Gin

There are three possible reasons for this description:

1. Gin has often been considered an abortifacent, hence the ruination of motherhood.
2. Gin was also a cheap intoxicant, used in seduction for many years -- "ruining" girls and turning them into mothers.
3. Gin was the refuge of the working classes, and many suffered from alcoholism, during the Regency and Victorian periods of British history, making women unfit for their role as mothers.