Can wheaning a child cause a missed period?

Yes. If you are asking if changing status of breastfeeding can cause you to miss a period, then the answer is yes. It's also possible, that if you are exclusively breastfeeding, and you're past the 6 month mark, without birth control, that you're pregnant. If you've supplemented at all since birth, then also possible pregnant. Consider a pregnancy test if you're at all worried. Best of luck.