Trying to get pregnant with baby number two at 40! your fertile window begins when estrogen starts to rise. Here’s how it works: \t•\tWhen estrogen first begins to rise (produced by your growing follicles), it signals that your body is preparing for ovulation. \t•\tRising estrogen causes cervical mucus to become clear, stretchy, and slippery — the ideal environment for sperm survival. \t•\tThis marks the start of your fertile window, which usually begins about 5–6 days before ovulation. \t•\tThe