Yes, most women have had clots in their menstrual bleeding at least once and usually on several occasions. The size as well as the color varies between women and between periods of the same woman depending mainly on the cause.
Read the full article on: Why do blood clots occur during menstruation? ( 84).

Andrea Rodrigo
B.Sc., M.Sc.
Bachelor's Degree in Biotechnology from the Polytechnic University of Valencia. Master's Degree in Biotechnology of Human Assisted Reproduction from the University of Valencia along with the Valencian Infertility Institute (IVI). Postgraduate course in Medical Genetics.