October pregnancy is defined as a gestation period of 40 weeks, or 280 days, with each gestational month being 28 days. Medically, the due date is calculated from the 1st day of the last menstrual period, and the normal pregnancy time frame is about 265 days. The calculation starts from the 1st day when the egg is fertilized, and ovulation is in the middle of the menstrual period, so 40 weeks, 280 days, is 2 weeks more than the pregnancy time calculated from the actual egg fertilization. Women who are sexually active should suspect that they are pregnant and should seek medical attention to confirm the diagnosis if their previously very punctual period is about 10 days late, if their breasts inexplicably increase in size, if their areola color deepens, if they are mentally tired, and if their body temperature increases. If you are pregnant, you can calculate the expected date of delivery based on the date of your last menstrual period by: month = month of last menstrual period + 9 (or -3); date = date of last menstrual period + 7.