Can the pill cause breast enhancement?

Yes: It can make breast enlarge a half a cup size in some people.

Sort of: Most birth control pills are synthetic female hormones, estrogen and Progesterone like the female body makes in a normal menstrual cycle. Just like during a menstrual cycle breasts can fluctuate in size with changing hormone levels but the result is not as predictable or sustained as with an augmentation. Also keep in mind the increased risk of blood clots with birth control pill use?

No: There are no effective nonsurgical ways to increase breast size. Stay away from heavily marketed medicines, creams, technologies that promise otherwise.