Postoperative Uterine Rupture Causes
The primary cause of postoperative uterine rupture is previous cesarean section, with risk increasing dramatically with each additional cesarean delivery, particularly when combined with trial of labor. 1
Primary Risk Factors
Previous Cesarean Section (Most Important)
The dominant cause of postoperative uterine rupture is uterine scarring from prior cesarean delivery. The risk escalates exponentially with the number of previous cesarean sections:
- One prior cesarean: 22 per 10,000 births (0.22%)
- With labor after cesarean: 35 per 10,000 births (0.35%)
- Vaginal birth after cesarean (VBAC) attempt: 87 per 10,000 (0.87%)
- Planned repeat cesarean: 9 per 10,000 (0.09%) 1
The type of uterine incision matters critically. Classical cesarean scars (vertical incision in the contractile upper uterine segment) carry the highest rupture risk and are considered a contraindication to trial of labor 2, 3.
Other Uterine Surgeries
Beyond cesarean delivery, any surgical trauma to the uterine wall creates rupture risk:
- Laparoscopic myomectomy: Accounts for 76% of non-cesarean scar ruptures in recent series 4
- Hysteroscopic myomectomy: 8% of non-cesarean ruptures 4
- Laparoscopic cornual resection (for ectopic pregnancy): 16% of non-cesarean ruptures 4
- Deep infiltrating endometriosis surgery: Particularly retrocervical procedures using monopolar energy 5
- Uterine curettage (repeated): Multiple curettages weaken the myometrium and increase rupture risk 6, 7
- Manual removal of placenta
- Myomectomy (open or laparoscopic) 3, 6
Critical distinction: Non-cesarean scar ruptures result in more severe bleeding (>1500 mL) requiring transfusion compared to cesarean scar ruptures 4.
Secondary Contributing Factors
Obstetric Interventions
Labor induction agents (in scarred uterus):
Improper oxytocin use (excessive dosing or prolonged administration) 6
Obstructed labor (though less common in modern practice) 6
Uterine Pathology
- Placenta accreta spectrum: Increases risk of wall disruption, particularly at scar sites 8
- Uterine malformations: Bicornuate uterus, septate uterus 9, 6
- Adenomyosis and submucous fibroids 10
- Cesarean scar defect/niche: 24-88% prevalence after cesarean, may evolve into rupture site 1
Iatrogenic Trauma
- Operative hysteroscopy: Even without recognized perforation at the time of procedure 9
- Uterine perforation (from IUD insertion or curettage) 9
- Assisted delivery trauma (forceps, vacuum) 6
High-Risk Clinical Scenarios
Inter-delivery interval <18 months after cesarean increases rupture risk and should trigger heightened surveillance 2.
Multiple prior cesarean sections (≥3) create a cumulative weakening effect, with some women losing the option for vaginal delivery entirely 2.
History of uterine perforation (even if repaired) from any cause—IUD, curettage, or surgical procedure—creates a permanent weak point 9, 7.
Common Pitfalls
Underestimating laparoscopic surgery risk: Laparoscopic myomectomy now represents the majority of non-cesarean ruptures, yet patients often aren't counseled about pregnancy risks 4
Assuming hysteroscopy is "safe": Even diagnostic or minor operative hysteroscopy without recognized perforation can lead to rupture 9
Missing the significance of multiple curettages: Repeated endometrial instrumentation cumulatively weakens the myometrium 7
Using misoprostol in any scarred uterus: The 13% rupture rate makes this absolutely contraindicated 2
Inadequate assessment of posterior uterine wall: Most attention focuses on anterior scars, but posterior wall surgery (endometriosis, posterior myomectomy) also creates rupture risk 5