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.