A woman's period can arrive late because of excessive stress, hormonal imbalances, severely decreased body fat or the use of birth control, according to Zahra Barnes for Women's Health. Premature ovarian failure, polycystic ovarian syndrome, chronic illness or early menopause can also cause late periods.
Late periods are commonly an early sign of pregnancy, explains pregnancy and childbirth expert Robin Elise Weiss for About.com. Weight fluctuations that cause a woman to become too thin or overweight also influence the body's hormones and can create an internal environment that alters a woman's menstrual cycle. If a woman is placed on a new birth control or switches medications, it is common for her cycle to experience an interruption as the drugs rebalance her hormones.
Some women may simply miscalculate their menstruation date and not have a late period at all. Sudden illnesses are also known to delay the onset of menstruation, but Weiss notes that this is usually a temporary change and often sorts itself out when the body returns to good health. If women do not maintain a consistent schedule at work, it is possible that frequent changes in shift hours can confuse the body and throw a woman's menstrual cycle out of balance. Women are encouraged to visit with a doctor to rule out any underlying health complications.