Hello, and I hope I can help you today. Having your period come late or skip occasionally is common in many women, even when they are not pregnant. Most of the time, a delayed period can just be a chance event, but it also can be cause by stress, changing time zones or traveling, recent weight gain or weight loss. If that is the case, you usually will get it somewhere between 2 and 4 weeks late. A fall usually will not affect your menstrual cycle, unless the stress of your injury was a factor. Either way, there is nothing dangerous about missing your period once and a while. If you miss your period for more than 3 months, you should see a gynecologist so you can be evaluated for hormone imbalanced and the doctor can prescribe appropriate medication to help your period to come. If you are at risk for pregnancy (meaning if you had unprotected sex in the last three weeks), you should repeat the pregnancy test in a week or so just in case. I hope I was able to adequately answer your question today and that my advice was helpful. Best wishes, Dr. Brown