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Infertility is a term that is defined as the inability of couples to become pregnant after one year of regular intercourse without contraception, or 6 months if a woman is 35 years or older. Infertility can occur in both females and males, and there are many causes. In order to get pregnant, a woman's body must go through three main steps: ovulation, fertilization, and implantation. In ovulation, an egg is released from one of her ovaries, which then travels down to one of the fallopian tubes and into the uterus. The egg must then be fertilized by the sperm during the process of fertilization. Finally, in implantation, the fertilized egg implants itself in the uterine wall. When there are problems in any of these steps, infertility can be diagnosed. In this paper, three causes of infertility in females will be explained: endometriosis, uterine fibroids, and premature ovarian failure. Several literature reviews will be used in an attempt to state and support the three causes of infertility.
One of the leading causes of infertility is endometriosis, where the endometrial tissue grows outside of the uterus (Ozkan, Murk, and Arici 2008). This disorder is found primarily in women of reproductive age. In an article by Ziegler, Borghese, and Chapron (2010), mechanisms in which endometriosis could affect fertility were investigated. Endometriosis can occur in the pelvic cavity, ovaries, or uterus. In the pelvic cavity, retrograde menstruation is the primary mechanism for the occurrence of endometriosis (Ziegler et al. 2010). Retrograde menstruation is the backward flow of small amounts of menstrual fluid into the fallopian tubes instead of being expelled out of the body through the vagina. Although this is normal in most women, some of the menstrual fluid can drip into the pelvic cavity, where the endometrial tissue that is present in the menstrual fluid sticks to one of the pelvic organs and starts to grow if it is not removed by the immune system, mainly the macrophages that are part of the immune system. If one of the organs is the ovaries, cysts that contain endometriomas, or old blood, can form and rupture, which can interfere with normal ovulation by reducing the amount of ovarian tissue (Ziegler et al. 2010; Holoch and Lessey 2010). Endometriosis in the uterus is not very common, but possible. In the uterus, abnormal alterations of the endometrium are led by an overproduction of oestradiol and a deficiency in progesterone (Ziegler et al. 2010). The imbalance of both of these hormones can result in disorders of the corpus luteum such as luteinized unruptured follicle syndrome and luteal phase defect (Bulletti et al. 2010). Progesterone is necessary to prepare the endometrium for implantation of a fertilized egg. A deficiency in progesterone would prevent this implantation. All of these mechanisms lead to inflammation, scarring, and adhesions of pelvic organs (Bulletti et al. 2010). Therefore, these mechanisms would distort the pelvic anatomy and cause infertility.
Another cause of infertility is fibroids (leiomyomata). Fibroids are benign tumors that occur in the myometrium of the uterus and rarely show symptoms (Hart 2003). They grow in estrogen-rich environment. Fibroids differ in size, location, composition, and number, and fluctuations in any of these factors can affect a women's fertility (Pritts, Parker, and Olive 2009). Fibroids can cause infertility by altering the shape of the uterine cavity and/or cause abnormal uterine contractions, all of which can impair sperm migration, ovum transport, and embryo implantation (Somigliana et al. 2007). Different anatomical positions of the fibroids have different impacts on a woman's fertility. There are three types of fibroids: submucosal fibroid, which develops just under the lining of the uterine cavity, intramural fibroid, which develops within the wall of the uterus, and subserosal fibroid, which develops just outside the uterine cover. Submucosal fibroids are more severe. They can lead to local inflammation and result in an unstable environment of the endometrium, which interferes with sperm transport and embryo implantation (Hart 2003; Somigliana et al. 2007). When intramural fibroids are near the cervix, which is rare, or near the proximal or distal openings of the fallopian tubes, there may be a distortion of the uterine anatomy, which can lessen the chances of ejaculated sperm accessing the tubes, thus preventing fertilization of an egg (Casini et al. 2006; Somigliana et al. 2007). Large subserosal fibroids create blockages and can impair the fallopian tubes from retrieving an egg during ovulation (Somigliana et al. 2007). This also prevents a sperm and an egg from meeting, thereby causing infertility.
The last cause of infertility is premature ovarian failure (POF). POF differs from menopause in that menopause occurs at an average age of 50.7 years while menopause before the age of 40 is termed as 'premature ovarian failure' (Goswami and Conway 2007). POF is characterized by primary amenorrhea and secondary amenorrhea (Beck-Peccoz and Persani 2006). Women with POF have low levels of estrogen and high levels of follicle-stimulating hormone (FSH) (DragojeviÄ‡-DikiÄ‡ et al. 2010). This demonstrates that no positive feedback is present for the production of estrogen with the increasing levels of FSH. The causes of POF are usually idiopathic, but can be chromosomal, genetic involving the X chromosome, or an autoimmune ovarian damage where anti-ovarian antibodies are estrogen-deficient for up to three months each year (Goswami and Conway 2007). There are two mechanisms through which POF occurs: follicle dysfunction and follicle depletion (Nelson 2009). A woman with follicle dysfunction still has follicles left in her ovaries, but the follicles are not functioning properly. One cause for follicle dysfunction is an autoimmune attack where the body's immune system attacks developing follicles (Nelson 2009). A woman with follicle depletion has no functioning follicles left in her ovaries. The cause for the disorder of follicle depletion can be genetic, specifically an anomaly on the X chromosome (Goswami and Conway 2007). One mature follicle is needed to release an egg each month, and this process can be impaired by premature ovarian failure due to follicle dysfunction or follicle depletion, thus causing infertility.
In conclusion, endometriosis, uterine fibroids, and premature ovarian failure are three causes that play a role in infertility of women. These three disorders have their own causes, and they impair the process of ovulation, fertilization, or implantation, the three steps necessary for fertility. Several articles were used to explain these disorders and support their causes for infertility, although many of them were vague in explaining the direct relationship between these disorders and infertility in women. While these disorders were described in great details of the causes and the effects they have on the body, their links to infertility were not as detailed. More research can be suggested so that better understanding of this relationship can be established and treatments can be discovered, all of which would be beneficial to infertile couples.