The time of pregnancy is calculated from the first day of your last menstrual period (LMP), which is typically two weeks before conception actually occurs. This means the first two weeks of the 40-week count are before fertilization, during which your body prepares for ovulation and a new cycle begins
There’s a few days when it’s likely a woman will be fertile. It’s like 8 hours of fertility total. The few days allow sperm to be present during that window. It’s a miracle anyone gets pregnant