Causes of Infertility

There are many causes of infertility and female causes constitute around 60 to 70 % of all cases of infertility, the remainder being male causes or both male and female. To simplify the understanding of the causes it is important to understand how fertilization and conception occurs.

Females are usually born with approximately a million to a million and a half immature eggs or oocytes within the ovaries. After puberty, each month around one to two of those eggs will develop and become prepared for ovulation and possible conception, whilst about three hundred after an initial attempt at development fade away. This is called atresia. The best quality eggs tend to prepare for release (ovulation) in the first two decades after periods commence, so that women tend to be most fertile in their twenties and thirties. As the quality and number of eggs declines in the thirties, so conception becomes more difficult and in the late thirties and early forties higher levels of the pituitary hormone is required to stimulate the eggs, which may not be of best quality so conception falls and miscarriage rate and foetal abnormalities and complications increase.

The process of conception:

STEP 1:
At the beginning of each cycle, one or two eggs begin to develop within a capsule or cystic structure called the follicle. In the first two weeks after the menstrual period the follicle develops in size until prepared for ovulation at around day fourteen to sixteen. The egg is then released and if intercourse has occurred, the egg will be fertilized in the pelvic cavity outside the fallopian tube by the sperm.

STEP 2:
The two cell embryo (male and female components) will be then drawn into the end of the fallopian tube and begin its transit to the uterus. This takes approximately five to seven days and during this time the cells of the embryo commence dividing resulting in an increasing number of cells. By the time that it arrives at the uterus, it should be mature enough for implantation. If there is a kink or blockage in the fallopian tube when the embryo is ready for implantation, implantation will occur here and an ectopic pregnancy will result.

STEP 3:
On arriving at the uterus the embryo attempts to implant in the lining of the uterus (endometrium). This means that the endometrium has to be "primed" i.e. well supplied with blood vessels and nutrients in order for the embryo to imbed and form a proper connection (feto-maternal connection). If the lining of the uterus is either thin or poorly supplied with blood vessels, implantation will not occur (failed implantation), or only "hold" for a short time, followed by the pregnancy breaking away and a pregnancy loss occurring (miscarriage). This implantation process continues up until around 28 weeks of pregnancy or even further and if the process of implantation is affected at any stage in the pregnancy then the connection between the mothers blood supply and the baby can be compromised with resultant poor nourishment of the developing fetus or baby with poor development of different organs, poor growth or increased likelihood of pregnancy loss later on in pregnancy. Implementing a sturdy fetomaternal connection at the very outset i.e. at implantation five days after ovulation is therefore highly important as well as maintaining this connection throughout the pregnancy.

Areas where fertilty chances may be affected:

OVARY AND OVULATION

1) Development of Eggs in the Ovaries: Each month development of a healthy oocyte or oocytes is important for successful conception. In their twenties or thirties many women will develop a very healthy oocyte for between ten and twelve cycles a year. By the time a woman reaches her thirties and forties the number of "good quality" eggs has declined to around five to six per year. Each month only around 25% will successfully come to fruition this means that by the mid to late thirties there is a dramatic reduction in success rate of conception.

2) Number of Eggs: Some women are born with low numbers of primordial follicles or early eggs in the ovaries and therefore the natural process of generation which occurs each cycle can lead to an early loss of eggs of adequate quality to enable a pregnancy. Furthermore there may be an increased rate of degeneration of eggs which normally disappear each month and this lower than average number in the first instance as well as accelerated loss can lead to premature menopause and inability to conceive.

Causes of poor quality ovulation or egg production.

a) PCOS (Polycystic Ovaries): This is one of the most common causes of infertility in women and affects around 70 to 80 % of women with infertility. PCOS is a condition caused by a hormonal imbalance which is thought to be due in part to high levels of insulin and insulin resistance which prevents the development of a follicle and ovulation may not occur. If it does occur the egg quality may be reduced and the embryo will either not implant or only implant for a short time leading to early or late pregnancy loss. The increasing number of women suffering from PCOS is thought to be due to change in dietary factors as well as genetic background. Modern diets tend to be loaded with more carbohydrate and hidden sugars and constitute a higher proportion of snacks which can lead to an increased production of insulin and worsening insulin resistance. As insulin reduces egg quality as well as constricting tiny arteries supplying the lining of the uterus and ovaries the blood supply will be impeded and the implantation process affected even if an ultrasound scan suggests that the lining of the uterus is adequately thickened. To improve ovulation quality and implantation therefore, reducing insulin levels and insulin resistance is key. Tests indicating polycystic ovaries and insulin resistance include a raised LH FSH ratio (pituitary hormones) on day 1- 4 of a cycle, ultrasound scan picture of multiple tiny cysts within the ovaries with or without normally developing follicles, a tendency to put on weight around the abdominal region whether slim or overweight, a tendency to put on weight easily with fluctuating weight, difficulty losing weight, carbohydrate cravings, an abnormal glucose level on a glucose tolerance test, abnormal fasting or two hour insulin levels on a glucose tolerance test, high cholesterol or high blood pressure.

b) Congenital Hormone Disorders (endocrine disorders): Such as hypothyroidism can also cause infertility as it also causes the hormone from the pituitary called prolactin to rise which can suppress ovulation. Patients with underactive thyroid can have other symptoms such as weight gain, fatigue, abnormal menstrual cycles, reduced sex drive, feelings of cold etc.

c) Hyperprolactinemia (High prolactin levels): Can occur spontaneously due to a tiny benign growth within the pituitary. Additionally it can rise with some medications and stress. High levels of prolactin can stop ovulation and hence can stop menstrual periods occurring. This can be diagnosed by a simple blood test and treated with medication if appropriate.

d) Auto immune Causes: Development of antibodies to either the eggs or the embryo (since the embryo is genetically only half belonging to the mother) can be a cause of either poor fertilization, poor implantation or failure of the pregnancy to continue. This is rare, but is more common where other auto antibodies are seen.

e) Failed Ovulation: In some women ovulation appears to occur on their ovulation kits but whilst the LH surge (the hormone indicator of likely ovulation) may occur this does not always mean that the egg can escape and progesterone levels will remain low. This can be corrected with a HCG (human chorionic gonadotropin) injection at around the time the follicle is deemed mature on ultrasound scan.

f) Low Progesterone Levels: If ovulation quality is reduced, the progesterone which is normally produced after release of the egg from the capsule is less and as progesterone is required to support a pregnancy up until the placenta takes over (at around 12 to 14 weeks gestation) this can result in pregnancy loss early on.

FALLOPIAN TUBES

Before it reaches the uterus for implantation the embryo travels along the fallopian tube. During this time there may be a delay or there may be factors which destroy the developing embryo and these are thought to be higher in women with a high proportion of auto antibodies.

1) Infection
Infection with conditions such Chlamydia can cause blockage of the tube and the embryo will either not get through or will start to implant and develop in the tube causing an ectopic pregnancy.

2) Endometriosis
A common cause of infertility is endometriosis occurring in around a third of women with infertility. This is a condition where the lining of cells of the uterus, the endometrium, becomes lost and implanted around the outside of the uterus sometimes in the pelvic cavity, sometimes in the fallopian tube and around the ovaries. As the inner lining of the uterus becomes built up with normal hormones of the cycle so do the endometriosis cells and similarly towards the end of the cycle the cells will shed and attempt to bleed. As the blood cannot escape it becomes trapped in a cystic capsule and small deposits of endometriosis occur. These can set up inflammation processes with scarring and blockage of fallopian tubes. They can also prevent release of the egg and ovulation. Endometriosis deposits are also very toxic to sperm and when endometriosis occurs within the muscle wall of the uterus (adenomyosis) this can also be damaging as it can affect the implantation process.

UTERINE CAUSES

Abnormailities within the lining and wall of the uterus can reduce the chance of implantation as well as the ability of contined pregnancy growth.

1) Previous Traumatic Injury: Women who have had repeated surgical procedures or complications which may affect the uterus or cervix preventing implantation or ability to hold the pregnancy are less common than they were but still a significant factor. This used to be the case where terminations were not conducted by skilled surgeons but are much less common now, although accidents of late pregnancy can still occur.

2) Congenital Defects of the Uterus:Other uncommon causes are congenital defects where the female can be born with abnormal development of the female organs such as absence of one or both fallopian tubes or ovaries, abnormality of the uterine cavity, closure of the uterine cavity etc. Diagnosis is important as occasionally early pregnancy can occur depending upon the nature of the abnormality but failure of either implantation or of the ability of a pregnancy to grow adequately can be explained by this.

MALE FACTOR

Male factor infertility affects around 5 to 10 % of couples with infertility and may be due to reduced quantity or quality of sperm. There are many new treatments available now and the ability to use immature spermatozoa removed directly from the male and injected into the egg has revolutionized the need for a high number of sperm to ensure a pregnancy (sperm retrieval and ICSI).

Appointments available - call us now on 01483 454 016