sweden and elsewhere."
The trial is also collecting data on the women's self-reported symptoms at one and five years after childbirth. The results from the one-year follow-up will soon be analyzed, which might provide insights into differences in symptoms such as anal incontinence and sexual function.
"This may help doctors and pregnant women in shared informed decision-making regarding the use of a prophylactic lateral episiotomy," added Sophia Brismar Wendel.
