For many years now an association between talcum powder and ovarian cancer has been mooted but never, in my opinion, proven outright. Some studies have shown a slight increased risk with long-term use of Talcum Powder as a female hygiene aid. Other studies have failed to show such a risk. In a situation like this the term 'equivocal' is often used. If there is in fact an association between talcum powder and ovarian cancer then it is a very weak one.
Here is what The American Cancer Society has to say on the subject: