During an ultrasound, sometimes the fetal sacrococcygeal region is not clearly visible. The vast majority of these cases are normal and do not mean that the fetus has malformations. The main reason why the sacrococcygeal region is not clearly visible is due to the inappropriate fetal position. If the fetus is in the supine position, the sacrococcygeal area is behind the fetus and it is difficult to detect this area through ultrasound. If the sacrococcygeal region is not clearly visible through ultrasound, you must stimulate the fetus properly during the next ultrasound, so that the fetus can move properly and try to see the sacrococcygeal region clearly.