My mate and I have been trying to get pregnant for six years (I'm 31 and he's 33) and have been seeing a fertility specialist on and off for three years. We are infertile with no diagnosed cause. We have tried drugs and intrauterine insemination and now, it seems, in vitro fertilization is our next option. I'm not sure I want to take that step without a definitive diagnosis. Is it okay to proceed even if they don't know why we're infertile? What are the chances that we'll never get a diagnosis? --Jessica

In vitro fertilization (IVF) is not only a treatment for infertility, it is also a diagnostic test. Your health care team will learn a lot by seeing how you respond to high-dose hormonal stimulation, how healthy your eggs look, whether fertilization occurs, and the state of your embryos (do they divide, implant? are they healthy?). In vitro fertilization is an appropriate treatment option for those who have undergone successful ovulation induction and insemination cycles without a pregnancy.

As for whether a diagnosis can be found in your case, one can only hope. Researchers are making great strides in the area of unexplained infertility. Studies exploring the role of the immune system and implantation and growth of the early embryo hold promise. Anti-ovarian antibodies and anti-endometrial antibodies may also explain some cases of unexplained infertility. Another area of study focuses on a molecule known as beta-integrin and the role it may play in the embryo's attachment to the uterine lining. Much of this research is still in its early stages; still, I'm optimistic that we'll have improved diagnostic tests available for you and others in the future.