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This is a plain English summary of an original research article. The views expressed are those of the author(s) and reviewer(s) at the time of publication.

Many women who have an assisted vaginal birth (using forceps or a vacuum cup) develop infections. A previous study (ANODE) showed that a single dose of preventive antibiotics protected women; this research led to a change in UK and WHO guidelines.

However, most women in the ANODE study had an episiotomy (surgical cut), so it was unclear if antibiotics also protected those with a tear of the perineum (the area between vagina and anus).

To address this uncertainty, researchers re-analysed the ANODE study data. They found that preventive antibiotics reduced infections after an assisted vaginal birth, irrespective of whether women had a perineal tear, an episiotomy, or both.

Women having an assisted birth were at greater risk of infection if antibiotics were delayed, if they had an episiotomy, a forceps birth, and/or were giving birth to their first child. Preventive antibiotics should be given as soon as possible to women who have an assisted vaginal birth, the researchers say.

More information on assisted vaginal birth is available on the NHS website.

The issue: who needs antibiotics after an assisted vaginal birth?

Assisted vaginal birth can use a vacuum cup (which fits on the baby’s head and applies suction) or forceps (tongs that are fitted carefully around the baby’s head). Both procedures are safe but increase the risk of infection. Just over 1 in 10 women with assisted vaginal births develop an infection.

The ANODE study, published in 2019, showed that preventive antibiotics (given before infection develops) reduce infections following an assisted vaginal birth. As a result, guidelines on the use of preventive antibiotics were updated (2021). They now recommend antibiotics after all assisted vaginal births.

However, most (almost 9 in 10) women in the ANODE study had an episiotomy. It was therefore unclear whether preventive antibiotics protect against infection in women with a tear.

The current study assessed whether preventive antibiotics reduced infections in all groups of women in the original ANODE study: those with a tear, an episiotomy, both, or neither. The researchers explored factors that could raise women's risk of infection and identified the best time to provide antibiotics.  

What’s new?

The ANODE study included women who received preventive antibiotics (amoxicillin and clavulanic acid) or a dummy drug (placebo) up to 6 hours after an assisted vaginal birth. In this new analysis, women were divided into groups according to their type of perineal injury. In total, 2144 (67%) women had an episiotomy, 277 (9%) a tear, 726 (23%) had both. Only 78 women (2%) had neither.

Researchers compared the number of confirmed or suspected infections within 6 weeks of birth. They included a new prescription of antibiotics for a wound-related infection, an infection of the vagina or urinary tract, or sepsis. They assessed the impact of the antibiotic’s timing.

They found that preventive antibiotics reduced infections compared with placebo among women with assisted vaginal births, whether they had a surgical cut, a tear, or both. Because so few women had neither a tear nor an episiotomy, the study could not assess whether antibiotics prevented infection for them.

The risk of infection was increased by:

  • a delay in giving antibiotics; women who waited more than 6 hours after giving birth were twice as likely to develop an infection compared to those who received antibiotics within 15 minutes (every additional 15 minute delay increased the risk of infection by 3%)
  • episiotomy (infection was almost 3 times more likely after episiotomy than after a perineal tear)
  • use of forceps (compared to vacuum cup)
  • first birth.

The analysis provided some evidence that women who were overweight are at increased risk of infection.

Why is this important?

The original ANODE study led to an update to international guidelines on the use of preventive antibiotics for assisted vaginal births, but it was unclear if they would be beneficial to women without an episiotomy. This new analysis shows that they protect against infection in women with an episiotomy and/or a tear, especially when given quickly.

The researchers call for guidelines to be updated. They recommend that women who have an assisted vaginal birth, and have a tear or episiotomy, should be given preventive antibiotics as soon as possible after giving birth.

What’s next?

The researchers recommend that clinicians advise women about infection risk factors (such as having a first birth, or being overweight) as well as symptoms and signs of infection. Women who may be at risk can take extra precautions to help prevent infection, such as keeping any wounds as clean as possible, and seek early help if they experience symptoms. Trying to become as healthy as possible before pregnancy, such as by losing weight, may also help prevent infections.

Vacuum birth was associated with less infection than forceps birth. The researchers say doctors could consider the increased risk of infection from forceps before performing an assisted vaginal birth. However, forceps will still need to be used in certain circumstances.

You may be interested to read

This summary is based on: Humphreys ABC, and others. Factors associated with infection after operative vaginal birth—a secondary analysis of a randomized controlled trial of prophylactic antibiotics for the prevention of infection following operative vaginal birth. American Journal of Obstetrics and Gynecology. 2022; 228: e1-e11.

Information on assisted vaginal births from the Royal College of Obstetricians and Gynaecologists.

The original ANODE study: Knight M, and others. Prophylactic antibiotics in the prevention of infection after operative vaginal delivery (ANODE): a multicentre randomised controlled trial. The Lancet. 2019; 393: 2395–2403.

World Health Organisation Guidelines on the use of preventative antibiotics for women undergoing assisted vaginal birth.

Funding: This study was supported by the NIHR Health and Technology Assessment Programme.

Conflicts of Interest: The authors declared no conflicts of interest.

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