Many women may immediately assume that they are pregnant after missing a period for 17 days, but a late period can be caused by a number of circumstances and is not altogether uncommon, according to WebMD. These factors depend on the woman's age and medical history. Causes range from simple hormonal fluctuations to more serious conditions, such as polycystic ovary syndrome, or PCOS.
Any woman who finds that her period is coming later than usual according to her own personal menstrual history and is concerned about the implications of these changes should consult her doctor to be sure that her health is not in jeopardy. According to WebMD, every woman experiences her cycles at different intervals, and it is important for women to be familiar enough with their own bodies to know when their menstrual behavior may signal a problem. Causes of late or missed periods may include perimenopause, menopause, emotional stress, medicinal influences such as birth control, rapid or excessive weight loss or gain, eating disorders, travel or illegal drug use. There is no acute cause to be alarmed unless these symptoms present themselves for some time. However, as is the case with any considerable bodily changes, it is advisable for women to seek a medical professional's advice when unsure of what these changes are signaling.