The "Last Menstrual Period" (LMP) refers to the first day of a woman's most recent menstrual cycle. It is an important date used in various medical contexts, particularly in obstetrics, to estimate a woman's due date for pregnancy. The LMP helps healthcare providers track the progress of a pregnancy and assess the overall health of the woman. Typically, a menstrual cycle lasts about 28 days, but it can vary from 21 to 35 days. Knowing the LMP is crucial for understanding a woman's reproductive health and can assist in diagnosing conditions related to the menstrual cycle or ovulation.