LOOMS

Looms are the reproductive machines used by the Time Lords. They were invented by Rassilon after the Pythia cursed all Gallifreyans with infertility.

Some people think looms are not canon, and they are wrong. These people also tend to think that looms were introduced in Lungbarrow, despite Cat's Cradle: Time's Crucible mentioning them 55 books earlier.

If you want even more evidence of the canonicity of looms, they are mentioned in the 300% canon Faction Paradox series, though under the name 'Breeding Engines'.