Grand Rounds

What is The Success Rate of Trial of Labor After a Previous Failed Vacuum-Assisted Vaginal Delivery?

BACKGROUND AND PURPOSE:

Trial of labor after cesarean delivery (TOLAC) has a success rate between 60% to 80%
- Data limited on success following previous failed assisted vaginal delivery
Levin et al. (Obstetrics & Gynecology, 2019) assessed TOLAC success rates among women with a previous failed vacuum-assisted vaginal delivery

Retrospective cohort study (2008-2017)
Participants: All women who underwent cesarean delivery following a failed vacuum
Characteristics of women who underwent subsequent TOLAC vs elective cesarean as well as outcomes were compared

166 women were included
- Median interdelivery interval: 28 months
- TOLAC: 68% | Elective repeat cesarean: 32%
- There were some small statistical differences between TOLAC and repeat cesarean groups, but were not considered clinically significant (e.g., median gestational age was lower among repeat cesarean group [38w0d] vs TOLAC group [39w3d])
TOLAC success rate: 67% | 30% of this group were delivered using vacuum | Failed vacuum rate was 26% in the group that underwent TOLAC
Newborn outcomes
- 1-minute Apgar score <7 was lower in the failed vs successful TOLAC group: 16% vs 3%
  - Odds ratio (OR) 7.16 (95% CI, 1.36 to 37.45; P=0.01)
- 5-minute Apgar score <8 was lower in the failed vs successful TOLAC group: 8% vs 0%
  - OR 15.5 (95% CI 1.78 to 308.7; P=0.03)
- No difference in birthweight was seen between groups
Maternal adverse events
- No obstetric anal sphincter injury, postpartum hemorrhage or uterine rupture were reported in TOLAC group

TOLAC following failed vacuum-assisted delivery was “associated with an acceptable success rate (67%)”
The authors go on to state that these results could provide reassurance to women who do choose to undergo TOLAC following a failed vacuum delivery
Prospective trials would provide higher quality evidence, but such studies “would prove challenging”

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