Now, the human gestation period can be broken down into three sections, into three stages or three trimesters. So we have trimester one, we have the second trimester and we have the third trimester. And within each one of these trimesters, something important takes place as we'll see in just a moment. And following the third trimester, we have the process of birth, also known as parturition. So let's begin by discussing what takes place within the first trimester. So let's suppose that sexual intercourse did not yet take place and the menstrual cycle of that woman begins.