catholic.com/thisrock/2002/0201fea5.asp
"What Is the Church’s Position?
The Congregation for the Doctrine of the Faith (CDF), having been approached for moral clarity concerning the latest biomedical technology and its intervention in the initial stages of human life, in 1987 issued the Instruction on Respect for Human Life in Its Origin and on the Dignity of Procreation (Donum Vitae) . This document is arguably the Catholic Church’s controlling statement on the dignity and respect due to the human embryo. Donum Vitae reaffirms the sacredness of human life “from the moment of conception,” meaning that the human embryo must be respected and treated as a person recognized to have, above all, the right to life. In addition, it must be defended in its integrity and tended and cared for, to the extent possible, in the same way as any other human being (DV 1:1).
In light of this teaching, can it be morally permissible to freeze or keep frozen a human being, even with the purpose of preserving his life?
The CDF’s answer is negative: “Freezing of embryos (cryopreservation) constitutes an offense against the respect due to human beings by exposing them to grave risks of death or harm to their physical integrity and depriving them, at least temporarily, of maternal shelter and gestation, thus placing them in a situation in which further offenses and manipulation are possible” (DV 1:6).
Equally clear, though tragic, is the statement that “in consequence of the fact that they have been produced in vitro, those embryos that are not transferred into the body of the mother and are called ‘spare’ are exposed to an absurd fate, with no possibility of their being offered safe means of survival which can be licitly pursued” (DV 1:5).
In other words, none of the options available for saving the life of these embryos can be said to be morally permissible and in conformity with the plan of God for human procreation. One might think that the issue would end there. But it has not. … "
Printed in Catholic Answers publication in 2002.
(Of course, some still dispute this teaching - they are in dissent.)