In vasa previa Type II, the velamentous vessels traverse the cervical os crossing between the lobes of a bilobed placenta. The most sensitive prenatal diagnostic modality for vasa previa is:

• A Transvaginal color Doppler in second trimester ✓
• B Transabdominal color Doppler at 16–18 weeks
• C MRI of the placenta at 28 weeks
• D Kleihauer-Betke test after vaginal bleeding

Explanation

Transvaginal color Doppler ultrasonography in the second trimester is the most sensitive method for prenatal diagnosis of vasa previa, identifying velamentous vessels crossing the internal os. Transabdominal Doppler is less sensitive due to fetal shadowing and maternal body habitus. MRI can diagnose vasa previa but is not the primary screening tool. The Kleihauer-Betke test detects fetal hemoglobin in maternal blood but is used after bleeding occurs, not for prenatal diagnosis. Prenatal diagnosis with planned cesarean delivery at 34–36 weeks dramatically reduces perinatal mortality from ~60% to <3%.

Reference: Williams Obstetrics, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.