Triple X, also called trisomy X and 47,XXX, is a genetic condition that occurs when a girl receives three X chromosomes from her parents. Typically, girls only receive two X chromosomes. The extra X chromosome can have no effect on a girl’s health, or it can cause physical and mental abnormalities that may range from very mild to more pronounced.

Triple X affects 1 in 1,000 females. According to the National Institutes of Health, 5 to 10 girls are born with the disorder in the United States every day.

Some girls and women with triple X syndrome show no symptoms at all, causing the disorder to go undiagnosed. In fact, it’s estimated that only 10 percent of females affected are ever diagnosed.

If symptoms do occur, they commonly include physical abnormalities like:

  • a smaller-than-average head
  • being taller than average (with especially long legs)
  • poor muscle tone

Without strong and developed muscles, babies with triple X may be slow to walk. As they grow older, they may be clumsier than girls without the syndrome. Although it’s rare, some females with triple X may have kidney problems, seizures, and heart problems.

Read more: Should you be worried if your 14-month-old isn’t walking? »

Speech and language delays are other symptoms of triple X. Many with triple X have learning disabilities, involving reading and difficulty with speech and language. A review of studies found some evidence that girls with triple X may have an IQ about 20 points lower than girls without the disorder.

Chromosomes are molecules found in cells that give us our genetic makeup, like skin, eye, and hair color, and gender. We get these chromosomes from our parents. People are usually born with 46 chromosomes, including a pair of sex chromosomes: XY (male) or XX (female).

Due to a random malfunction in the way cells split at or right after conception, a girl may receive three X chromosomes, resulting in triple X. Some females have a third X chromosome in only some of their cells, resulting in no or very mild symptoms of the disorder.

If your child is born with triple X, it’s important to remember that there was nothing you could have done to prevent this.

Having an extra X chromosome may affect areas of the brain that control what experts call executive functioning. People who don’t have strong executive functioning may find it hard to focus, manage time, and get along with others.

Research suggests that girls with triple X have more anxiety, less-developed social skills, and higher rates of autism. In a study published in the Journal of Developmental and Behavioral Pediatrics, 52 percent of girls who had been diagnosed with triple X met the criteria for attention deficit hyperactivity disorder (ADHD). Because of all these factors, girls with the condition can experience low self-esteem and low self-confidence, and have problems with interpersonal relationships.

Read more: Why do girls show signs of autism later than boys? »

Menopause occurs when a woman no longer produces enough hormones to release an egg each month, making her unable to become pregnant. For most women, menopause occurs around age 50.

Some research indicates that women with triple X can stop producing eggs at a younger than average age. If that happens, they may go through menopause early, and then be unable to get pregnant.

In fact, triple X is often first diagnosed when a woman sees her doctor about fertility concerns. Because the condition so often goes undiagnosed, there isn’t a lot of research on the subject.

Learn more: What causes early menopause? »

In general, experts note that most women with triple X have normal sexual development and are able to become pregnant and deliver healthy babies just like women without the disorder.

Most women and girls with triple X syndrome don’t exhibit any outward signs. They live healthy lives, which is why so many cases go undetected. A diagnosis can be made through genetic testing. This testing can be performed after birth by taking a blood sample. It can also be done before birth by more sophisticated tests like amniocentesis and chorionic villus sampling, which analyze the tissues and cells of a fetus.

There is no cure for triple X syndrome. A girl born with the disorder will always have a third X chromosome. Treatment involves providing support for girls and women to manage their symptoms.

  • Developmental delays respond well to speech and physical therapy.
  • Learning disabilities can be addressed with education plans.
  • Behavioral issues can be managed with counseling, and psychological and family support. There are also support groups for those with triple X.

Experts agree that girls who receive early intervention can perform just as well as girls without the condition. Those diagnosed with triple X syndrome should also be monitored by their healthcare provider. Some females with the disorder can have heart and kidney problems.

Triple X isn’t uncommon, but its symptoms can be so mild and subtle that it’s often undiagnosed. When a girl isn’t meeting developmental milestones, triple X syndrome should be investigated. A team of specialists is best equipped to handle the condition, and may include:

  • neurologists
  • developmental pediatricians
  • speech and occupational therapists
  • mental health experts

Starting treatments like speech and physical therapy and counseling early can head off problems later. Most girls with triple X can lead normal, healthy lives, especially when they’re diagnosed and treated early.