Infertility is when you have trouble getting pregnant or staying pregnant. Fertility problems can happen in women and men, and can have many causes.

Some people have a hard time getting pregnant or staying pregnant. You’re generally diagnosed with infertility if you don’t get pregnant after 1 year or more of trying, or if you have multiple miscarriages. There are treatments for many kinds of infertility, and many people go on to have a healthy pregnancy and a child.

Millions of people — more than 1 out of 10 couples — experience fertility problems. And it’s not just a “woman’s problem” or an issue with age. Lots of things can lead to infertility, and it can affect people of any sex and all ages.

There are lots of possible causes of infertility. Consulting a doctor that is specialized in infertility can help you figure out what’s causing your fertility problems and find the best treatments for you. Sometimes there’s no known reason for infertility — this is called unexplained infertility. Unexplained infertility can be really frustrating, but there are still usually treatment options that you can try.

Some common reasons for infertility in women include:

• untreated chlamydia or gonorrhea
• not ovulating (not releasing eggs from your ovaries)
• your fallopian tubes are blocked so sperm can’t get to your egg
• poor egg quality
• the shape of your uterus makes it hard for a fertilized egg to implant
• endometriosis
• uterine fibroids

The most common causes of infertility in men include:

• untreated chlamydia or gonorrhea
• low sperm count (not having enough sperm in your semen)
• poor sperm motility (when sperm doesn’t swim well enough to reach an egg)
• sperm that aren’t formed correctly
• semen that’s too thick for sperm to easily move around in it
• no sperm in your semen

Having too much or too little of some of the hormones that help your body make sperm can also lead to sperm-related problems that cause infertility.

Infertility can also be caused by a problem with ejaculation. If the tubes inside your penis or testicles are blocked, you may have a hard time ejaculating, or nothing comes out when you have an orgasm. Sometimes, ejaculation can send semen backward from your prostate into your bladder, instead of out of your penis.

What might increase risk of infertility?

There are certain health and lifestyle factors that can increase your chances of having fertility problems. They include:

• being older than 35 (for women)
• being very overweight or underweight
• chemotherapy or radiation
• lots of exposure to environmental toxins, like lead or pesticides
• excessive drug or alcohol use
• smoking cigarettes
• not getting recommended testing for chlamydia/gonorrhea
• a history of pelvic inflammatory disease (PID)
• injury to the scrotum and testes
• overheated testicles (from wearing clothing that’s too tight, or swimming or bathing in hot water often and recently)
• having an undescended testicle