With all the help our bodies are programmed to give, the process of getting pregnant may appear ...

The process of becoming pregnant is complex, and there are several potential problems. For example, the female's immune system itself begins to attack the semen immediately after ejaculation, thinking it is unwanted bacteria. Yet, although many sperm are killed by the woman's immune system, this process is usually not a threat to conception. When a fertile woman engages in unprotected vaginal intercourse, 30 of the time she becomes pregnant, although a significant number of these pregnancies end in spontaneous abortion (Zinaman et al., 1996).