900 is so different than 5

If a very large number of women use combined birth control pills for one year, 900 become pregnant

If the same number of women, ten thousand women is the number, use a Nexplanon implant, 5 become pregnant in the next year.   

Professor James Trussell’s Table 3-2 of contraceptive failure rates is in the source of these numbers.  His table on page 50 of the book Contraceptive Technology (20th edition) states that the first year failure rate for Implanon and Nexplanon is 0.05% which is 5 per 10,000 women.

The same table lists the first year failure rate of combined and progestin only pills as 9% which works out to be 900 per 10,000 women.

Robert A. Hatcher MD, MPH
Professor of Gynecology and Obstetrics
Emory University School of Medicine
Atlanta, Georgia