Progestogen only injectables

Injectables

Injected into the muscle or under the skin every 2 or 3 months, depending on product

How it works: 
Thickens cervical mucous to block sperm and egg from meeting and prevents ovulation
Effectiveness to prevent pregnancy: 
>99% with correct and consistent use. 97% as commonly used
Comments: 
Delayed return to fertility (about 1–4 months on the average) after use; irregular vaginal bleeding common, but not harmful