shotgun wedding

Or shotgun marriage

noun

1. a wedding occasioned or precipitated by pregnancy.

2. Informal.,  a compromise, merger, accord, etc., occasioned by necessity.

   The coalition government was obviously a shotgun wedding.

shotgun wedding

noun

1. informal,  a wedding into which one or both partners are coerced, usually because the woman is pregnant

Word History and Origins

Origin of shotgun wedding¹

An Americanism dating back to 1925–30

Idioms and Phrases

An agreement or compromise made through necessity, as in Since neither side won a majority, the coalition government was obviously a shotgun wedding. This expression alludes to a marriage precipitated by a woman's pregnancy, causing her father to point a literal or figurative gun at the responsible man's head. Its figurative use dates from the mid-1900s.