Conception and pregnancy are complicated processes that depend upon a number of factors, including:

1. The production of healthy sperm by the man.
2. Healthy eggs produced by the woman.
3. Unblocked fallopian tubes that allow the sperm to reach the egg.
4. The sperm's ability to fertilize the egg when they meet.
5. The ability of the fertilized egg.
6. (Embryo) to become implanted in the woman's uterus.
7. Sufficient embryo quality.

Finally, for the pregnancy to progress to full term the embryo must be healthy and the woman's hormonal environment adequate for its development. If just one of these factors is impaired, infertility can be the result.