Prevalence of Infertility in Industrialized Countries
Infertility is defined as the absence of pregnancy after one year of regular intercourse without contraception. About 17% of couples in industrialized countries seek medical assistance for this reason. According to the World Health Organization, female factors account for 37% of infertility cases and are associated with a number of diseases and conditions. Let’s examine the most common ones:
Ovarian Insufficiency: The main causes
- Ovarian dysfunction accounts for 25% of female infertility cases. It can be associated with various factors, including ovulation disorders—irregular ovulation (oligo-ovulation) or anovulation. The World Health Organization’s classification of ovulation disorders (Ovulation Group 3) is used to detect and treat these disorders:
- Normal estrogen, hypogonadotropic hypogonadism, as seen in polycystic ovary syndrome (PCOS).
- Hypoestrogenic hypergonadotropic—premature ovarian failure.
- Anovulation with hyperprolactinemia, for example, with hypothyroidism and hyperthyroidism.
Egg aging is another factor in female infertility. The number and quality of eggs decrease with age. Girls have between one and two million follicles at birth and about 300,000 follicles at the onset of puberty. After age 35, the rate of follicle loss significantly increases, accelerated by smoking, radiation, and autoimmune diseases. Women with diminished ovarian reserve may ovulate regularly, but due to the poor quality of the eggs, they cannot conceive.
Tubal Abnormalities and Pelvic Adhesions:
Tubal factors account for 11% of female infertility cases and pelvic adhesions in 12% of cases. Both conditions prevent the normal movement of eggs and sperm through the fallopian tubes. The main causes of tubal factor infertility include:
- Pelvic inflammatory disease (PID) associated with chlamydia, gonorrhea, or other pathogens.
- Severe endometriosis.
- Adhesions after previous surgery.
- Appendicitis, inflammatory bowel disease, and other inflammatory conditions in the abdomen.
- Fallopian tube diverticula (nodular salpingitis, SIN).
- Tubal polyps.
In women with distal fallopian tube blockage, hydrosalpinx—fluid accumulation in the tube cavity—may develop. This reduces the success rate of in vitro fertilization (IVF). Hydrosalpinx prevents sperm migration and also leads to retrograde flow of fallopian tube contents into the endometrial cavity, creating a hostile environment for embryo implantation.The main causes
Uterine Diseases and Abnormalities:The main causes of infertility in women
The primary cause of uterine infertility is embryo implantation disorder. Uterine fibroids (leiomyomas) are common benign tumors of smooth muscle. Fibroids with submucosal and intracavitary components may reduce pregnancy and implantation rates. Hormonal changes in the hypothalamic-pituitary-ovarian-uterine axis are considered the main factor in reproductive dysfunction in uterine fibroids. Many fibroid patients experience ovulatory cycles with varying levels of estrogen saturation or biphasic cycles accompanied by luteal phase deficiency. Mechanical factors also play a role, such as when a fibroid in the tubal corner compresses the interstitial portion of the tube, interfering with its patency. Surgical removal of the fibroid increases the likelihood of implantation.
Congenital uterine abnormalities are important causes of infertility and miscarriage. A unicornuate uterus forms when one Müllerian duct halts or slows in growth while the other develops normally. With such an anomaly, pregnancy is possible, but its outcome depends on the uterus’s size. A bicornuate uterus results from incomplete fusion of the middle portion of the Müllerian ducts. It contains two cavities and one cervix, often two, connected to a normal vagina or one separated by a partial septum. The two halves of the uterus, The main causes separated by a septum, are associated with the worst reproductive outcomes.
Endometrial polyps and synechiae also lead to female infertility. Causes of synechiae include:
- Incomplete abortion.
- Missed miscarriage.
- Hydatidiform mole.
- Postpartum hemorrhage.
- Retained placental tissue.
Endometriosis as a Cause of Infertility:
Endometriosis is one of the most common reproductive-age diseases. While healthy women have a 15-20% chance of conception in any given menstrual cycle, untreated women with reproductive endometriosis have a 2-10% chance. Endometriosis is responsible for 15% of female infertility cases. This is a multifactorial disease in which benign endometrial tissue grows beyond its normal site.
Current theories do not fully reveal the true etiology of endometriosis-associated infertility. However, insights exist regarding tubal factor, ovarian dysfunction, changes in endometrial receptivity, and more. Special attention is given to progesterone resistance, which is linked to a reduced total number of progesterone receptors. This disease impairs the expression of The main causes progesterone-stimulated proteins important for endometrial implantation and receptivity.
Other Causes of Infertility:
Cervical Factors: Normal cervical mucus facilitates sperm transport mid-cycle. With congenital abnormalities and cervical injuries, including surgical injuries, stenosis may occur, and the cervix may be unable to produce normal mucus, reducing fertility.
Immune Factors: Women with certain autoimmune diseases have an increased risk of infertility unrelated to the direct effects of antibodies on fertilization and implantation. For example, premature ovarian failure has been described in women with systemic lupus erythematosus and myasthenia gravis. Autoimmune oophoritis can occur as part of type I and type II autoimmune polyendocrine syndromes. Untreated celiac disease patients may also have an increased incidence of reproductive disorders, including infertility, miscarriage, and intrauterine growth restriction.
Genetic Causes: It has been shown that infertile couples have a higher prevalence of karyotype abnormalities (trisomies, mosaicism, translocations) than the general population. The frequency varies depending on the cause of infertility and medical history. Scientists have also identified individual genes that affect fertility, including KAL1, FSH receptor, TUBB8. Mutations in the latter are unique in that they only affect eggs, disrupting microtubule function during oocyte division and arresting its maturation.
Unexplained Infertility is a diagnosis of exclusion. Many cases of unexplained infertility may be associated with the slight influence of several factors simultaneously.
Causes of Male Infertility:
The treatment of male infertility mainly depends on the cause of infertility, which is often due to one of the sperm disorders such as:
1️⃣ A lower-than-normal sperm count.
2️⃣ Problems with the seminal fluid.
3️⃣ Ejaculation-related issues, which stem from four main causes:
Endometriosis as a Cause of Infertility
1️⃣ Secondary hypogonadism, resulting from some disorders of the pituitary gland or hypothalamus in the brain, responsible for secreting hormones that stimulate the testes to produce testosterone, constitutes 1-2% of male infertility cases.
2️⃣ Primary testicular disorders, such as orchitis, varicocele, and some problems related to the growth and development of the testes, account for 30-40% of male infertility cases.
3️⃣ Disorders in sperm transport, accounting for 10-20% of male infertility cases.
4️⃣ Unknown causes, which make up 40-50% of infertility cases.