No youth under 12 years of age shall be placed in detention except pursuant to judicial review and written findings describing why it is in the best interests of the youth to be placed in detention. Such review may be ex parte, and the youth does not need to be present. However, a juvenile court judge or referee must determine that the youth is eligible for detention under 419C.145 (Preadjudication detention) or 419C.156 (Detention of runaway from another state) and that appropriate alternative methods of controlling the youth's behavior are unavailable. A youth detained under this section shall have the right to a hearing as provided in 419C.153 (Detention review or release hearing)