Causes for Infertility
The causes of infertility could be originated from both women and men. Actually, female factor and male factor each contributed to 40% of the infertility couples. 10% of the couples are caused by unknown factors and 10% are caused by both parties.
2.1 Infertility in Men
2.1.1 Disorder in sperm production
The major male problem causing infertility is the disorder in sperm production and it accounts for 75% of the male infertility problems. Besides the reduced sperm count, it also includes poor sperm motility and abnormal morphology.
The defects may be due to genetic causes, smoking, alcohol, chemical pollution exposure, genital tract surgery, vein congestion in scrotum and infection. Often the cause cannot be found.
2.1.2 Anatomical or structural problems
The sperm is manufactured in the testis and is then stored in the coiled tubules surrounding the testis. During intercourse, the sperm will be propelled by the vas deferens into the urethra and ejaculated in the form of semen. That is why blockages along any point of the pathway may cause infertility.
2.2 Infertility in Women
2.2.1 Advanced Age
Relationship between age and egg reserve
As quoted from the Census and Statistics Department, the median age at first delivery was postponed by 4.7 years to 29.8 years-old from 1981 to 2008. This may be one of the reasons contributing to the increasing infertility rate in Hong Kong.
The number of eggs in women is limited and starts to decline from birth, as the ovary does not produce any new eggs after the embryo stage and it continues to diminish from childhood due to egg degeneration. When puberty is reached, egg loss continues due to ovulation with other non-ovulating eggs undergoing atresia. Apart from the reduced quantity of eggs, egg quality also deteriorates as age increases. The live birth rate actually declines by approximately 1% each year as the woman ages.
Relationship between age and miscarriage
There is a higher incidence of endometriosis and uterine fibroids as women get older. These defects may distort the uterine lining and cause a higher risk of miscarriage. The miscarriage rate is 33% in older women while it is only 10% in younger women.
Relationship between age and success rate of ART
Age is also an important factor for the success in ART treatment. ART success rate can reach 50%-60% for women under 30, 30%-40% at the age of 30-40 and the rate decreases rapidly to 20% and below after the age of 40. Due to the correlation of age and fertility, couples are generally advised to seek medical advices as early as possible.
2.2.2 Ovulation Disorders
Ovulation disorders accounted for 40% of the female infertility. There are various causes for this; the most common cause is Polycystic Ovarian Syndrome (PCOS).
Polycystic Ovarian Syndrome (PCOS)
Multiple tiny cysts exist in the ovaries of PCOS patients. These cysts are not harmful to the body, however, it can cause irregular or no ovulation and so increases the chance of infertility. The affected women may show raised blood hormone LH:FSH ratio and testosterone level, increased body weight and/or body hair, acne and abnormal insulin level.
Premature Ovarian Failure
Under normal circumstances, the ovaries run out of eggs and stop functioning at menopausal age. Yet, various unknown reasons may cause ovarian failure in younger women. Some studies suggest that this condition may be due to the exposure to chemical or medical treatments, various autoimmune diseases and genetic disorders.
Amenorrhea refers to the condition of no mense. This occurs when there is no gonadotropin-releasing hormone (GnRH) production in the hypothalamus. Women undergone constant stresses, abrupt change in weight, excessive exercise and lack in nutrients, have an increased chance of amenorrhea. Genetic abnormalities may contribute to some of the cases; however, the chances are very rare.
2.2.3 Structural Problems in Female Reproductive System
Endometriosis occurs in 5%-10% of the general women at reproductive age. It refers to the medical condition in which the endometrial like tissue grows in areas other than the uterine cavity. Symptoms often worsen with time of the menstrual cycle due to the increase of various female hormones. The abnormal endometrial tissue may affect ovulation or obstruct the Fallopian tubes and the fertilization process.
A uterine fibroid is a benign tumor which originates from the smooth uterine muscle layer and the connective tissue. It often occurs in women of middle and later reproductive years. Some of the affected women may have no symptoms while others may suffer heavy menstruation flow, urinary frequency, urgency, painful menstruation and sexual intercourse. The fibroids could be very small or occur in location that they will not affect any reproductive functions. However, if the fibroid is large and if it is located inside the uterine cavity, it may have large impact on reproductive functions. Fibroids can often be cured by surgery to improve fertility.
Tubal disease is one of the common factors causing infertility. The Fallopian tube is the pathway travelled by sperms to reach the egg after it has been released from the ovary and it is where fertilization occurs. The fertilized embryo then travels along the tube to reach the uterus where implantation occurs. The women affected by tubal disease may have both or just one tube blocked. Other times, there can be simply tubal scarring or other tubal damage without tubal blockage.Tubal disease is often caused by either pelvic infection or pelvic endometriosis. It may also be the scar tissue formed after pelvic surgery. IVF is a promising method in treating infertility caused by tubal factor.
Hyperprolactinemia happens when the pituitary gland produces excessive amounts of the hormone, prolactin. Prolactin is a hormone generally produced after delivery for the suppression of ovulation. The abnormal production of prolactin suppresses GnRH release hence ovulation. Hyperprolactinemia can be due to no identifiable cause or microprolactinoma in the pituitary; treatment is possible by using medication such as e.g. Bromocriptine, Quinagolide and Cabergoline.