Unexplained infertility, also called idiopathic infertility, is the medical term used to describe fertility problems without a known cause. When doctors cannot figure out the cause of infertility, they call it “unexplained infertility.” Clinical studies show that around 10-25% of infertile couples have unexplained infertility.
The duration of infertility is a significant factor. The longer the couple are infertile, the less likely they are to conceive. After 5 years of infertility, a couple has less than a 10% chance of getting pregnant without assisted reproductive technology (ART).
Steps of Pregnancy
The current rate of unexplained infertility is around 50% of couples with a female partner age 35 and younger, and about 80% by the time the woman reaches 40 years. To become pregnant, hundreds of biochemical and molecular events must occur in perfect order. Any problem with one of these steps will result in infertility. The steps of pregnancy are:
The pituitary gland and the brain produce hormones that stimulate egg development.
The egg must form of sufficient quality and be chromosomally normal.
The egg should develop to maturity.
The brain must release luteinizing hormone (LH) to simulate egg maturation.
The follicle (structure that holds the egg) must rupture to release the egg.
The sperm must make its way through the vagina, enter the cervical mucous, swim up the uterus, enter the fallopian tube, and find the egg.
The sperm must pass through the cumulus cells around the egg, bind to the zona pellucida (shell of the egg), and release DNA into the egg (23 chromosomes).
The fertilized egg should divide, develop into an embryo, pass down the tube, and enter the uterus.
The blastocyst then must “hatch” from the shell and implant into the endometrial lining.
Female Age and Infertility
The standard tests for infertility look for obvious factors, such as abnormal sperm counts, blocked fallopian tubes, and ovulation problems. Unexplained infertility is more likely to be diagnosed in women age 35 and older. The reason is that these women have more problems with egg quality and quantity, which is difficult to diagnosed. Egg problems usually get lumped into the “unexplained” category regarding infertility.
Infertility associated with mild endometriosis is often linked into the unexplained infertility category. The cause and effect relationship between endometriosis and infertility has not been definitely established.
Ovarian Stimulation and Intrauterine Insemination (IUI)
Intrauterine insemination is used to assist women with unexplained infertility. Ovulation stimulation involves use of certain drugs, such as Clomid. Success rates for Clomid and IUI are around 10% per cycle, and the pregnancy rate holds up for around 3 tries. Clomid stimulates the ovaries to release 2-3 eggs per month, instead of only one, which increases the likelihood of fertilization.
Injectable follicle-stimulating hormone (FSH), which is called gonadotropin, is used to increase pregnancy chances. Researchers are unsure whether the ovarian stimulation and insemination have independent beneficial effects or whether the effects are only seen when these drugs are used with IUI.
In Vitro Fertilization (IVF)
In vitro fertilization (IVF) is a form of ART that improves pregnancy success rates for couples with unexplained infertility. Most couples try IVF after failing on 3 attempts at artificial insemination. IVF can be useful for diagnosing the cause of infertility. The fertility specialist can assess embryo development, egg quality, and abnormal zona pellucida.