Have you heard those stories where a person is pregnant but doesn't know it? These are not the stories where the woman realises that she is pregnant at a later stage of pregnancy. These stories of those women who do not know they are pregnant until a baby comes out of their body. Yes, you read it right. These women have no signs of pregnancy. No baby bump, no weight gain and their clothes fit them perfectly!Among many, this is also the story of an Australian model Erin Langmaid who did not know she was pregnant until 10 minutes before giving birth on the bathroom floor. The now 28-year-old Instagram model on her account posted selfies and photos until 37 weeks without any signs of pregnancy. The then 23-year-old was also on contraceptives and all her clothes fit. This is what experts call a cryptic or stealth pregnancy. A study notes that 1 in about 2,500 women do not realise that they are carrying a child until they are in labour. 1 in 475 do not catch on until they are 20 weeks into gestation. However, the research on this is limited. What Is A Cryptic Pregnancy?A cryptic or stealth pregnancy is when a pregnant person does not know that they are pregnant. In some cases, like Landmaid's, people do not realise their pregnancy until the labour begins. While for most people the realisation occurs when they are about 4 to 12 weeks pregnant. The most common sign is missed period and a positive pregnancy result on home pregnancy test kit. Do You Get Your Period?During cryptic pregnancy, you do not get your period, however, you might experience implantation bleeding or abnormal pregnancy bleeding or spotting and mistake it for your period. What About Pregnancy Test?At-home pregnancy test can show that you are pregnant, however a false negative may also occur. This might make you believe that you are not pregnant. Furthermore, the lack of symptoms and implantation bleeding mistaken for period may add to the confusion. How Can You Not Know?If you are on birth control or use contraception, then you might experience light periods, or sometimes skip periods. This makes it more difficult for you to know whether or not you are pregnant. Women with PCOS often miss their periods for a long time, this can also lead to confusion during a cryptic pregnancy. While weight gain is common in pregnancy, in cryptic pregnancy, your fetus is positioned in a way that the weight is not reflected. Often times, the fetus might also grow at a slower pace than usual and cause it to be undeveloped in the womb.