American pharmaceutical giant Pfizer has announced recall of more than one million packets of birth control pills after it found out that inactive or placebo pill may have been placed out-of-order in some packs.

"We have announced a voluntary recall of Lo/Ovral-28 (norgestrel and ethinyl estradiol) and Norgestrel and Ethinyl Estradiol Tablets (generic) birth control pills in the United States," the company said in a statement yesterday.

"We understand that this news can be very concerning and confusing for any woman who takes birth control pills to protect against unintended pregnancies," it said.

Pfizer said its voluntary recall is based on its own rigorous internal assessments of this problem, in which it found that the inactive or placebo pill may have been placed out-of-order in some packs.

"We believe there are approximately 30 packs of birth control pills that may have received an inexact count or inactive tablet," it said.

"Because of our high quality standards, should we identify even one package that does not meet our high standards, we will voluntarily recall the entire lot," the company said.

Pfizer said it has voluntarily recalled the 28 lots - which is approximately 1 million packs - to ensure that any possibly impacted product is removed from pharmacy shelves - and women who use the product are alerted.