Unexplained Infertility
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Infertility cases in which the standard infertility testing has not found a cause for the failure to get pregnant. Unexplained infertility is also referred to as idiopathic infertility. Another way to explain it is the “doctors can't figure it out” group.
The definition of what “standard testing” consists of is not agreed upon by all experts. Medical studies have reported that 0-26% of infertile couples have unexplained infertility. The most commonly reported figures are between 10-20% of infertile couples.
However, those percentages are from studies in which all the women had laparoscopy surgery to investigate the pelvic cavity for pelvic scarring and endometriosis. Laparoscopy surgery is no longer done as part of the routine fertility workup. Therefore, we are not finding all of the causes of infertility that we used to - leaving many more couples in the unexplained category.
The current rate of unexplained infertility is about 50% for couples with a female partner under age 35, and about 80% by age 40.
In reality, there are probably hundreds of “causes” of infertility. There are a lot of things that have to happen perfectly in order to get pregnant and have a baby. As an overly simplified example of the science involved:
A weak link anywhere in this chain will cause failure to conceive.
The above list is very oversimplified, but the point is made. There are literally hundreds of molecular and biochemical events that have to happen perfectly in order to have a pregnancy develop.
The standard tests for infertility barely scratch the surface and are really only looking for obvious factors, such as blocked tubes, abnormal sperm counts, ovulation problems, etc. These tests do not address the molecular issues at all. That is still for the future.
The likelihood of a diagnosis of unexplained infertility is increased substantially in women 35 and over - and greatly increased in women over 38. The reason for this is that there are more likely to be egg quantity and quality problems as women age. Since we do not have a “standard category” called egg factor infertility, these couples sometimes get lumped in to the “unexplained” infertility category.
Most women over 40 who try to get pregnant will have difficulty, and fertility over age 44 is rare - even in women who are ovulating regularly every month. The point is that the older the female partner, the more likely that there is an egg related issue causing the fertility problem. Unfortunately, there is currently no specific test for “egg quality”.
The pros and cons of tubal reversal surgery versus IVF for women who have had their tubes tied, clipped, or burned (previous tubal ligation) are discussed on the tubal reversal versus IVF page.
Some experts would also consider infertility associated with mild endometriosis to be in the “unexplained” category. This is because a cause and effect relationship has not been definitely established between mild endometriosis and fertility problems.
In vitro fertilization is a treatment option that bypasses the tubal problem instead of attempting a repair.
With in vitro fertilization, sperm and eggs are mixed together in the laboratory and then the resulting embryos are transferred to the woman’s uterus.
Success rates with in vitro fertilization for tubal factor infertility in women under 39 years old are usually very good because these women are relatively unlikely to have additional infertility problems.
The duration of infertility is important. The longer the infertility, the less likely the couple is to conceive on their own. After 5 years of infertility, a couple with unexplained infertility has less than a 10% chance for success on their own.
One study showed that for couples with unexplained infertility and over 3 years of trying on their own, the cumulative pregnancy rate after 24 months of attempting conception without any treatment was 28%. This number was found to be reduced by 10% for each year that the female is over 31.
Ovarian stimulation and/or intrauterine insemination, IUI Intrauterine insemination vs. timed intercourse (sometimes called sex, or BD, baby dance) – no medications involved.
This has been studied and there is an increased chance for pregnancy with IUI for unexplained infertility as compared to timed intercourse. However, intercourse should be more fun than IUI – and should be cheaper too.
3-6 months of treatment with Clomid pills (clomiphene citrate) might improve fertility by as much as 2 times as compared to no treatment. This is a very low level infertility treatment. Infertility specialists do not usually recommend Clomid treatment( without insemination) for unexplained infertility for women over the age of about 35. Most fertility specialists do not use it (without IUI) on any couples with unexplained infertility. If a woman is already having regular periods and ovulating one egg every month, giving Clomid, which will probably stimulate the ovaries to release 2 or 3 eggs per month (instead of one) is not really fixing anything that is broken – and is not likely to be successful.
Letrozole or Femara is another oral medication that is sometimes used to stimulate development of multiple follicles during infertility treatment.
Several studies showed improved pregnancy success rates with injectable FSH plus IUI treatment as compared to no treatment.
This is less extensively studied. It is not yet known whether the ovarian stimulation and the insemination have independent beneficial effects or whether their beneficial effects are only seen when they are used in combination. Most likely they both independently increase fertility potential, with relatively more fertility benefit coming from the IUI component.
In vitro fertilization (IVF) has high success in young women with normal ovarian reserve testing and unexplained infertility. Most couples with unexplained infertility with a female partner under age 40 will try about 3 artificial inseminations and if not pregnant – do IVF.
IVF also can give us clues as to the cause of the infertility. For example, we may see low fertilization rates per egg, or we may see slow embryo development, excessive fragmentation of the embryos, abnormal eggs, abnormal egg shells (zona pellucida), etc…