Case
Our case was a 36-year-old Asian women, gravida 2 para 0. Before 32
weeks of gestation, the patient had gone to the local clinical institute
as scheduled for prenatal examinations. Everything went smoothly during
her process of pregnancy by then. At 33 weeks of gestation, the patient
was found low lying placenta in that local institute by ultrasonography,
and was referred to our hospital, a municipal tertiary institute.
An ultrasonography Specialty Register gave the transabdominal ultrasonic
scan initially, and described as follows, “The placenta locates at the
anterior wall of the uterine cavity, the distance between the placenta
lower margin to the cervical internal os is 18mm. The insertion site of
the umbilical cord is at the posterior wall of the uterine cavity,
several vessels supported only by membranes insert into the placenta
edges, including one vessel goes along the interior surface of the
uterine fundus entering the placenta upper pole, and another vessel goes
along the lower uterine segment entering the placenta lower pole near
the cervix”(Figure.1 a ). Though a little puzzled as the
insertion site of the umbilical cord and the placenta location were at
posterior and anterior walls respectively, the diagnosis was obviously
vasa previa. According to the guidelines, we should accomplish the
cesarean section at 34 to 35 weeks[5].
However, the patient insisted on obstetricians’ reconsidering
possibility of vaginal delivery since the vessel entering the placenta
lower pole didn’t go exactly over the cervical internal os. 3 days
later, we offer second time of ultrasonic examination. This time, an
ultrasonography Consultant gave both transabdominal scan and
transvaginal gray scale with color Doppler, and described as follows,
“Yes, the umbilical cord insertion is at posterior wall and the
placenta locates at the anterior wall. But no obvious sign of vessel
overlying the cervix”. That result might overturn the previous
diagnosis of vasa previa. So should we still schedule the cesarean
section at 34 weeks of gestation?
In order to further understand the relationship between the patient’s
umbilical cord and placenta, we referred her to MRI scan. The
radiologists didn’t give any confirmation about umbilical vessels,
because they’re usually specialists focusing on diagnosis of placenta
increta, since vasa previa identification is commonly in sonographers’
field. But our obstetricians found a isolated vessel supported only by
membrane going along the lower uterine segment and entering placenta
lower pole near the cervix, just as the ultrasonography Specialty
Register had described(Figure.1 b and c ). The
umbilical cord truly inserted at posterior wall of the uterine cavity,
and Wharton’s jelly lost from there with a great number of isolated
vessels traveling through membranes connected to the anterior wall
placenta(Figure.1 c and d ).
At first, we considered there might be a very tiny placenta at the
posterior wall and then connected by naked vessels to the much larger
succenturiate lobe at the anterior wall. Immediately, an obstetric
Specialty Register pointed out there was hardly any space for placental
tissue existing between the amnion and the uterine muscle at posterior
wall. Ultimately, we got the conception that it was a special
“parachute” type of placenta, with no placental tissue at the
posterior wall, just several isolated vessels diverging from umbilical
posterior wall insertion site, like strings connecting to the parachute
canopy, to the anterior wall placenta.
We performed a cesarean section at 34 weeks and 3 days of gestation. At
the time of surgery, the incision at lower uterine segment was gradually
and carefully deepened until the decidua reached. Then rapidly cut
through the placenta that covered the lower anterior wall of the uterine
cavity, and got the fetus out immediately. A healthy female fetus was
delivered with Apgar scores 9,10 and birth weight 2450g. The placenta
was sequentially checked to confirm diagnosis of vasa previa on the spot
at delivery, and postoperatively by pathology gross examination(Figure.1e ) before pathological sectioning. The postoperative course of
the patient and the infant was uncomplicated and they were discharged 3
days later in a healthy condition.