The Food and Drug Administration is warning that batches of the contraceptive pill Tydemy may have reduced effectiveness and “could result in unexpected pregnancy” if taken.

The agency said it has not yet received any reports of adverse events related to the recalled batches.

Anyone taking the pills is advised to continue but to also immediately contact their health care provider for advice regarding an alternative contraceptive method.

The affected batches were distributed in the U.S. from June 3, 2022, to May 31, 2023, under two lot numbers: L200183 and L201560.

The pills’ packages are marked with national drug codes (abbreviated NDC) reading 68180-904-71 or 68180-904-73.

Testing showed that one of the two lots had high levels of a known impurity and low levels of ascorbic acid, which is an inactive ingredient in the pills, Lupin said.

Inactive ingredients can have uses such as preserving a medicine until its expiration date or helping with the body’s absorption.