Infertility: what it means, common causes and risk factors

Many couples wonder why pregnancy is taking longer than expected. This article explains what infertility means, what can cause it and which risk factors matter, using information from the NHS, MedlinePlus and the US National Institute of Child Health and Human Development (NICHD).

1. Introduction

Infertility means a couple cannot get pregnant (conceive) despite having regular unprotected sex. The NHS describes regular sex as every 2 or 3 days ^[1]. It is common. The NHS says about 1 in 7 couples may have difficulty conceiving, yet when the woman is under 40, more than 8 in 10 couples conceive naturally within a year ^[1].

There are two types. Primary infertility means someone who has never conceived a child is having difficulty conceiving. Secondary infertility means someone who has had one or more pregnancies is having difficulty conceiving again ^[1]. The NHS adds that infertility is usually only diagnosed and treated after 2 years of trying through regular unprotected sex, and that for couples who have tried for more than 3 years without success, the chance of pregnancy in the next year is 1 in 4 or less ^[1].

2. How infertility is defined

The NICHD and MedlinePlus both define infertility as not becoming pregnant after 1 year of regular, unprotected sex. MedlinePlus says this shortens to 6 months for women aged 35 or older, and the NICHD says 6 months if the woman is older than 35 ^{[3, 4]}. MedlinePlus adds that the word can also cover repeated miscarriage or stillbirth ^[3]. The NICHD uses the word subfertility for couples who are likely to conceive without medical help but take longer than usual ^[4].

MedlinePlus notes that infertility affects both men and women, and both partners can contribute ^[3]. The NICHD likewise says male and female factors are about equally likely, and a mix of both is also common ^[5].

3. Common causes in women

The NHS lists several causes ^[2]:

• Ovulation problems. Ovulation is the monthly release of an egg. Some conditions stop it or make it irregular, including polycystic ovary syndrome (PCOS), an overactive or underactive thyroid, and premature ovarian failure, where the ovaries stop working before age 40.
• Scarring. Pelvic surgery can scar the fallopian tubes, which carry the egg to the womb. Surgery on the cervix, the neck of the womb, can scar or shorten it.
• Cervical mucus. If the mucus is not thin enough around ovulation, sperm may find it harder to pass.
• Fibroids. These are non-cancerous growths in the womb. They can block a tube or stop a fertilised egg from attaching.
• Endometriosis. Tissue similar to the womb lining grows elsewhere and can damage the ovaries or tubes.
• Pelvic inflammatory disease. This is an infection of the upper genital tract, often from a sexually transmitted infection, and it can scar the tubes.

MedlinePlus also names age-related egg problems and hormone imbalances ^[3]. Some medicines can affect fertility too. The NHS mentions long-term or high-dose anti-inflammatory painkillers, chemotherapy and some other prescribed medicines, and cannabis and cocaine ^[2]. Never stop a prescribed medicine without asking your doctor first.

4. Common causes in men

The NHS says semen and sperm problems are a common cause. These include a low sperm count or no sperm, sperm that do not move properly and sperm with abnormal shapes ^[2]. Other causes include:

• Damage to the testicles from infection, testicular cancer, surgery, injury or being born with undescended testicles ^[2].
• Ejaculation problems, which make it hard to release semen during sex ^[2].
• Low testosterone, a condition called hypogonadism ^[2].
• Blocked ducts that carry sperm, past high fevers or mumps, and genetic disorders ^{[3, 6]}.

5. When no cause is found

The NHS says that in about a quarter of cases no cause can be found ^{[1, 2]}. This is called unexplained infertility. It can be hard emotionally. MedlinePlus says many couples who receive treatment go on to have children ^[3].

6. Risk factors

The NHS and MedlinePlus list these risk factors ^{[1, 3]}:

• Age. Fertility declines as people get older.
• Weight. A body mass index of 30 or more reduces fertility, and being very overweight or very underweight can affect ovulation in women.
• Sexually transmitted infections, such as chlamydia.
• Smoking, including passive smoking, which lowers the chance of conceiving and can reduce semen quality.
• Alcohol. The NHS says the safest approach while trying to conceive is to avoid alcohol, and heavy drinking can affect sperm quality.
• Environmental exposure to certain pesticides, solvents and metals, particularly in men.
• Stress, which can strain relationships and reduce desire for sex. In severe cases it may affect ovulation and sperm production.

Not all infertility can be prevented. MedlinePlus suggests that quitting smoking, limiting alcohol, keeping a healthy weight and practising safe sex to avoid infections may lower the risk ^[3].

7. When to see a doctor

The NHS advises seeing a GP after a year of trying without success. Go sooner if the woman is 36 or over, or if you already know you may have a fertility problem ^[1]. MedlinePlus advises seeking care if you are over 40, have irregular periods, have had pelvic inflammatory disease or have had fertility concerns before ^[3]. Fertility problems can affect either partner or both ^[1].

In an emergency, call your local emergency number (112 in India, 911 in the United States).

8. Conclusion

Infertility is common and has many possible causes in women, in men or in both. For about 1 in 4 couples no cause is found. Age, weight, smoking, alcohol and infections all play a part, and some of these can be changed. A doctor can check for the common causes and explain the options, and the doctor decides which tests and treatments are right for you.