NEW YORK (CNNMoney) -- Discounter Wal-Mart and drugstore CVS said they are reviewing the Food and Drug Administration approval Thursday of the over-the-counter sale of its "morning-after" pill and could decide to sell it without prescription in their stores.

Wal-Mart (Charts), the No. 1 retailer, began stocking Plan B contraceptives - commonly referred to as the "morning-after pill" - at all of its pharmacies on March 20 this year.

At the same time, the company said it would maintain its conscientious objection policy, which lets employees who don't feel comfortable dispensing a prescription to refer customers to another pharmacist or pharmacy.

In a statement e-mailed to CNNMoney.com, company spokesman Kevin Gardner said Wal-Mart was awaiting details of what was approved by the FDA and specifically how the product can be sold [over the counter].

"Once we have those details, we will consider carrying the product for OTC," he said.

Mike DeAngelis, spokesman for CVS (Charts), the No. 2 drugstore chain behind Walgreen (Charts), said the company would not take any actions until it had reviewed the FDA's formal ruling on the matter.

"Once the FDA has made its review on Plan B available to us, we will review it and then work with the manufacturer to understand the new regulatory requirements surrounding the sales of Plan B without a prescription," DeAngelis said.

Over-the-counter Plan B will only be available to women 18 years and older. Women 17 years and younger still will need a prescription.

DeAngelis said nonprescription Plan B won't be available at CVS stores anytime soon.

"The manufacturer has indicated they would have to create new packaging to allow for dual OTC sales. This won't be available until the end of the year. So we'll use this timeframe to develop our procedures for selling non-prescription Plan B," DeAngelis said.

'Morning-after' pill wins key FDA approval.