This week we will continue on the topic, focusing on causes of Anovulation and how it affects fertility and pregnancy outcome.
Anovulation is the major cause of infertility which accounts for about 30% and often presents with oligomenorrhea (infrequent menstruation) and amenorrhea (absence of menstruation). Considering this high prevalence rate, anovulation therefore, is a major cause of infertility. There are several predisposing factors to anovulation including bad diet, advancing age in women, smoking, excessive alcohol intake, addictive exercise and genetics.
Infertility has been a prevalent problem in our society. For few years, the reasons for infertility have become popular topics in the press. This has led to increased awareness of infertility and significant advances in the discovery of causes and various predisposing factors to it.
As earlier explained, in a normal menstrual cycle, the female ovary releases a mature egg/ovum in a process known as ovulation. This period in a woman’s menstrual cycle marks her most fertile period when a sperm cell, can fertilize the released egg, following unprotected sexual intercourse leading to a potential pregnancy.
Even while ovulating, chances of getting pregnant are approximately around 25%. In anovulation, these chances drop further since the absence of the release of a mature egg/ovum from the female ovaries, makes conception impossible as the fertilization of a mature egg by a sperm cell is impossible.
An anovulatory cycle is difficult to spot as thereis usually still some bleeding.Unless ovulation tracking is done regularly, it may be impossible to know when a woman experiences an anovulatory cycle. Period tracking alone may not be enough to identify this, however, irregularities such as late periods, irregular or absent periods and mid cycle spotting may be signs a woman is experiencing an anovulatory cycle. Anovulatory cycles are also often longer than regular cycles.
Detection of anovulation could be done through series of ultrasounds by a gynecologist/fertility specialist. These ultrasounds confirm whether there is ripening of follicles, the characteristics of the endometrium (lining of the womb), and corpus luteum production. Hormonal assays to check levels of follicle stimulating hormone (FSH), luteinizing hormone (LH), estrogen, progesterone, androgens (male hormones) and prolactin, are also required in anovulation detection.
WHAT ARE SOME OF THE CAUSES OF ANOVULATION AND HOW DO THEY AFFECT PREGNANCY?
OBESITY
Obesity causes infertility, by impairing ovarian follicular development. Obesity affects the regulation of gonadotropin (estrogen) production, causing increased free estrogen levels due to increased conversion of androgens (male hormones) to estrogens in fat tissues. Increased estrogen causes a decrease in gonadotropin-releasing hormone (GnRH) by signaling to the brain to stop its production. This anomaly causes irregular or anovulatory cycles.
Overweight and obese women have a higher incidence of menstrual dysfunction and anovulation.
POLYCYSTIC OVARY SYNDROME
Polycystic ovary syndrome (PCOS) is the most common cause of anovulatory infertility and menstrual cycle abnormalities. This syndrome is characterized by the presence of elevated androgen (male hormone) levels in the blood. The ovaries may develop numerous small collections of fluid (follicles) and fail to regularly release eggs. In addition to the elevated androgen levels, anovulatory women with PCOS have raised serum concentrations of luteinizing hormone (LH), with normal or slightly suppressed serum follicle stimulating hormone (FSH) levels. LH concentrations tend to be higher in anovulatory cycles, due to failure of the signaling mechanism that is normally exerted by cyclical changes in estrogen and, in particular, progesterone. Obesity is associated with PCOS and can worsen complications of the disorder.
LOW BODY WEIGHT, EXCESSIVE EXERCISE AND HIGH STRESS LEVELS.
Low body weight, excessive exercise and high stress levels all lead to a condition termed Functional Hypothalamic Amenorrhea (FHA). This is an anomaly in the release of Gonadotropin-Releasing Hormone (GnRH) from the hypothalamus in the brain, which is supposed to cause the release of Follicle Stimulating Hormone (FSH) which causes growth of ovarian follicles and Luteinizing hormone (LH) which leads to the final maturation of the oocyte and its release from the ovary (ovulation).
In turn, decreased FSH and LH secretion leads to reduced estrogen production in the ovary.
HYPERPROLACTINEMIA
Prolactin is a hormone produced by the pituitary gland in the brain. The most important function of this hormone is to stimulate the production of milk in women after the delivery of a baby. Though prolactin is present in the blood in lower quantities without pregnancy, the levels of the hormone increase during pregnancy and after childbirth. This causes the breasts to enlarge in preparation for breast-feeding and secretion of milk after delivery. High prolactin levels are associated with anovulation through the inhibition of pituitary hormones, mainly through luteinizing hormone (LH) suppression. During the first several months of breastfeeding, the higher prolactin levels also serve to suppress ovarian cycles. This is what causes the cessation of menstrual bleeding for months, after childbirth. An excessive level of prolactin in women who are not pregnant or just went through childbirth, therefore, causes anovulatory infertility through the same mechanism… and anovulation
