The expected date of delivery (EDD) is 40 weeks counting from the first day of the last (LMP), and birth usually occurs between 37 and 42 weeks. Though Pillows For Pregnancy begins at , it is more convenient to date from the first day of a woman’s last menstrual period, or from the date of conception if known. Starting from one of these dates, the expected date of delivery can be calculated using the for estimating date of delivery. A more sophisticated algorithm takes into account other variables, such as whether this is the first or subsequent child (i.e., pregnant woman is a primip or a , respectively), ethnicity, parental age, length of menstrual cycle, and menstrual regularity.