Infertility

How conception works and where it can fail

Pregnancy requires several steps to go right: an egg must be released (ovulation), sperm must reach it through the cervix, uterus and fallopian tube, fertilization must occur in the tube, and the embryo must travel to the uterus and implant in a receptive lining. Infertility occurs when one or more steps fail.

For signs to look out for and when to seek help, see trouble getting pregnant.

Causes of infertility

Roughly a third of cases involve female factors alone, a third male factors alone, and the rest both partners or no identifiable cause.

Ovulation disorders

The most common treatable female cause.

• Polycystic ovary syndrome (PCOS): irregular ovulation with high androgens and/or polycystic ovaries on ultrasound.
• Hypothalamic amenorrhea: low weight, intense exercise or stress switches off the brain signals for ovulation.
• High prolactin from a pituitary adenoma or medicines.
• Thyroid disease.
• Premature ovarian insufficiency: loss of ovarian function before 40.

Tubal and pelvic factors

• Blocked or damaged fallopian tubes from pelvic inflammatory disease (often chlamydia), previous ectopic pregnancy or surgery
• Hydrosalpinx, a fluid-filled blocked tube that also lowers IVF success
• Endometriosis, which distorts pelvic anatomy and impairs egg and embryo quality
• Pelvic adhesions

Uterine and cervical factors

Uterine fibroids that distort the cavity, endometrial polyps, scarring inside the uterus (Asherman syndrome), a septum or other congenital differences, and occasionally cervical problems.

Age

Egg number and quality decline with age, and the proportion of eggs with chromosome errors rises steeply from the mid-30s. This lowers conception rates and raises miscarriage risk.

Male factors

• Low sperm count (oligospermia), no sperm (azoospermia), poor motility or abnormal shape
• Varicocele, enlarged veins around the testis
• Hormonal problems, including suppression from anabolic steroids or testosterone use
• Genetic causes such as Klinefelter syndrome and Y-chromosome microdeletions
• Blockages from infection, vasectomy or congenital absence of the vas deferens (linked to cystic fibrosis genes)
• Erectile and ejaculatory dysfunction
• Past undescended testes, mumps orchitis, chemotherapy or radiation

See male factor infertility.

Unexplained infertility

Diagnosed when standard tests are normal. It is common and has reasonable outcomes with treatment.

Fertility tests

For women

For men

• Semen analysis: volume, count, motility and shape. An abnormal result is repeated, ideally after about 3 months, because sperm production takes roughly 74 days.
• Hormone tests (testosterone, FSH, LH) if the count is low.
• Genetic tests for very low counts or no sperm.
• Scrotal ultrasound for varicocele or blockage.

Treatment

Lifestyle

Reaching a healthy weight (even 5% to 10% weight loss restores ovulation in many women with PCOS), stopping smoking, limiting alcohol, stopping anabolic steroids, and treating thyroid disease or diabetes.

Ovulation induction

• Letrozole: the first-line tablet for ovulation induction in PCOS, with higher live birth rates than clomiphene.
• Clomiphene citrate: an alternative oral medicine.
• Gonadotropin injections: for women who do not respond to tablets or have hypothalamic causes.
• Metformin may help some women with PCOS and insulin resistance.

Ovulation induction carries a higher risk of twins and needs ultrasound monitoring.

Surgery

Removing polyps, fibroids that distort the cavity, uterine septum or scar tissue; treating endometriosis; removing or blocking a hydrosalpinx before IVF; repairing varicoceles or blocked male ducts in selected men.

Intrauterine insemination (IUI)

Washed sperm is placed directly in the uterus around ovulation, often with mild ovarian stimulation. It is used for mild male factor, unexplained infertility, and with donor sperm.

In vitro fertilization (IVF)

The ovaries are stimulated to produce several eggs, which are collected and fertilized in the lab. One embryo is usually transferred to the uterus, and others are frozen. ICSI (intracytoplasmic sperm injection) injects a single sperm into each egg and is used for significant male factor. Success depends heavily on the woman's age: live birth rates per egg retrieval are highest under 35 and fall substantially after 40.

Other options

Donor eggs (very effective for age-related infertility or ovarian insufficiency), donor sperm, gestational surrogacy, sperm retrieval from the testes, and fertility preservation (egg or sperm freezing) before cancer treatment or for planned delay.

Risks of fertility treatment

• multiple pregnancy, which raises risks of preterm birth (minimized by transferring one embryo)
• ovarian hyperstimulation syndrome
• ectopic pregnancy
• emotional and financial strain

Outlook

Many couples with infertility eventually conceive, either without treatment or with it. Outcomes depend most on the woman's age, the cause and how long the couple has been trying. Counseling and support are an important part of care.

Frequently asked questions

What is the most common cause of infertility?

In women, ovulation disorders, especially polycystic ovary syndrome, are the most common treatable cause. Tubal damage, endometriosis and age-related egg decline are also frequent. Male factors contribute to around half of cases, which is why both partners should be tested.

What tests are done for infertility?

Women usually have blood tests to confirm ovulation and check hormones and ovarian reserve, a pelvic ultrasound, and a test of whether the fallopian tubes are open. Men have a semen analysis. Further tests depend on the results.

How successful is IVF?

Success depends mainly on the woman's age and egg quality. Live birth rates per egg retrieval are highest in women under 35 and decline steadily after that, becoming low after about 42 with a woman's own eggs. Using donor eggs gives much higher success rates at older ages.

What is unexplained infertility?

It means standard tests of ovulation, fallopian tubes, the uterus and sperm are all normal, yet pregnancy has not occurred. It affects about a quarter of couples. Options include continued trying, IUI with ovarian stimulation, and IVF, which also gives information about egg and embryo quality.

Can male infertility be treated?

Often, yes. Treatments include stopping testosterone or steroid use, treating hormone problems, repairing a varicocele, clearing blockages, and using IUI or IVF with ICSI. Even men with no sperm in the ejaculate may have sperm retrieved directly from the testes.