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Female reproductive system: conception, anatomy & function

The anatomy of fertility

Before looking at possible causes of infertility, you may like to check some facts about the key organs involved in reproduction.

Vagina: The opening through which sperm travels in order to reach an egg. The vagina also serves as a passage for menstrual flow and secretions, which may help or obstruct sperm from fertilizing an egg.
Cervix: The cervix or neck of the uterus is the lower, narrow portion of the uterus where it joins with the top end of the vagina.
Uterus: A pear-shaped organ also known as the womb. The inner lining of the uterus is called the endometrium. An egg that has been fertilized will implant itself into the endometrium lining and will continue to develop in the uterus throughout pregnancy.
Ovaries: Almond-sized organs located on either side of the uterus, which produce and release mature egg cells. Egg cells develop in follicles - fluid filled sacs in the ovaries. Each month a new egg matures and travels to the fallopian tube. Ovaries also release the hormones oestrogen and progesterone, which are vital for reproduction.
Fallopian tubes: Two ten-centimetre-long tubes, which connect with the uterus. During ovulation, the mature egg passes from the ovaries into the fallopian tube, where fertilization may occur.

Achieving pregnancy depends on the successful interaction of hormones during the menstrual cycle. Some hormones are produced in the ovaries. Others come from two glands in the brain.

A reminder of the basics

During a normal 28-day reproductive cycle, a woman’s body releases a single egg from a follicle in one of her ovaries. The egg travels down one of two fallopian tubes, where it can be fertilized by a man’s sperm. If the sperm reaches and penetrates the egg, a new life begins. As the first few cells divide, the embryo travels to the uterus where it implants and begins to develop into a fetus. If fertilization doesn’t take place, or if for some reason the embryo is unable to implant, the period begins and the cycle starts over. Discover the complex process of conception.

If you have been trying to get pregnant for more than six months and are 35 or older, do not wait to seek medical advice.¹ Find out more about the medical conditions that affect fertility.

Could I be the problem?

Be wary of blame. Almost one in ten couples have difficulties conceiving², but infertility is just as likely to be down to your partner’s health as your own. Male infertility is the primary diagnosis in approximately 25% of cases and contributes to a further 15–25% of the remaining cases.³ It is important that both partners are thoroughly investigated to determine the right course of action.

Ovulation disorders

The normal ovarian cycle is so complex that even small changes may disrupt the cycle and prevent ovulation. In most cases, problems are caused by a hormonal imbalance: the body may not produce enough of a particular hormone or may fail to release a hormone at the right time. Ovulation may also be thrown off by significant changes in weight, either lost or gained.

Fallopian tube disorder

Damage to the fallopian tubes can prevent the sperm and egg fusing. Reasons may include:

Inflammation in the region
A previous ectopic or tubal pregnancy
Scarring caused by surgery
Anatomical changes caused by endometriosis.

Endometriosis

Endometriosis occurs when cells that normally line the uterine cavity grow in areas outside the uterus, for example in the fallopian tubes, ovaries, or even the bladder or intestines, creating an adverse environment in these unsuitable organs. Its cause is largely unknown.

Changes to the uterus or cervix

Sperm may fail to reach the egg if scarring caused by surgery, blockage or inflammation, reduces access to the cervix. A myoma or fibroid (a benign tumour in the uterus) may be the cause of persistent fertility problems or miscarriage.

Reproductive malformations

In very rare cases, conception difficulties are caused by congenital irregularities with the reproductive system that could affect the shape and side of the uterus, the fallopian tubes, the vagina or a combination of these.

Polycystic Ovarian Syndrome (PCOS)

Multiple cysts form in the ovaries. In most cases, this disorder is associated with a high level of male hormones and ovulation disorders.

Immune system disorders

On rare occasions, an impaired immune system may treat the egg or sperm as a ‘foreign body,’ and attack it as an ‘intruder.’

Personal lifestyle can also affect fertility. Being overweight, unhealthy eating habits or stress can also play a role. Learn about simple lifestyle changes that could increase your chances of becoming pregnant.

^{1. Definitions of fertility and recurrent pregnancy loss. Fertil Steril 2008; 90:S60. 2. Boivin J et al, International estimates of infertility prevalence and treatment seeking: potential need and demand for infertility medical care. Hum Reprod. 2007;22: 1506-1512. 3. Collins J.A. Evidence-based infertility: evaluation of the female partner. International Congress Series 2004; 1266: 57–62.}

Vagina

The muscular opening through which sperm travels in order to reach an egg. The vagina also serves as a passage for menstrual flow and secretions, which may assist or obstruct sperm in their journey to fertilizing an egg.

Varicocele

The presence of varicose veins around the testicles caused by poor circulation. The increase in blood leads to a rise in the temperature in the testicles. This causes abnormal testosterone levels, which hinder the production of sperm.

Vas deferens

A long curving tube that forms part of the sperm storage and transport system.

Urologist

A medical specialist dealing with the treatment of the urinary tract and urogenital system.

Uterus

A pear-shaped organ also known as the womb that supports the developing foetus throughout pregnancy. The uterus consists of: the cervical opening, the cervix and the uterine cavity. The two fallopian tubes open into the uterus.

Ultrasound

A medical imaging technique used instead of X-rays to view the reproductive organs and monitor the development of follicles.

Testicles or testes

The male sex glands, which are located in a sac below the penis called the scrotum. Their main functions are to produce sperm and to release the male sex hormone testosterone. In order to produce and nurture sperm, the temperature within the testicles remains around 1°C cooler than normal body temperature.

Testicular cancer

A malignant tumour that develops in the testicle may destroy testicular tissue. If not detected early enough it may also spread to other parts of the body.

Testicular Sperm Extraction

The extraction of sperm directly from the testicles (TESE) or from the epididymis (MESA) if sperm is not found in the ejaculate. A minor surgical procedure is carried out to remove tissue samples that may contain sperm. The sperm is then used in Intracytoplasmic Sperm Injection (ICSI) treatment.

Testosterone

The male hormone responsible for forming secondary sex characteristics, such as facial hair, and supporting the sex drive. Testosterone is also necessary for sperm development.

Tubal pregnancy

The development and attachment of an embryo in a fallopian tube. See also ectopic pregnancy.

Pelvic Inflammatory Disease

A generic term for inflammation of the uterus, fallopian tubes and/or the ovaries, which may lead to scarring or adhesions to nearby tissues. PID can refer to viral, fungal, parasitic or bacterial infections and is often associated with sexually transmitted infections.

Penis

The male organ that delivers semen, containing sperm, into the vagina on ejaculation. During sexual stimulation, the penis becomes erect as its spongy tissue fills with blood.

Pituitary gland

The pituitary gland controls the function of other endocrine glands and is located at the base of the brain. It produces hormones including Luteinizing Hormone (LH) and Follicle Stimulating Hormone (FSH), which stimulate the ovaries and testicles.

Placenta

A temporary organ through which the mother nourishes the developing foetus, transfers oxygen and receives carbon dioxide waste from the foetus. After birth, the placenta detaches from the uterine wall and is expelled from the body as afterbirth.

Premature Menopause or Premature Ovarian Failure

Menopause that occurs at or before the age of 40, resulting from genetics, autoimmune disorders, medical procedures or treatments.

Polycystic Ovarian Syndrome (PCOS)

A hormonal imbalance that leads to the formation of ovarian cysts and disrupts ovulation. Without progesterone, a woman's menstrual cycle is irregular or absent.

Progesterone

A hormone secreted by the corpus luteum to prepare the body for pregnancy and, if pregnancy occurs, for maintaining it until birth via the placenta. If implantation does not occur, hormone levels drop, the endometrium breaks down and menstruation occurs.

Prolactin

A hormone produced in the brain, which stimulates lactation - the flow of breast milk.

Prostate gland

In men, a chestnut-sized gland below the bladder, which produces 60% of the seminal fluid used to transport sperm.

Puberty

The stage of adolescence marked by the development of secondary sex characteristics, including menstruation in females. In girls, puberty occurs between the ages of about 11 and 14, and between 13 and 16 in boys.

Obstetrician/Gynaecologist

A doctor who delivers babies and specialises in the treatment of female reproductive organs.

Oestrogen

A hormone that stimulates secondary female sexual characteristics and controls the course of the menstrual cycle. Oestrogen is also produced in low quantities in males.

Oligospermia

A condition when a sperm sample contains less than 20 million spermatozoa per ejaculate. Many medical conditions reduce sperm concentration. The effects may be temporary or permanent. See also Azoospermia.

Outpatient

A Person undergoing a clinical procedure that does not require admission to hospital.

Ovarian failure

The failure of the ovary to respond to hormonal stimulation from the pituitary gland because of damage to or malformation of the ovary, or a chronic disease such as autoimmune disease or ageing process.

Ovarian follicle

The structure in which eggs are nurtured to maturation. Although in general only one egg is released at a time, somewhere between 10 and 20 follicles begin the process of maturation monthly. The excess ovarian follicles are reabsorbed before ovulation occurs.

Ovulation

The release of the matured egg or ovum from the ovarian follicle.

Ovum

A matured egg.

Ovulation Induction (OI)

Medical treatment carried out to initiate ovulation.

Ovarian Hyper Stimulation Syndrome

A condition characterised by enlargement of the ovaries, fluid-retention and weight gain. May occur when the ovaries are over-stimulated during assisted reproduction.

Ovaries, Ovary

Almond-sized organ(s) located on either side of the uterus, which produce and release mature egg cells and the hormones oestrogen and progesterone.

Manual palpation

A physical examination for any genital abnormalities or any other physical signs that might be associated with conception difficulties.

Myoma

A benign tumour in the uterus consisting of muscle tissue. Myomas are often the cause of persistent infertility or miscarriage.

Micromanipulation

A variety of techniques performed in a laboratory with microscopic guidance, such as Intracytoplasmic Sperm Injection (ICSI).

Menopause

Typically diagnosed 12 months after a woman’s last menstrual cycle. Natural menopause occurs when the ovaries begin decreasing their production of the sex hormones oestrogen and progesterone and marks the end of a woman’s fertility. See premature menopause.

Menstruation or menses

Shedding of the uterine lining by bleeding. In the absence of pregnancy, this normally occurs about once every 28 days.

Miscarriage

Spontaneous loss of a viable embryo or foetus from the uterus.

Motility

The ability of sperm to swim or move. Poor motility means sperm have less chance reaching and fertilizing the egg.

Multiple pregnancy

A pregnancy with two or more foetuses.

Mumps

A viral disease of the parotid (salivary) glands. Contraction of the virus after puberty may damage sperm-producing cells in the testicles. In most cases, only one testicle is affected. Some men could suffer permanent sterility.

Idiopathic infertility

Unexplained infertility.

Infertility or primary infertility

The inability of a couple to achieve conception after a year of unprotected intercourse – six months if the woman is over 35 – or the inability to carry a pregnancy to live birth. Also see Subfertility.

Intracytoplasmic Sperm Injection (ICSI)

A single sperm is injected directly into an egg cell with microscopic guidance. If fusion takes place, the embryo is transferred into the uterus for implantation. This clinical procedure is often used in conjunction with In Vitro Fertilisation if the male partner has a very low sperm count, low sperm motility or poor-quality sperm.

Intrauterine device

(IUD): A contraceptive device consisting of a small piece of bent plastic, which prevents pregnancy by changing the environment of the uterus.

Intrauterine Insemination (IUI)

A procedure whereby sperm are deposited directly into the uterus via the cervix using a catheter.

Irregular ovulation

Menstrual cycles that vary more than a few days in length from month to month are considered irregular. Most menstrual cycles occur about every four weeks, with the normal range lasting between 24 and 35 days.

In Vivo

A process that occurs inside the body.

In Vitro Fertilization (IVF)

Eggs produced with the assistance of fertility drugs are retrieved from the woman’s body and fertilized by sperm in a laboratory environment. The resulting embryos are transferred via catheter to the uterus.

Immune system disorders

On rare occasions, an impaired immune system may regard the egg or sperm as a ‘foreign body,’ and attack it as an ‘intruder.’

Implantation

The process whereby the embryo embeds itself into the lining of the uterus. The cells from the embryo eventually connect with the mother’s blood vessels to form the placenta. See also ectopic pregnancy.

Hepatitis

A disease characterised by inflammation of the liver arising from various causes including a range of viruses (i.e. A, B, C, E).

Human Immunodeficiency Virus (HIV)/Acquired Immune Deficiency Syndrome

A disease of the human immune system caused by the HIV virus, which can be contracted through sexual contact.

Hormonal imbalance

An abnormal hormonal balance, which may arise for example, from a deficiency or excess of oestrogen or progesterone.

Hormones

Chemical messengers produced by the body that transmit instructions from one organ to another.

Human Chorionic Gonadotrophin

A hormone released by the placenta after implantation that keeps the corpus luteum producing estradiol and progesterone, and thus preventing menstruation. The hormone is also given via injection to trigger ovulation after some fertility treatments. In men, it is used to stimulate testosterone production.

Human menopausal gonadotrophin

Natural compounds found in the urine of postmenopausal women. Once extracted and sterilised, hMG is given to women to stimulate ovulation.

Hysteroscopy

A visual examination of the uterus via the vagina using a telescopic instrument, to identify any malformations in the uterus lining, the presence of myomas, fibroid growths or damage to the fallopian tubes. If necessary, minor surgery may be performed at the same time without the need for a large incision.

Hypogonadotrophic Hypogonadism

Impaired activity of the hypothalamus or pituitary glands resulting in below-average function of the ovaries or testicles and low in low production of the hormones Luteinizing Hormone (LH) and Follicle Stimulating Hormone (FSH), Oestrogen, Progesterone and Testosterone, which are necessary for reproduction.

Hypothalamus

The gland at the base of the brain that controls the release of hormones from the pituitary glands.

Fallopian tube

A funnel-shaped passage through which sperm are guided towards the egg, and fertilized eggs are conveyed to the uterine cavity.

Fertilization

The moment of conception when the genetic material contained in the sperm and egg combine to create an embryo. Fertilization usually occurs inside the fallopian tube. It may also occur in vitro during a clinical process. See also In Vitro Fertilization.

Fertility treatment

Any procedure used to enhance fertility or to help couples achieve pregnancy.

Fertility psychologist

A health specialist with professional qualifications in psychology and counselling relating to fertility issues.

Fibroid tumour

A benign (that is, not malignant or life-threatening) tumour made up of fibrous tissue that may form in the uterine wall. Fibroid tumours may be present without any symptoms, or may cause abnormal menstrual patterns or infertility.

Follicle

A fluid-filled sac in the ovary, which contains the egg released during ovulation. Each month a new egg matures and travels to the fallopian tube.

Follicle Stimulating Hormone

A hormone released by the pituitary gland in both sexes. In women, FSH stimulates the growth of the ovarian follicle necessary for egg production. In men, FSH stimulates and supports sperm production. Elevated FSH levels are associated with gonadotrophin failure in both men and women.

Freezing

(See Cryopreservation)

Ectopic pregnancy

A pregnancy in which the embryo implants outside the uterus and cannot be sustained.

Ejaculate

The seminal fluid discharged upon male orgasm, which helps transport sperm.

Egg retrieval

A procedure used to obtain eggs from ovarian follicles for use in In Vitro Fertilization. Retrieval may be performed during a laparoscopy procedure or via the vagina using a blunt syringe and with the aid of an ultrasound to locate the follicle in the ovary.

Embryo

The early stages of foetal growth from conception to the eighth week of pregnancy.

Embryo transfer

The process whereby an embryo is transferred into the uterus after the egg has been fertilized outside the body during a laboratory procedure.

Embryologist

A specialist involved in the various aspects of assisted reproduction laboratory procedures related to sperm, oocytes and embryos.

Endocrinologist

A medical specialist concerned with the study of hormones and infertility, having first trained as an obstetrician/gynaecologist.

Endometrial biopsy

The removal of a sample of the lining of the uterus for examination.

Endometriosis

A condition whereby cells that normally line the uterine cavity grow outside the womb, for example in the fallopian tubes, ovaries, or even the bladder or intestines. The cause is largely unknown. Scarring from endometriosis may cause conception difficulties.

Endometrium

The lining of the uterus, which is shed during the menstrual cycle. If conception takes place, the embryo implants itself into the rich vascular membrane, which nourishes the developing foetus.

Epididymis

A tightly coiled tube located above the testicles or testes, where sperm mature for fertilization.

Cervical mucus

A natural lubricant produced by the female body that aids the transportation of sperm and helps protect against infection.

Cervix

The cervix or neck of the uterus is the lower, narrow portion of the uterus where it joins with the top end of the vagina.

Chlamydia

A sexually-transmitted infection, which may be asymptomatic or cause genital inflammation and discharge, pelvic pain and fever. Untreated, chlamydia can lead to Pelvic Inflammatory Disease (PID) and fertility problems.

Chromosomes

Structures found in the nucleus of cells that contain genes and carry heredity information, such as eye colour, blood type and vulnerability to disease. Humans have 23 pairs of chromosomes. One set of 23 chromosomes is inherited from the biological mother via her egg and the other from the biological father, via his sperm. Each sperm cell contains either male or female sex chromosomes. As such, it determines the gender of the foetus. Genetic abnormalities occur when an individual is born missing a chromosome or has more copies of a chromosomal pair.

Clomiphene citrate

A prescription drug used to bring on ovulation. It comes as a tablet and is often used as an initial treatment for women with ovulation problems. Clomiphene citrate induces ovulation in 80% of women who have trouble ovulating on their own.

Conception

The moment of fertilization when the sperm meets and penetrates the egg.

Congenital abnormalities

Physical abnormalities present at birth.

Corpus luteum

A hormone-secreting mass within the ovary that forms from the remains of a follicle each time an egg is released. The hormones it produces prepare the uterus for embryo implantation. If pregnancy does not occur, the mass is shed during menstruation.

Cryopreservation

A technique used to store human tissue at very low temperatures. Embryos that are not used in an ART cycle may be preserved in this way for future use. Also known as “Freezing”.

Cryptorchidism

A condition usually detected at birth or childhood whereby the testicles fail to descend. When a male foetus develops in the uterus, his testicles normally form inside his abdomen and descend into the scrotum shortly before birth. Undescended testicles usually descend themselves by the sixth month of life, but are unlikely to descend after this period of their own accord.

Basal body temperature

The lowest temperature attained by the body, usually measured immediately after awakening and before any physical activity is undertaken. A rise in body temperature of about half a degree about 14 days into an average 28-day cycle suggests ovulation has taken place.

Biopsy

The removal of a small portion of body tissue for microscopic examination.

Biosynthesis

A process where chemical compounds are made in the body from simpler compounds or smaller molecules.

Bladder

The organ that collects urine excreted by the kidneys prior to disposal by urination.

Blastocyst transfer

A procedure whereby an embryo is left to develop for about 5 or 6 days to reach the ‘blastocyst stage’ before being transferred into the uterus for implantation.