Which assessment technique is contraindicated in diagnosing placenta previa?

The assessment technique that is contraindicated in diagnosing placenta previa is the pelvic examination. This is primarily due to the risk of causing bleeding or other complications. In cases of placenta previa, where the placenta is abnormally positioned over or near the cervical opening, performing a pelvic examination can potentially disrupt the placenta or provoke hemorrhage.

In contrast, ultrasound techniques, such as transabdominal and pelvic ultrasound, are safe and effective methods for assessing the condition of the placenta and determining its location in relation to the cervix. These imaging modalities allow for a non-invasive approach that does not involve manipulation of the cervix and minimizes the risk of complications. Fetal heart monitoring, while an important aspect of prenatal care, is not specifically used to diagnose placenta previa but rather to assess fetal well-being. Thus, a pelvic examination is the sole technique that poses a significant risk in this scenario, making it contraindicated for diagnosing placenta previa.