Sharp or blunt trauma-assaults, accidents, bullets, knives
Congenital:
Before delivery:
Persistent, intense, spontaneous contractions Labor stimulation-oxytocin or prostaglandins Intraamnionic instillation-saline or prostaglandins Perforation by internal uterine pressure catheter External trauma-sharp or blunt
Uterine overdistention-hydramnios, multifetal pregnancy
During delivery:
Fetal anomaly distending lower segment Vigorous uterine pressure during delivery Difficult manual removal of placenta
Acquired:
Sacculation of entrapped retroverted uterus lower and women of great parity were numerous, primary uterine rupture predominated. As the incidence of cesarean delivery rose and especially as a subsequent trial oflabor in these women became prevalent through the 1990s, uterine rupture through the cesarean hysterotomy scar became the preeminent cause (Gibbins, 2015; Mone, 2016). However, concurrent with the diminished enthusiasm for a trial of labor in women with a prior cesarean delivery, incidence trends for the two types of rupture have again changed. In a study of 3942 cases of uterine rupture in more than 15 million women, approximately half were in women with a prior cesarean delivery (Yao, 2017). In 40 cases of rupture at Parkland Hospital from 2009 to 2016, 15 events (37 percent) were primary, and 25 (63 percent) were secondary (Happe, 2017).
Additional risks for rupture include other previous operations or manipulations that traumatize the myometrium. Examples are uterine curettage or perforation, endometrial ablation, myomectomy, or operative hysteroscopy (Kieser, 2002; Pelosi, 1997). In a study by Porreco and colleagues (2009), seven of21 women without a prior cesarean delivery had undergone prior uterine surgery.
In developed countries, the incidence of rupture is 1 in 4800 deliveries (Getahun, 2012). During a 40-year period in Norway, the uterine rupture rate rose significantly to about 1 in 1560 deliveries (Al-Zirqi, 2016). he frequency of primary rupture, however, approximates 1 in 10,000 to 15,000 births (Porreco, 2009). As discussed, one reason is a decreased incidence of women of great parity. Another is that excessive or inappropriate uterine stimulation with oxytocin-previously a frequent cause-has mostly disappeared. Maggio and associates (2014) found no association between the number of Montevideo units and secondary uterine rupture. In addition, in a recent analysis of three trials comparing high-versus low-dose oxytocin regimens, the rate of uterine rupture did not difer between groups (Budden, 2014). The rate of rupture is elevated with sequential induction of labor with prostaglandins and oxytocin (Al-Zirqi, 2017). At Parkland Hospital, we too have encountered primary uterine rupture in a disparate number of women in whom labor was induced with prostaglandin E1•
Blunt abdominal trauma can precipitate uterine rupture. Although the distended pregnant uterus is surprisingly resistant, pregnant women sustaining such trauma should be watched carefully for signs of a ruptured uterus (Chap. 47, p. 927). In one study of 13 cases of primary uterine rupture, trauma accounted for three cases (Miller, 1996). Other causes of traumatic rupture that are uncommon today are those due to internal podalic version and extraction, diicult forceps delivery, breech extraction, and unusual fetal enlargement such as with hydrocephaly.