Pregnancy is that period of time when a fetus begins to grow in the uterus until the end of the pregnancy when the baby is born. Throughout this time, a woman routinely goes through several laboratory tests, which detect specific problems that crop up from time to time during pregnancy. These problems might be a result of advanced age or lifestyle or family history of the mother to be. A woman’s date of delivery is calculated from the first day of her last menstrual period to the next 37-42 weeks, though the expected date of delivery is set at 40 weeks.