Female, Male & Intersex at a Glance
- Biological sex is our anatomy as female, male, or intersex.
- It includes our internal and external sex organs, chromosomes, and hormones.
- Some people are intersex rather than female or male.
Our biological sex is how we are defined as female, male, or intersex. It describes our internal and external bodies — including our sexual and reproductive anatomy, our genetic makeup, and our hormones.
It’s normal to have questions about biological sex. Here are some of the most common questions we hear about what it means to be female, male, or intersex. We hope they help.
Find a health center & book an appointment
What Is Biological Sex?
Biological sex identifies a person as either female, male, or intersex. It is determined by a person’s sexual anatomy, chromosomes, and hormones. Biological sex is often simply referred to as “sex.”
Our biological sex is established when an egg is fertilized. Most often, men ejaculate two types of sperm. One type has X chromosomes and the other type has Y chromosomes. Most often
- When sperm fertilizes an egg, its X or Y chromosome combines with the X chromosome of the egg.
- A person with XX chromosomes and female sex and reproductive organs is biologically female. Upon reaching puberty, that person will produce hormones that will cause breasts and other female characteristics to develop and menstruation to begin.
- A person with XY chromosomes and male sex and reproductive organs is biologically male. Upon reaching puberty, that person will produce hormones that will cause sperm production and other male characteristics to develop.
Sometimes, a child is born with sex chromosomes that are different from the usual XX of the female or the XY of the male. The child may develop sex and/or reproductive organs that are ambiguous — not completely female and not completely male. Ambiguous sex organs can develop for other reasons, as well. These are called intersex conditions.
Most people agree that babies with intersex conditions should be assigned a gender at birth. Some people believe that assigning a gender means performing surgery on the baby's genitals, while others believe that a baby can be raised as a girl or boy without surgery. Some people believe surgery should be postponed until intersex people are old enough to decide for themselves.
If you have a child who is intersex, open conversation about gender is important throughout your child's life — whether or not your child has sex-assignment surgery. It can help your child develop a healthy gender identity and body image.
What’s the Difference Between Sex and Gender?
It’s common for people to confuse biological sex and gender. Our sex only refers to our sexual anatomy and chromosomes. Our gender is our biological, social, and legal status as girls and boys, women and men. Each culture has standards about the way that people should behave based on their gender. For example, many cultures expect and encourage men to be more aggressive than women.
Our gender identity is our innermost feelings about our sex and gender. Some people have a gender identity that strongly conflicts with their biological sex — they are called transgender.
How Common Are Intersex Conditions?
It is common to believe that all people fall into one of two categories — female or male. But that is not true. Some people are born with external sex organs that are not easily identifiable as female or male. Other people have sex chromosomes that are different from the usual XX (female) or XY (male). People whose biological sex is not clear in these ways have intersex conditions. About 1 in 2,000 people born in the U.S. is intersex. There are many different ways that intersex conditions appear.
Genitals that are not easily identifiable as female or male are sometimes apparent at birth. But sometimes it is not obvious until puberty. People with intersex conditions may be considered sexually ambiguous in different ways:
- They may have sex organs that appear to be somewhat female or male or both. They do not, however, have complete female genitals and complete male genitals.
- They may have a large clitoris — more than two-fifths of an inch long.
- They may have a small penis — less than an inch long.
Some babies are born with both ovarian and testicular tissue.
Some people have chromosomes that are different. Two common chromosomal intersex conditions are:
- Turner Syndrome = XO
- Klienfelter’s Syndrome = XXY
There are other differences a person could have that cannot be found without testing chromosomes and hormones, or examining internal sex organs. Sometimes the difference is never noticed, so some people have intersex conditions for their whole lives and never know.
Some intersex people are transgender, but intersex does not necessarily mean transgender, and transgender does not necessarily mean intersex.
How Do Doctors Treat Intersex Babies?
Sometimes a female or male sex is assigned to a baby through surgery. Up to five of these surgeries occur every day in the U.S.
Many people think that babies with intersex conditions should be assigned a gender at birth. Some people believe that assigning a gender means performing surgery on the baby’s genitals, while others believe that a baby can be raised as a girl or boy without surgery. Some people think surgery should be postponed until intersex people are old enough to decide for themselves.
If you have a child who is intersex, open conversation about gender is important throughout your child’s life — whether or not your child has gender-assignment surgery. It can help your child develop a healthy gender identity and body image.