Uterine fibroid is the commonest benign tumor of the uterus. It can be associated with difficulty to conceive. For those women who have uterine fibroid in pregnancy, it may cause pain due to degeneration, fetal malpresentation, or placenta previa. Most women with uterine fibroid may have undergone a myomectomy (surgical removal of the fibroid) prior to conception. The scar from myomectomy surgery may be associated with the uterine wall weakness and increases the risk of uterine rupture.
How common is uterine rupture after a myomectomy?
Uterine rupture is an obstetrical emergency that can be catastrophic for the mother and fetus. Previous uterine surgery, including previous cesarean delivery or myomectomy, is an established risk factor, although the exact magnitude of the associated risk remains uncertain.
The consequences of uterine rupture affect both the mother and the fetus. Maternal consequences of uterine rupture include severe internal bleeding (hypovolaemic shock), genitourinary injury, potential need for hysterectomy, and maternal death. The fetal sequelae include fetal hypoxia and fetal or neonatal death. In 2003, Chauhan (2003) estimated that the overall rate of hysterectomy secondary to uterine rupture is 0.09% with a perinatal mortality rate of 0.04% and a maternal mortality rate of 0.02%.
The reported prevalence of uterine rupture following a Caesarean section is about 1%. The frequency of uterine rupture is generally lower in developed countries compared undeveloped countries. Meanwhile, the incidence of uterine rupture following myomectomy is 0.79 %, which is comparable with that after cesarean section.
This risk is estimated to be lower than a classical Caesarean scar (incision on the muscular part of uterus). The American College of Obstetricians and Gynecologists (ACOG) has cited a uterine rupture risk of 4%-9% for women with prior classical caesarean and a trial of vaginal delivery is contraindicated.
The current available evidence shows no significant difference between the incidences of a rupture during pregnancy following a laparoscopic (1.2 %) versus an open myomectomy (0.4 %). The location, size of the fibroids and breach of the uterine cavity, surgical skills and technique (of suturing) also affect the likelihood of uterine rupture following previous myomectomy.
However, most studies on the safety of vaginal delivery after a myomectomy have several important limitations including non prospective, selection bias, under-reporting of iatrogenic complications and publication bias. The under-estimated true risk of uterine rupture, a potentially life-threatening event is possibly contributed by more primary Caesarean section performed to avert medicolegal litigation.
Should women with myomectomy have trial of vaginal delivery?
The mode of delivery following myomectomy is controversial. Though the risk for uterine rupture is low (less than 1%) following a myomectomy, regardless of the technique used, the evidence is not robust. It is clear that randomized studies are needed to study the effectiveness of laparoscopic myomectomy for the adverse outcome of uterine rupture before conclusive evidence can be used to present evidence-based recommendations for daily clinical practice.
This estimation of the incidence might be used for counseling women wishing to conceive after a myomectomy, but it should be done with utmost caution.
Some physicians will allow labor, as long as the uterine cavity has not been breached or less 50 percent of the uterine wall has been incised during myomectomy. However, ACOG currently recommends cesarean section following myomectomy be performed between 37 and 38 week to decrease the chance of the patient first going into labor with its risk of uterine rupture
Milton (2015) states that although there are limited data to support an elective Caesarean delivery, it should be offered to pregnant women who had myomectomies, in which large defects in the active segment of the uterus were created by removal of the fibroids. He feels that the total extent of the defect has a more significant impact on the risk of rupture compare to breach of the uterine cavity during the procedure.
There is currently insufficient evidence to determine the recommended mode of delivery following myomectomy. Some women are offered an elective Caesarean delivery by clinicians with the intention of reducing the risk of uterine rupture.
Uterine rupture during subsequent pregnancy seems to be a rare event. Due to paucity of robust evidence and given the potentially devastating consequences of uterine rupture, a scheduled delivery at 38 weeks should be offered to women with myomectomy. However, this does not preclude a trial of vaginal delivery after an informed decision.
- ACOG Practice Bulletin, 2004.
- Bernardi TS et al., Archives of Gynecology & Obstetrics. 2014
- Chauhan SP et al., American J Obstet Gyne 2003.
- Milton, SH. In: eMedicine, ME Rivlin (ed). 2015