This patient is experiencing vaginal bleeding in the third trimester. Performing a digital pelvic examination for vaginal bleeding in the latter half of pregnancy without first ruling out placenta previa is contraindicated.1 During digital examination, the finger comes in direct contact with the placenta, which can cause catastrophic hemorrhage.1,2 A transvaginal or transabdominal ultrasound should be obtained when a patient presents with vaginal bleeding in the second or third trimester of pregnancy, as in this case. Transvaginal ultrasonography is preferred over transabdominal ultrasonography for diagnosing placenta previa because it is more accurate in identifying the placenta overlying the internal os.1 During a transvaginal ultrasound, the transvaginal probe is placed in the vagina against the anterior fornix at an angle 2 to 3 cm away from the internal os, which prevents it from slipping into the cervical canal and coming into contact with the placenta. Thus, the placenta can be visualized without inadvertently causing hemorrhage.1,2 The image quality of a transabdominal ultrasound is poorer compared with a transvaginal ultrasound because the transabdominal probe is placed farther away from the placenta. Also, the fetal head may obscure the placental edges when transabdominal ultrasound is performed in the second or third trimester, resulting in a higher rate of false-positive diagnoses of placenta previa.1,2
- Digital pelvic examination.
1. Oyelese Y, Smulian JC. Placenta previa, placenta accreta, and vasa previa. Obstet Gynecol 2006;107:927–41.
2. Farine D, Fox HE, Jakobson S, Timor-Tritsch IE. Vaginal ultrasound for diagnosis of placenta previa. Am J Obstet Gynecol 1988;159:566–9.
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