Jamieson, Fausset and Brown on Genesis 30:20

20. And Leah said, God hath endued me with a good dowry--The birth of a son is hailed with demonstrations of joy, and the possession of several sons confers upon the mother an honor and respectability proportioned to their number. The husband attaches a similar importance to the possession, and it forms a bond of union which renders it impossible for him ever to forsake or to be cold to a wife who has borne him sons. This explains the happy anticipations Leah founded on the possession of her six sons.