A pregnancy can hide itself, known as a cryptic or stealth pregnancy, for a significant amount of time. Typically, most people realize they are pregnant between 4 to 12 weeks into the pregnancy. However, in rare cases, pregnancy can remain hidden for months, sometimes even until labor begins or delivery. Studies suggest about 1 in 475 pregnancies go unnoticed until around 20 weeks, and about 1 in 2,500 pregnancies remain undetected until delivery. This phenomenon can occur due to irregular menstrual cycles, lack of common pregnancy symptoms, false negative pregnancy tests, or misinterpretation of symptoms as other illnesses or conditions. A cryptic pregnancy usually lasts the same length as a regular pregnancy—around 40 weeks—but the person may not be aware of it for most of that time.