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A complex process: how pregnancy occurs

A complex process

For most couples, expectations of a successful pregnancy are realised even if a little help is needed along the way. Pregnancy is a result of a complex combination of factors and events and complications can occur at any step along the way.

During a normal 28-day reproductive cycle, a woman’s body releases a single egg from a follicle from one of her ovaries.
The egg travels down one of two fallopian tubes, where it can be fertilized by sperm – which can survive for 48 to 72 hours within the female body.
If the sperm reaches and penetrates the egg and the couple’s genes combine to create an embryo, a new life begins.
As the first few cells divide, the embryo travels to the uterus where it implants into the lining or endometrium, and begins to develop into an embryo.
If fertilization doesn’t take place, or if for some reason the embryo is unable to implant, the uterus lining is expelled from the body, leading to menstrual bleeding (the period), and the cycle starts over.

The best time to conceive is during the “fertile window” – that is, during the 6-day interval ending on the day of ovulation.¹ Use the ovulation calculator to help determine your fertility peak.

The role of hormones

Hormones regulate the male reproduction system and sperm production. In women, they control the menstrual cycle, the development and release of the egg and help prepare the uterus to receive an embryo.

When to think about getting medical advice

Becoming pregnant is a complicated process and it’s not uncommon for difficulties to arise. About one in ten couples need medical advice or help.² For most, there are solutions.

Doctors recommend that couples seek help if a woman fails to become pregnant:

After twelve months of unprotected intercourse – six months if the woman is over the age of 35.³
If a woman has had two or more miscarriages.³
If certain medical conditions affect your chances.

Fertility declines with age. For a healthy woman, the chances of becoming pregnant in a given month is about 20% at the age of 30 and only 5% at the age of 40.⁴ If you have been trying to get pregnant for six months and you are 35 or older, do not wait to seek medical advice.³

^{1. Optimizing Natural Fertility. Fertil Steril 2008;90:S1-6. 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. Definitions of fertility and recurrent pregnancy loss. Fertil Steril 2008;90:S60. 4. Age and Fertility. A Guide for Patients. ASRM 2003; http://www.asrm.org/Patients/patientbooklets/agefertility.pdf}

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.

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.

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.