Keywords
uterine rupture - third trimester - spontaneous - fetal auscultation
Complete rupture of a pregnant uterus is a catastrophic obstetric event with a high
maternal and perinatal complication rate. Spontaneous uterine rupture in a nonlaboring
patient with an unscarred and congenitally normal uterus at the beginning of the third
trimester is exceedingly rare. We present a case of spontaneous third-trimester uterine
rupture with complete expulsion of the fetus and placenta into the abdomen that evolved
as the patient was observed.
Case Report
A 30-year-old G20010 presented at 2:40 am at 28 weeks' gestation complaining of intermittent periumbilical and mild epigastric
pain for 1 day. On arrival to our hospital, she had 10/10 right lower quadrant pain
aggravated by lying down. She denied abdominal trauma, chills, fever, nausea, anorexia,
vomiting, or vaginal bleeding. Her pregnancy to that point had been uneventful. A
previous second-trimester ultrasound had been reported as normal. Her physical examination
was normal other than tenderness to palpation in the right lower quadrant. Her cervix
was closed, thick, firm, and posterior. The fetal heart tracing was reassuring with
no signs of fetal compromise and no contractions were noted. The patient reported
a surgical history solely consisting of diagnostic laparoscopy for infertility and
endometriosis and an uncomplicated dilation and curettage for a previous early spontaneous
abortion. The initial working diagnosis was appendicitis versus ovarian torsion and
laboratories and imaging were ordered. A fetal ultrasound at 3:30 am showed a viable 29-week intrauterine pregnancy in the cephalic position with a possible
synechiae measuring 1.8 cm thick ([Fig. 1]). The placenta was posterior. The patient's coagulation studies including fibrinogen
returned normal and her hemoglobin was stable at 11.9 g/dL.
Fig. 1 First ultrasound on arrival. Arrow denotes the reported synechiae. Abbreviation:
FH, fetal head; LT, left.
Due to continued pain an abdominal-pelvic computed tomography (CT) scan with contrast
was performed at 4:57 am. After returning from radiology at 5:20 am, the fetus was found to have low heart tones in the 80s to 90s, and locating fetal
heart tones was difficult. A bedside ultrasound showed free fluid in the posterior
cul-de-sac and the radiologist who read the CT scan communicated with the attending
that the fetus was in the abdomen ([Fig. 2]). An emergency laparotomy was then performed at 05:47 am, which revealed both the placenta and fetus floating free outside of the uterus.
There was a uterine defect noted in the lower uterine segment anteriorly measuring
6 × 4 cm, which was closed.
Fig. 2 Computed tomography of the abdomen after the uterine rupture. Arrow denotes the empty
uterus. Abbreviation: F, fetus.
The female infant weighed 2 pounds 12 ounces and had an umbilical artery cord pH of
6.74 and a base deficit of 22.3. Apgar scores were noted to be 0 (1 minute), 4 (5
minutes), 6 (10 minutes), and 7 (15 minutes). Maternal estimated blood loss for the
entire case was 2 L. The patient then underwent an uncomplicated postoperative course
and was discharged home on postoperative day 4. The infant was discharged on day of
life 70 with a grade III intraventricular hemorrhage and seizures.
Discussion
The process of the dehiscence leading to the rupture probably began hours prior to
admission when she began having pain. In fact, on reviewing the first ultrasound image
it appears that the originally diagnosed synechiae was the edge of the uterine defect
and the fetal head was already extruded through the hole. Not only did the misdiagnosis
of the rupture lead to a delay, but labeling the uterine defect a synechiae gave the
obstetric team a reason for the abnormal image, delaying the diagnosis even more.
Uterine synechiae can follow uterine curettage, but they are not known to be a risk
factor for spontaneous obstetric uterine rupture unless they are treated surgically.[1] Also, the patient did have a history of uterine curettage and there is a reported
uterine perforation rate of 19.8 per 1,000 at the time of dilatation and curettage
when laparoscopy is used to evaluate the uterine fundus.[2] Because a perforation results in a scar and a scar is a risk for obstetric rupture,
it is conceivable she had a perforation even though her curettage was uncomplicated
and a uterine wall defect was not seen during her second-trimester ultrasound. Other
than the remote possibility of an unknown uterine scar from an unconfirmed perforation
at the time of curettage, she had no known risk factors for uterine rupture. Most
frequently, uterine rupture is related to prior cesarean section.[3]
[4] Regardless of the ultrasound report, the rupture was present and the diagnosis missed.
The report should always document that the fetus is in the uterus, and the presenting
part is within the lower uterus and/or birth canal. The maternal bladder should always
be visualized just above the presenting part.
This case illustrates the consequences of both diagnostic tunnel vision and the morbidity
of delay. Because the patient had no clear risk factors for uterine rupture and all
obstetric diagnostic elements were normal, the clinical team eliminated the possibility
of uterine dehiscence and impending rupture as the cause of the pain. Supporting the
decision to eliminate the most serious possible cause of the pain are the data suggesting
that the incidence of rupture of an unscarred uterus is estimated to be 1/8,000 to
1/15,000 deliveries.[5]
The poor condition of the newborn at birth illustrates the morbidity of delay. The
length of time of fetal oxygen deprivation is directly related to the baby's respiratory
and metabolic status,[6] and the decline in oxygen and buffer base occurs rapidly during acute, severe fetal
compromise.[7] This baby had severe hypoxic-induced metabolic acidemia that could have been avoided
if the fetal compromise were recognized earlier.[8]
The unfortunate coincidence of the rupture occurring at the time she was off of the
fetal monitor resulted in a significant delay in diagnosis and thus delivery.
The lessons learned from this case include a continued awareness of the possibility,
no matter how remote, of a potential impending uterine rupture when a pregnant woman
presents with persistent unexplained abdominal pain. The classic finding of an early
ruptured uterus is fetal compromise and diagnosing fetal compromise requires monitoring.
Intermittent fetal heart tone auscultation while the patient is off continuous monitoring
should have been performed and should be standard. Even with the misdiagnosis of the
rupture, intermittent auscultation could have resulted in the patient's immediate
return to triage.
In summary, there have been 35 reported cases of rupture of the primigravid uterus
in the literature in the past 60 years, 10 of which have been reported from the years
2000 to 2007.[9] This case represents the earliest known spontaneous rupture with a living newborn
in a patient with no known risk factors. The case is unique in that the rupture's
evolution was documented by “before-and-after” imaging and confirmed at laparotomy.
The case is instructive because it illustrates that a very simple and low-cost method
of monitoring, intermittent fetal heart tone auscultation with a doptone while she
was off continuous fetal monitoring, could have changed the condition of the newborn
at birth. Also, radiologists should note this condition as soon as the images show
up on their screen.
