Green’s Dictionary of Slang

poisoned adj.

pregnant.

1607		E. Sharpham Cupid’s Whirligig V vii: Was I not marryed yester day? ... like a young marryed woman that’s poisoned before shee is baud, I begin to long alreadie ... to be a bed with my husband.
c.1620		‘Excellent New Medley’ in Ebsworth Roxburghe Ballads (1871) I 14: Sure Meg is poyson’d for she swels.
1652		Laughing Mercury 8-16 Sept. 184: She [...] being stung very happily in a place that nothing endangered her life; some are of the judgement that she is poysoned; others that the sweling may go down again in a little time.
c.1698		B.E. Dict. Canting Crew n.p.: Poyson’d, Big with Child.
1725		New Canting Dict. [as cit. c.1698].
1737, 1759, 1760, 1776		Bailey Universal Etym. Eng. Dict. [as cit. c.1698].
1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue.
1811		Lex. Balatronicum.
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue.
1888–94		‘Walter’ My Secret Life (1966) I 121: Martha be poisoned [...] she be in the family way, we call it poisoned in these parts, when a girl ben’t married.
1983		R. Klein Jailhouse Jargon and Street Sl. [unpub. ms.].

In phrases

have a belly like a poisoned pup (v.)

to have a potruberant stomach.

1977

E. Torres Q&A 143: ‘Patrolman James Mullins, of the poisoned pup belly, late of the Twenty-third Precinct, a notorious thief and bagman’.