Amazon.com Inc has placed a temporary purchase limit of three units per week on emergency contraceptive pills, the company says.

The move comes days after the US Supreme Court overturned the landmark 1973 Roe v Wade ruling that recognised women's constitutional right to abortion.

Women with unwanted pregnancies in the country now may face the choice of travelling to another state where the procedure remains legal and available, buying abortion pills online or having a potentially dangerous illegal abortion.

The ruling has also had an impact on the demand for over-the counter emergency contraceptive pills, known as Plan B, which are taken within days of sexual intercourse.

Pharmacy chain CVS Health Corp said on Monday it was implementing a temporary purchase limit of three on emergency contraceptive pills Plan B and Aftera while Walgreens Boots Alliance said it had no purchase limit in place for Plan B pills at this time.