Linked from
The 12 pages that link to Embryonic diapause, each with the reason it gives.
OviparityRelated: Some eggs delay development until environmental conditions improve.
PlacentaliaRelated: Some placentals use diapause to time pregnancy with favorable conditions.
KillifishRelated: Annual killifish embryos can pause development in soil while their pools are dry.
CyprinodontiformesRelated: Several annual killifishes use diapause to outlast drought.