A woman's period can be delayed for an undetermined period of time and for a number of reasons, according to the Mayo Clinic. Several factors can cause a delayed period. The most common reason is pregnancy.
If a woman misses three consecutive periods, she technically has a condition called amenorrhea, according to the Mayo Clinic, which is also the cause if a girl has not had her period by the age of 15. A period could also be delayed due to a hormonal imbalance, according to About.com. Polycystic Ovarian Syndrome could lead to amenorrhea, and stress can also delay a woman's period, according to About.com.