Food and Drug Administration advisers, in a recent vote, said the benefits of four popular Bayer AG birth-control pills outweigh the blood-clot risk. What the FDA didn't disclose is that three of the advisers have had ties to Bayer, serving as consultants, speakers or researchers.

The three doctors were members of a special safety committee convened last month to assess the safety of the products, called Yaz, Yasmin, Beyaz and Safyral. Bayer's own studies show no excess danger, but other research including an FDA-commissioned...