Birthday of but a single pang — Mother

Birthday of but a single pang 1
That there are less to come-
Afflictive is the Adjective
But affluent the doom-
(F.1541/J.1488)
[1] single:: only mother had suffered in a birthday. pang:: a brief keen spasm of pain which appears suddenly to pierce or shoot through the body or any part of it (OED 1); the pain of childbirth.
[2] less to come:: the pain of raising her child.
[3] Afflictive:: distressing, painful; trying, troublesome (OED), caused by the child. Adjective:: of the nature of an addition or adjunct (OED A), what comes along with the childbirth.
[4] affluent the doom:: a mother's destiny, the affluent ruin after birthday.