How to tell if you are pregnant? Pregnancy is a topic that every woman is very concerned about, but how do you know if you are pregnant? The following will introduce you to common pregnancy symptoms from many aspects to help you understand the changes in your body. Changes in the menstrual cycle After pregnancy, the endometrium changes, causing changes in a woman\’s menstrual cycle. If your period is late and other factors (such as stress) have been ruled out, pregnancy may be the cause. If you are pregnant, your menstrual cycle will stop and you may experience light vaginal bleeding called implantation bleeding for about 2 weeks after conception.