Methods
In our institute, high-definition(HD) ultrasonographic scannings are routinely offered at 23-25 and 31-33 weeks of gestation to each registered pregnancy screening fetal congenital malformations and ultrasonographic soft markers. Vasa previa is also screened concomitantly. These three-dimensional trans-abdominal and trans-vaginal ultrasound examinations are performed using GE Voluson E8 Expert systems.
From January 2018 to December 2021, 12 patients with suspected vasa previa but inconclusive ultrasonography diagnoses at 23-25w or 31-33w were enrolled into the study group. 51 patients diagnosed by ultrasonography as mild ventriculomegaly with no vasa previa were enrolled into the control group. Both the study and the control groups had taken MRI scanning during the 3rd trimester, performed by GE Brivo MR355 system. MRI sequences included the following: (1) multiplanar T2WI single-shot fast spin echo(SSFSE), TR 2000ms, TE 68ms, matrix 288×256, gap 3 mm, slice interval 0, FOV 400×400mm; (2) T2WI fast spin echo(FSE), TR 8181ms, TE 85ms, matrix 320×224, gap 3 mm, slice interval 0, FOV 400×400mm; (3) T1WI Dual Echo Steady State(DESS), TR 180ms, TE 2.1ms, matrix 256×160, gap 3 mm, slice interval 0, FOV 400×400mm.
Placentas from all these enrolled patients were checked to confirm the existence of vasa previa immediately at delivery, and postoperatively by gross and microscopic pathology examinations. All the patients enrolled submitted written informed consent, and this study was approved by the Ethics Committee of the medical institute.