The causes of infertility are many and varied, and as about 20% of infertile couples are given an “unexplained” diagnosisi in the USA (where most women have a laparoscopy to check for endometriosis (or other pelvic problems) that’s rarely part of the fertility “work-up” in other countries), it shows the scale of the problem. Because of the differences in diagnostics, it’s possible that known causes of infertility won’t be found in many countries, and some authorities have suggested higher rates for unexplained infertility according to age:
- About 50% for women under 35
- About 80% for women aged 40ii
When couples have standard fertility tests they check for the main reasons for infertility, including:
- Hormonal imbalances
- Not ovulating
- Tubal blockages
- Poor semen results
There’s ongoing research into developing better tests for less obvious factors that reduce fertility, and these will hopefully reduce the number of couples being diagnosed as ‘unexplained’. Having a definite view on why people have ‘unexplained infertility’ is essentially contradictory and depends on the person you talk to (so not everyone will agree with all of these) but the eight main possibilities are thought to be:
- Endometriosis (particularly mild endometriosis) has strong links with infertility, and early stage endometriosis is believed to trigger a strong immune response in the pelvic cavity, increasing the number of white blood cells and causing very high cytokine levels around the fallopian tubes and ovaries, which can easily kill sperm. Many women with mild endometriosis are symptom free, and without a laparoscopy no-one would suspect they were affected
- Age affects both male and female fertility and after 30 there’s a fall in the genetic integrity of sperm and eggs, which for men can be assessed with additional semen tests. There aren’t currently tests for “egg quality” but it’s possible to use AMH and FSH levels to assess the ovarian reserve and how hard the body has to ‘work’ to get eggs recruited each cycle
- Immune issues are a definite player in the unexplained infertility scenario as there’s increasing evidence of the complex and sometimes conflicting role the immune system plays in getting pregnant. However not that many people get tested for their immune status as these are relatively new (and expensive) tests so quite how important it is hasn’t been quantified. What is certain is that an unbalanced immune system makes it much harder to conceive
- Hypothyroidism is a widespread (but often undetected) condition that reduces fertility and is associated with known infertility conditions like endometriosis, and that in a pregnancy the body’s need for thyroid hormones increases. There are many people trying to get pregnant who have no idea they have subclinical hypothyroidism and that it reducing their fertility
- “Folate pathway replication of the DNA and RNA” is all about the ability of cells to develop and divide properly, which is absolutely essential as an embryo grows. The issue here
I ‘Unexplained Infertility Background, Tests and Treatment Options’. R. Sherbahn MD. ‘Advanced Fertility Center of Chicago’
ii ‘Unexplained Infertility Background, Tests and Treatment Options’. R. Sherbahn MD. ‘Advanced Fertility Center of Chicago’
iii “Variations in folate pathway genes are associated with unexplained female infertility”. Altmäe, S. et al; (2010). Fertility and Sterility 94 (1): 130–137.
iv Demirol A, Gurgan T. Effect of treatment of intrauterine pathologies with office hysteroscopy in patients with recurrent IVF failure. Reprod Biomed Online May 2004;8(5):590-94.
v“Azem F, Many A, Yovel I, Amit A, Lessing JB, Kupferminc MJ. Increased rates of thrombophilia in women with repeated IVF failures. Human Reproduction February 1, 2004;19(2): 368-70.
vi “Bacterial vaginosis and infertility: cause or association?” Salah RM, Allam AM, Magdy AM, Mohamed ASH. Eur J Obstet Gynecol Reprod Biol 2013; 167:59–63.