Miles O'Brien mentions not being able to witness Keiko give birth to Molly, an event which occurred in Disaster (1991). In that episode, O'Brien was stuck on the bridge of the Enterprise following a shipwide failure, and Keiko (along with Worf, who ultimately delivered Molly) was injured in Ten Forward, with no way for the two of them to communicate.
The production experimented with several different substances to depict the infant Changeling. They ended up using a few different mixtures, depending on what the scene called for, including a gelatin solution and a type of plastic called "hot melt vinyl."
Jadzia Dax does not appear in this episode. This is the first episode of the series in which she does not appear.
Quark says, "The center cannot hold", which is a line from the poem 'The Second Coming', by William Butler Yeats. The poem is essentially about the Apocalypse.