Ergometrine is commonly used for :
Obstetric indications of ergometrine (Ergonovine):

To control and prevent Postpartum hemorrhage. It is given at the time of delivery of the anterior shoulder.
After Caesarean Section/instrumental delivery - to prevent uterine atony.
To ensure normal involution in multipara.
PostPartum Hemorrhage
To shorten  2nd stage of labour
Dysmenorrhea
Toxemia of pregnancy