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In some couples, there seems to be nothing wrong. Tests show that everything seems normal. Yet they still can't get pregnant. This is called unexplained infertility and it affects up to 2 in 10 infertile couples.¹

Doctors now think that unexplained infertility is probably caused by a small problem in each partner. On their own the problems wouldn't matter. But if both partners have something slightly wrong it affects the chance of getting pregnant.

For example, a man may have a few sperm that do not move properly. And a woman's eggs may have slight abnormalities that make it hard for them to be fertilized. Or she may have slightly damaged tubes that make it difficult for eggs to pass down them.

If you have unexplained infertility, doctors probably won't try to find out the exact cause. It isn't worth looking for a cause because the treatments are the same anyway. And more detailed tests instead of treatments may waste valuable time.

This information is for educational use only, and is not a substitute for prompt professional medical advice. Readers should always consult a physician or other professional for advice and treatment. ©BMJ Publishing Group Limited 2008. All rights reserved.