How long does it take to get results from amniocentesis? Amniocentesis is a preoperative diagnostic technique commonly used to detect the presence of chromosomal abnormalities and congenital defects in the fetus. Amniocentesis takes time to diagnose, so how long does it take to get results from amniocentesis? Several aspects will be elaborated below. 1. Preparation before amniocentesis. Before amniocentesis, the doctor will explain the risks and contraindications of the procedure to the pregnant woman, and conduct relevant examinations, such as blood tests of the pregnant woman.