The pills are sold in sealed blister packages containing 21 active pink pills and 7 inactive white pills.
"Active pills that are chipped may contain less of the active drug ingredients, which may reduce Alysena's effectiveness in preventing pregnancy," Health Canada said in a statement.
The affected lot is Alysena 28 (DIN 02387875), lot LF10133A, expiry date 10/2019.
Consumers are advised:
Do not consume a pill if it looks unusual (for example, it is chipped, has jagged edges or is broken). Examine both sides of each pill thoroughly before taking it. It may not be immediately obvious from looking at the blister package that there is a problem with the pills, since the underside of the pill cannot be seen while in the blister pack.
If you have a package with an unusual-looking pill, return it to your pharmacy for a replacement package.
Do not stop taking your birth control pills as this may result in pregnancy. Talk to a health care professional if you have questions or concerns about your birth control product, including about missed doses and alternatives.