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Fertility » Causes of female infertility

 

Causes of female infertility

When a couple is unable to conceive it is necessary to find out the underlying causes of infertility. An accurate diagnosis will allow the specialist to choose the best treatment plan based on the patient´s individual needs and to evaluate the chances of success in each particular case.

The investigations carried out on the couple aim to detect disorders or abnormalities that may lead to infertility and sterility. In 40% of the cases the cause is identified only in the female, in another 40% the cause is identified only in the male and in 20% of cases causes can be detected in both partners. However in 15% of the couples the underlying cause of infertility cannot be detected by the current diagnostic methods. Luckily the percentage of cases with unexplained infertility is decreasing.

Some couples are unable to conceive – i.e. when there is a tubal blockage or an azoospermia) while others just have a lower reproductive function caused by mild abnormalities.

1. OVARIAN

Age

Fertility decreases with advancing female age.

Women are born with a limited number of eggs in their ovaries. These eggs will be used throughout their life until they reach 50 years old, when 80% of women have run out of eggs and menopause occurs. However 10-15 years prior to menopause there is a significant decrease in the number and quality of the eggs. The risk of having eggs with chromosomal abnormalities rises and even if they are successfully fertilized they will produce embryos less capable of implanting and/or will increase the miscarriage rate. This leads to a gradual decline of woman´s fertility despite having regular menstrual cycles and ovulations.

Several tests may be useful in assessing a woman´s ovarian reserve and thus her fertility potential and her chances to conceive. These tests typically include an ultrasound and a hormonal check-up.

Primary ovarian failure

It includes several disorders where the ovaries fail to produce and develop eggs. Premature ovarian failure is generally associated with an abnormal karyotype, i.e. alterations in the number or structure of chromosomes such as in Turner´s, Swayer´s or Savage´s syndrome.

Investigations carried out to detect this condition typically include a karyotype and a hormonal check-up. Ultrasounds and laparoscopies are also used to diagnose this condition.

Premature ovarian failure

It is defined as an ovarian failure before the age of 40. Some of the causes include hereditary diseases, enzyme alterations, infections, autoimmune disorders or endometriosis which damages wide areas of healthy ovarian tissue.

Chemotherapy, radiotherapy, surgical removal of the ovaries or even smoking may lead to a premature ovarian failure and thus to premature menopause.

Annovulation

When the ovaries do not release eggs to the tubes there is no possibility of conceiving spontaneously. Annovulation occurs when there are alterations in the levels of hormones produced by the ovaries (estradiol, progesterone), by the hypothalamus and the pituitary gland (GnRH, FSH, LH, prolactin, etc.) and by the thyroids (TSH). Other causes of annovulation are a low ovarian reserve or endometriosis in the ovaries.

One of the most common disorders associated with annovulation is the polycystic ovarian syndrome.

The main method for detecting ovulation is a simple blood test to check the progesterone levels.

Hormonal check-ups and ultrasounds will allow the healthcare provider determine the causes of annovulation.

Polycystic ovaries

Polycystic ovaries are one of the most common causes of infertility and annovulation.
Women with polycystic ovaries have many small follicles in the ovaries and often abnormal FSH and LH levels. They may also present high levels of androgens and glucose and insulin metabolism disorders.

This disorder is frequently associated with irregular periods but no external signs to more severe forms involving lack of periods, enlarged ovaries, excessive hair growth, acne and overweight. We talk about polycystic ovarian syndrome when a woman presents any of these conditions.

The polycystic ovarian syndrome can be detected with an ultrasound examination and a hormonal check-up.

Endometriosis

Endometriosis occurs when the endometrium (inner layer of the uterus) grows outside the uterus in form of patches that may grow and form cysts.

Endometriosis may lead to a loss of healthy ovarian tissue and therefore a decrease in the ovarian reserve.  This condition may also have an impact on the ovulation and the egg quality. Endometriosis may spread gradually and damage the whole ovarian tissue.

Although endometriosis can be detected with an ultrasound examination, the only definite way to make an accurate diagnosis is by a laparoscopy which allows the surgeon to look inside and remove patches of endometriosis and endometrial cysts. Endometriosis can also be detected during in-vitro fertilization by evaluating the fluid in the follicles.

Egg abnormalities

Other causes of infertility or sterility are genetic or chromosomal abnormalities and alterations in the structure or functionality of the eggs.

Some women that are carriers of chromosomal alterations do not have any health problems or abnormal external signs. Despite having a well-kept ovarian function a large number of eggs are not capable to produce a healthy embryo.

In some cases it may not be possible to detect structural, biochemical or functional disorders in the eggs which may reduce their chances to be fertilized and produce embryos

A karyotype is used to detect chromosomal disorders on both partners. In an in-vitro fertilization cycle it is possible to visualize the eggs appearance, their interaction with the sperm (fertilization) and the development of the embryos. The Preimplantation Genetic Diagnosis (PGD) associated with IVF enable doctors to screen the embryos for chromosomal or genetic abnormalities.

2. TUBAL ABNORMALITIES

Tubal abnormalities

Tubal damage may stop the ability of the tubes to pick up the eggs, prevent the sperm from reaching the egg and transport the embryos. This will reduce the chances to achieve a pregnancy or prevent this from occurring, depending on how severe the tubal damage is.

Common causes of tubal damage include endometriosis, hydrosalpinx (fluid filled Fallopian tube), infections, scars from previous surgeries. Sometimes the reason is unknown. In some cases the tubes have been surgically removed (salpingectomy) due to a tumor or a previous ectopic pregnancy.
The blockage of the tubes is a relevant pathology leading to infertility. If only one tube is blocked we will consider this a subfertility condition as the tube will be unable to properly pick up and transport the egg when ovulation occurs from its side.

A hysterosalpingogram (HSG) is the most common method to detect tubal blockages.

3. UTERINE PROBLEMS

Uterine problems

There are several disorders that may turn the uterus into a hostile environment for a pregnancy.

Among these we can find congenital uterine malformations, such as a uterine septum or a bicornuate uterus and other problems linked to its shape, to fibroids, polyps or intrauterine adhesions. All these factors may reduce the endometrial receptivity.

The transport and preparation of the sperm through the cervix may also be affected. Common causes include hormonal, infectious, immunological or surgical (curettages and conization) factors.

Investigations to check for uterine abnormalities typically include an ultrasound, a hysterosalpingogram and a laparoscopy and hysteroscopy.

4. DIAGNOSIS

Diagnosis

The process by which a woman gets pregnant and delivers a baby is extremely complex. That is the reason why it is absolutely necessary to undertake a wide range of tests to find out the causes of sterility or infertility.

The application and assessment of these techniques require the cooperation and coordination of an experienced and well-trained team.

In this section we will describe the most common tests for infertility evaluation and explain why they are carried out and the implications for the diagnosis.

With these test results we are able to detect the causes of infertility and make a treatment plan. In some cases it may be necessary to conduct further investigations to evaluate the situation in greater depth.

Transvaginal ultrasound

Transvaginal ultrasounds play an important role in the diagnosis and treatment of infertility. It is a safe and non –invasive method that enables us to look inside the body as many times as needed.

It is particularly helpful in fertility treatments as it gives us a clear view of the uterus and both ovaries and allows us to determine the number of antral follicles during the first days of a woman´s cycle and her ovarian reserve.

It also enables us to track the growth of the follicles in patients going through an ovarian stimulation. Inseminations, egg collections and embryo transfers are performed under ultrasound guidance.

Hysterosalpingogram (HSG)

The hysterosapingogram (HSG) is an X-ray of the uterus and fallopian tubes. This test allows us to evaluate the shape of the uterus and any damage or blockages of the fallopian tubes and detect polyps and other abnormalities in the uterus. The HSG belongs to the first round of tests to detect infertility and sterility problems. This test is strongly recommended prior to those fertility treatments that require a good tubal function, i.e. artificial insemination or ovulation induction with scheduled intercourse.

Hysteroscopy

The hysteroscopy is a medical procedure to evaluate the uterine cavity and the endocervical canal.

This test can help detect abnormalities inside the uterus such as:
•    Polyps
•    Fibroids
•    Adhesions
•    septate uterus, etc.

During this test a narrow instrument with a light attached to it known as a hysteroscope is placed through the cervix allowing the doctor to examine all the way up to the uterus and the endometrial cavity.

In some cases an operative hysteroscopy may be required on an outpatient basis in which instruments are passed through the hysteroscope to treat any abnormalities found in the uterus.

Laparoscopy

A laparoscopy is a surgical procedure that enables us to have a comprehensive view of the outer surface of the uterus, fallopian tubes, ovaries and pelvic cavity and detect morphological abnormalities and other disorders such as endometriosis and adhesions. It also helps us to detect blockages of the fallopian tubes.

During a diagnostic laparoscopy a small flexible tube known as a laparoscope with a light source and a camera attached to it is inserted through a small incision just below the navel. The camera relays images of the abdomen and pelvis.  A small amount of carbon dioxide gas is pumped into the abdomen in order to expand the cavity.

The laparoscopy is minimally invasive, but you should stay at the clinic for a few hours after surgery before you can leave the clinic. This procedure is carried out under general anesthesia.

Surgical laparoscopies are often used to treat some abnormalities detected during the procedure, i.e. removing of adhesions, cysts, fibroids, endometriosis, etc. The recovery time is longer compared to a diagnostic laparoscopy.

Karyotype

A karyotype is a test to examine the number and structure of chromosomes in a sample of cells. Each cell must have a total of 46 chromosomes divided into 22 autosome matching pairs and two sex chromosomes. The latter determine the sex of the baby. The karyotyping is done as a blood test.

Carriers of defective chromosomes often have fertility problems due to a low production or abnormal structural changes of the gametes.

Karyotype tests are strongly recommended in couples with fertility problems, especially if they have had recurrent miscarriages or several implantation failures.

Hormonal check-up

Blood tests to determine the levels of hormones in blood may be particularly helpful to detect:

• Menstrual disorders
• Presence or absence of ovulation
• Complete the study of polycystic ovaries
• Imbalance in the prolactin levels
• Unexplained ovarian failure
• Ovarian reserve and potential response to an ovarian stimulation.

A blood fertility testing typically includes the FSH, LH, estradiol, progesterone, androgens, prolactin, inhibin B, AMH, etc.