This chapter describes procedural prerequisites. After relevant counseling and obtaining informed, written consent, pregnancy is evaluated to decide the time, method and route of approach for the invasive prenatal diagnosis test. This chapter covers the pregnancy evaluation and clinical evaluation. The most important of ultrasound evaluation is the orientation of the entire procedure. One can visualize, orienting for the entire journey of the needle or cannula towards the target for procedure of biopsy. Ultrasound evaluation helps to decide the route of approach, the length of the needle or cannula and also helps to preform and shape the malleable cannula as for the transcervical procedures.