Green’s Dictionary of Slang

(US) a premature baby; also attrib.

1927		D. Barkley ‘Hospital Talk’ AS II:7 314/1: A baby delivered prematurely is a ‘premy’.
1942		Berrey & Van den Bark Amer. Thes. Sl.
1970		J. Wambaugh New Centurions 254: ‘She got a new baby, one of them preemeys, jist a tiny bug of a chil’.
1985		J. Briskin Too Much Too Soon (1986) 700: We’re in New Guinea [...] better to be a preemie in Washington than at the Tasi.
1993		(con. 1969) N.L. Russell Suicide Charlie 180: There was lost weight to be regained and progress to be monitored, but he was a large baby as premies go, and healthy once his lungs started to work.
2005		advert 🌐 Parent of a Preemie? Share your story and provide online help to other families.
2017		T. Spicer Good Girl Stripped Bare 182: ‘I guess you’ll be looking after a premmie baby in a couple of weeks’.