Results
4 patients in the study group as the 1st, and 7th to 9th, had
inconclusive ultrasonic results for vasa previa at 23-25w of gestation,
and still had suspicious ultrasonography diagnoses at 31-33w since the
interpretation for vasa previa existence varied among ultrasonologists.
6 ones as the 2nd to 5th, 10th and 11th had no signs of vasa previa in
ultrasonic scanning at 23-25w, however, detected of naked previa vessels
once by a certain ultrasonologist at 31-33w, whilst another
ultrasonologist couldn’t confirm that in subsequent scanning. 2 patients
as the 6th and 12th, had been diagnosed by ultrasonography as vasa
previa at 23-25w, but previa vessels couldn’t be reconfirmed by
ultrasonography at 31-33w.
Maternal demographics, sonographic findings including placental
position, umbilical cord insertion and ultrasonographic judgement of
potential vasa previa for the study group are given in Table 1.
In the 12 patients enrolled into the study group with suspected vasa
previa but inconclusive ultrasonic results, MRI demonstrated vasa previa
in 11. The 12th patient had been excluded of vasa previa by MRI.
6 patients from 1st to 6th, had been identified as TypeⅠvasa previa in
MRI scanning. The 1st patient’s previa vessels just plastered to the
fetal scalp (Figure 1). Velamentous portion of the 2nd patient was tiny
and entering the lower pole of the low-lying placenta (Figure 2). 3rd
patient’s cord clearly diverged into velamentous form just before
entering placenta, and at the same level of fetal lips as the fetus was
facing down (Figure 3). From 4th to 6th patients, MRI also showed
mangrove umbilical vessels without Wharton’s jelly inserting placenta.
The 4th patient’s velamentous insertion was in a so large scale of
mangrove form, that almost like a parachute (Figure 4). In both 5th and
6th patients, fetal heads were so low that compressed the previa vessel
(Figure 5 & Figure 6).
The 7th patient was classified into Type Ⅱvasa previa. MRI clearly
displayed the mangrove bridge vessels connecting placental major and
succenturiate lobes, and one of the vessels overlying the cervix (Figure
7).
4 patients from 8th to 11th, were demonstrated as Type Ⅲ vasa previa by
MRI with boomerang vessels beyond the edges without placental mass
protection. The 8th patient’s previa boomerang vessels formed a
transverse V shape (Figure 8). Previa vessels in the 9th and 10th
patients were close to the uterine lateral walls (Figure 9 & Figure
10). In the 11th patient, the boomerang vessel was slightly compressed
by the fetal head (Figure 11).
MRI had excluded 12th patient of vasa previa diagnosis at 33 weeks of
gestation, as the mangrove bridge vessels connecting placental major and
succenturiate lobes, previously adjacent to the cervical internal
orifice, had moved away from the cervix a little laterally and upward,
because the lower uterine segment gradually formed and extended (Figure
12). And this phenomenon had been proved by pathology examination
showing naked mangrove vessels away from the amnion split.
MRI findings including placental position with morphology, vasa previa
types and directions, also pregnancy outcomes and pathology examinations
of the study group are summarized in Table 2.
In the control group, MRI had excluded vasa previa in all the 51
patients.
Placentas from the study and control groups were checked to confirm the
existences of vasa previa immediately at delivery, and postoperatively
by macroscopic examination before pathological sectioning. Pathology
examination showed no vasa previa was missed in MRI diagnosis, and all
the vasa previa running courses were coincided with directions displayed
in MRI.