Health Canada announced the voluntary recall of oral contraceptives made by Mylan Pharmaceuticals.
The packages normally contain three rows of active pills that are white and one row of placebo pills in green.
"Missing one or more active (white) pills could result in reduced effectiveness for contraception, with the possibility of an unplanned pregnancy," the department said late Tuesday.
The affected product is Freya-28 in these lots: 3739F001B and 3739F002B.
The company's other birth control product, called Freya-21, is not affected.
Health Canada advises women to:- Use a non-hormonal method of birth control (such as condoms, spermicidal foam or gel) until another oral contraceptive can be obtained.
- Return unopened packages to their pharmacist.
- Report any adverse reactions potentially related to Freya-28 to Health Canada.
- Consult your healthcare practitioner with any questions or concerns regarding the use of oral contraceptives, especially Freya-28.
In April, another company's birth control pills were recalled because they contained an extra week of placebo pills.
One lot of Apotex's Alysena 28 contained too little active drug, which reduces the effectiveness of the pills and raises the possibility of unplanned pregnancy.