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Interventions to prevent Obstetric anal sphincter injuries (third and fourth degree perineal tears)

Risk factors for OASIS often become apparent late in labour and the degree to which these factors can potentially be modified during labour is yet to be determined. However, some methods of performing the delivery may show evidence of protection.

1.    Head Control:  

  • In women having a spontaneous vaginal delivery, the rate of obstetrical anal sphincter injury is decreased when the obstetrical care provider slows the fetal head at crowning (SOGC, 2015).

2.    Episiotomy:

  • At the time of either a spontaneous vaginal or instrumental delivery, the obstetrical care provider should follow a policy of "restricted" episiotomy (i.e., only if indicated), rather than "liberal" use (i.e. routine), for the prevention of obstetrical anal sphincter injuries (SOGC, 2015).
  • If an episiotomy is deemed indicated, preference for a mediolateral over a midline should be considered.The optimal cutting angle appears to be no less than 45 degrees, ideally around 60 degrees (SOGC, 2015).

3.    Perineal Support:

  • Use warm compresses to prevent perineal tears (Aasheim et al, 2017)
  • Use antenatal perineal massage (Aasheim et al, 2017; Beckmann et al, 2013)

Prevention of Uterine Rupture:  Guidelines for Vaginal Birth After previous Caesarean Birth (SOGC, 2018)

  1. Provided there are no contraindications, a woman with one previous transverse low-segment Caesarean section should be offered a trial of labour (TOL) with appropriate discussion of maternal and perinatal risks and benefits. The process of informed consent with appropriate documentation should be an important part of the birth plan in a woman with a previous Caesarean section (II-2B).
  2. The intention of a woman undergoing a TOL after Caesarean section should be clearly stated, and documentation of the previous uterine scar should be clearly marked on the prenatal record (II-2B).
  3. For a safe labour after Caesarean section, a woman should deliver in a hospital where a timely Caesarean section is available. The woman and her healthcare provider must be aware of the hospital resources and the availability of obstetric, anesthetic, pediatric, and operating-room staff (II-2A).
  4. Each hospital should have a written policy in place regarding the notification and (or) consultation for the physicians responsible for a possible timely Caesarean section (III-B).
  5. In the case of a TOL after caesarean, an urgent laparotomy should be set-up immediately to facilitate delivery as quickly as possible (III-C).
  6. Continuous electronic fetal monitoring of women attempting a TOL after Caesarean section is recommended (II-2A).
  7. Suspected uterine rupture requires urgent attention and expedited laparotomy to attempt to decrease maternal and perinatal morbidity and mortality (II-2A).
  8. Oxytocin augmentation is not contraindicated in women undergoing a TOL after Caesarean section (II-2A).
  9. Medical induction of labour with oxytocin may be associated with an increased risk of uterine rupture and should be used carefully after appropriate counselling (II-2B).
  10. Medical induction of labour with prostaglandin E2 (dinoprostone) is associated with an increased risk of uterine rupture and should not be used except in rare circumstances and after appropriate counselling (II-2B).
  11. Prostaglandin E1 (misoprostol) is associated with a high risk of uterine rupture and should not be used as part of a TOL after Caesarean section (II-2A).
  12. A Foley catheter may be safely used to ripen the cervix in a woman planning a TOL after Caesarean section (II-2A).
  13. The available data suggest that a trial of labour in women with more than one previous Caesarean section is likely to be successful but is associated with a higher risk of uterine rupture (II-2B)
  14. .Multiple gestation is not a contraindication to TOL after Caesarean section (II-2B).
  15. Diabetes mellitus is not a contraindication to TOL after Caesarean section (II-2B).
  16. Suspected fetal macrosomia is not a contraindication to TOL after Caesarean section (II-2B).
  17. Women delivering within 18 months of a Caesarean section should be counselled about an increased risk of uterine rupture in labour (II-2B).
  18. Postdatism is not a contraindication to a TOL after Caesarean section (II-2B).
  19. Every effort should be made to obtain the previous Caesarean section operative report to determine the type of uterine incision used. In situations where the scar is unknown, information concerning the circumstances of the previous delivery is helpful in determining the likelihood of a low transverse incision. If the likelihood of a lower transverse incision is high, a TOL after Caesarean section can be offered (II-2B).

Vaginal Birth after Previous Low-Segment Caesarean Section:  Recommendations from Association of Ontario Midwives (VBAC CPG Working Group, 2011)

  1. The risks and benefits of VBAC compared with ERCS should be discussed with women who have a history of CS. This discussion, including the woman's decision, should be appropriately documented in the woman's chart.
  2. Recommend planned VBAC as a means to achieve the benefits of normal childbirth, while being sensitive to each woman's concerns and values and respecting her informed decision.
  3. Recommend planned VBAC for women intending to have more than one child after the previous CS. Increased maternal and perinatal morbidity associated with ERCS and multiple CS has long-term health implications. 

Recommendations 1-3 presuppose an absence of contraindications to vaginal birth/VBAC.

  1. Midwives should discuss the relevant factors which may influence the likelihood of success or risk of VBAC with their clients. Inform clients that such factors are not contraindications to VBAC but may be considerations in their care during labour. 
  2. In developing the plan for care of a woman planning a VBAC, request and review a copy of the operative record from the previous caesarean section(s). Inability to obtain the previous record should be documented in the woman's chart.
  3. For women planning VBAC, induction of labour should be avoided unless the benefits outweigh the risks. When necessary, midwives should consult obstetrics and review the risks and benefits of methods of induction with the woman and the consultant. As with any clinical situation in which midwives manage care, a clear plan for ongoing communication with the consultant about progress in labour and maternal and fetal well-being is recommended when midwives are primary care providers for induction of VBAC labour.
  4. When augmentation or induction of labour is required during a VBAC labour and the midwife is the primary care provider, the midwife should take into account how quickly the obstetrical and pediatric team will be available in the event that emergency assistance is required. This may include ongoing communication with the team about progress in labour and maternal and fetal well-being.
  5. Fetal heart monitoring may occur by:
    1. intermittent auscultation q 15 minutes in active labour and q 5 minutes in the second stage; or
    2. using continuous EFM per current protocols.
  6. The relative and absolute risks of severe adverse events in the absence of continuous electronic fetal monitoring are unknown. 
  7. Continuous EFM should be used if labour is prolonged or if any fetal heart rate abnormalities are noted with intermittent auscultation.
  8. For women with a prior history of CS it is important for midwives to diagnose and document the onset of active labour accurately and to be vigilant for prolonged labour.
  9. For women with a prior history of CS in whom prolonged labour has been identified, obstetric consultation should be requested and IV access and continuous EFM monitoring should be initiated, if not already in place, while awaiting obstetric consultation.
  10. Prompt consultation should be initiated if the woman labouring after a previous CS experiences any unusual pain or if epidural anaesthesia is being used and is not effective.
  11. An informed choice discussion regarding the risks and benefits of VBAC and choice of birth place should be comprehensive and well documented. Documentation of this discussion should include: an outline of risks and benefits discussed, the woman's values and preferences, and any recommendations made by the midwife, if applicable.
  12. Women should be informed that there is little published evidence on the outcomes, including safety, of VBAC in the out-of-hospital setting. While the quality of these studies varies, they do not demonstrate increased risk.
  13. For clients planning VBAC, describe the VBAC policies in place at the hospital(s) where the attending midwives have hospital privileges. Women's informed choices to accept or decline recommended interventions in hospital should be respected.
  14. For women who have undergone a CS, discuss the association between delivery interval and risk of uterine rupture and considerations for family planning prior to discharge from midwifery care.

Conduct Clinical and System Reviews

Given the broad range of potential causes of complications from obstetric trauma, in addition to the recommendations listed above, we recommend conducting clinical and system reviews to identify latent causes and determine appropriate recommendations.

If your review reveals that the healthcare facility's obstetric trauma cases are linked to specific processes or procedures, you may find guidelines related to the specific procedure here:

Clinical and System Reviews, Incident Analyses

Occurrences of harm are often complex with many contributing factors. Organizations need to:

  1. Measure and monitor the types and frequency of these occurrences.
  2. Use appropriate analytical methods to understand the contributing factors.
  3. Identify and implement solutions or interventions that are designed to prevent recurrence and reduce risk of harm.
  4. Have mechanisms in place to mitigate consequences of harm when it occurs.

To develop a more in-depth understanding of the care delivered to patients, chart audits, incident analyses and prospective analyses can be helpful in identifying quality improvement opportunities. Links to key resources for analysis methods are included in Resources for Conducting Incident and/or Prospective Analyses section of the Introduction to the Hospital Harm Improvement Resource.

Chart audits are recommended as a means to develop a more in-depth understanding of the care delivered to patients identified by the Hospital Harm measure. Chart audits help identify quality improvement opportunities.

Useful resources for conducting clinical and system reviews: