What’s the suitable week for anomaly scan (20 week detail scan)

Hi, my wife have an appointment for the 20week scan but got diagnosed with covid the day before and was told we have to postpone our appointment. Would like to know if there is any timeline that we have to complete the anomaly scan or it can be done at a much later time as well? Example week 24 if she is recovered on week 23. Anyone reply will be appreciated.