The text explains why a partner can still become pregnant even when the withdrawal method is used. It highlights that a small amount of pre-ejaculatory fluid can contain a significant number of healthy sperm. These sperm are capable of moving quickly through the reproductive tract toward the fallopian tubes. Once they reach the egg, fertilization can occur, leading to an unintended pregnancy. This demonstrates that the withdrawal method is not a foolproof way to prevent conception. Understanding the mobility and presence of sperm in small amounts of fluid is crucial for reproductive health. Therefore, more reliable forms of contraception are recommended to avoid unwanted outcomes.