Not all couples who come to see the fertility doctor are childless. Many couples, in fact, have had children prior, or have gotten pregnant prior and terminated pregnancies, but are now having difficulty conceiving. When a woman has a previous child or a previous pregnancy, and is now infertile, we use the term "secondary infertility." The causes for secondary infertility are generally the same as the causes for primary infertility.
Fallopian tube disease can occur after a prior pregnancy, uterine abnormalities, including scar tissue, ovulation dysfunction, poor number of eggs. All those can absolutely occur in secondary infertility cases, just as they have in primary infertility. The same is true with the male. A man's sperm can decrease over time, and men could have poor sperm quality over time. So it's very important that a secondary infertility evaluation include all the causes that were in the primary fertility evaluation. It's a mistake for women to assume that, just because a man has fathered a prior child, that his sperm is normal. And it is a mistake for the couple to also think that just because a woman got pregnant before, that there is no possibility that she will have a problem getting pregnant again.