Overview of Causes of Infertility



Hello, I am Shona Murray. I would like to present an overview of common causes of infertility.

To understand why a couple is having difficulty getting pregnant, it is often easier to first think of what is needed to get pregnant. Simply put we need an egg, a sperm, a way for the egg and sperm to get together to make an embryo and a place for the embryo to grow.

If anything goes wrong with these components we then have infertility.

The egg

First, the egg. A mature egg or oocyte must be developed in the ovary and then ovulated or released from the ovary. For this to happen the brain must give messages to the ovary and the ovary must have eggs or oocytes that can develop in response to these coordinated messages.

If the ovary has no eggs left this results in menopause, when there are fewer than the normal number of eggs left, or only eggs of poor quality remain it results in diminished ovarian reserve. While it is possible to get pregnant with diminished reserve, fertility is markedly decreased. The most common reason for this is advancing age of the woman. Other causes for ovarian failure include prior surgery, chemotherapy or radiation therapy

If the ovary has a normal complement of eggs, but the brain is not giving any messages to develop, no mature eggs are produced. However  the ovary still have a possibility of responding if the messages are given by either medication or the brain starts giving the correct messages again. This condition is know as hypothalmic amenonorrhea. This may result from excessive exercise or stress.

If the hormonal messages that coordinate the growth of the egg are not delivered properly, this will result in failure to ovulate. This is often caused by an underlying hormonal condition such as Polycystic Ovary Syndrome (PCOS), thyroid disease or elevated prolactin levels. Often when the underlying hormonal condition is treated ovulation will resume. If there is no underlying cause for the ovulation problem, medication can be given to induce ovulation.

We test ovarian reserve and ovulation with blood work and ultrasound.

The sperm

Next the male partner must have sperm. We test for male factor infertility by doing a semen analysis. We look at the volume of semen, the sperm count, the motility or number moving, and the morphology or shape of the sperm. An average sperm count is over 20 million motile or moving sperm per ejaculate. As sperm counts drop it gets increasing difficult to father a pregnancy. Causes of low sperm count include exposure to toxins including chemotherapy, radiation, organic chemicals, and many other environmental toxins including extremes of heat. Structural abnormalities, previous cancer,  injury or surgery of the genital region can also cause low sperm count.

Sexual dysfunction including difficulty with erection or ejaculation  can lead to male factor infertility.

The egg and sperm together

Next we must look at how the egg and sperm are getting together. The couple must be having vaginal intercourse close to the time of ovulation. Intercourse at an interval of 1-2 days prior to ovulation is ideal.

The cervix must be open and ideally be able to produce cervical mucous.Prior cone biopsy or LEEP procedure of the cervix may interfere with the sperm being able to get to the egg.

Patent or open Fallopian tubes are essential for the egg and sperm to get together for fertilization. Any inflammation of the Fallopian tube can result in blockage or scarring. This can result in either the sperm and egg not getting together or result in the embryo getting stuck in the Fallopian tube which can result in an ectopic or tubal pregnancy. The most common cause of Fallopian tube damage is prior infection typically with gonorrhea or chlamydia. Prior tubal surgery or endometriosis can effect the ability of the Fallopian tube to work normally.

Fallopian tubes can be evaluated by an X-ray, called HSG, a specialized ultrasound, or by a laparoscopy, surgery that allows us to see the fallopian tubes.

The implantation

Finally we must consider where the embryo needs to implant. The inside of the uterus , the endometrial cavity must be normal. Any growths or scarring within the cavity make it difficulty for the embryo to implant. Issues with the endometrial cavity include uterine polyps, fibroids, or scarring from previous surgery. Fibroids growing in the wall of the uterus may also decrease fertility.

The uterus can be evaluated by HSG, specialized ultrasound or hysteroscopy, a surgery that looks inside the uterus.

With these causes of infertility in mind, an infertility evaluation will be undertaken. Treatment will depend of the results of the evaluation.

Thank you.