Ambiguous genitalia

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Ambiguous genitalia is a birth defect where the outer genitals do not have the typical appearance of either a boy or a girl.

See also: Genetics

Genitals - ambiguous

The genetic sex of a child is determined at conception. The mother's egg cell (ovum) contains an X chromosome, while the father's sperm cell contains either an X or a Y chromosome. These X and Y chromosomes determine the child's genetic sex.

Normally, an infant inherits one pair of sex chromosomes -- one X from the mother and one X or one Y from the father. The father "determines" the genetic sex of the child. A baby who inherits the X chromosome from the father is a genetic female (two X chromosomes). A baby who inherits the Y chromosome from the father is a genetic male (one X and one Y chromosome). The male and female reproductive organs and genitals both come from the same tissue in the fetus.

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If the process that causes this fetal tissue to become "male" or "female" is disrupted, ambiguous genitalia can develop. This genitalia makes it difficult to classify the infant as male or female. In very rare instances, the physical appearance may be the opposite of the genetic sex. For example, a genetic male may have the appearance of a normal female.

Usually, ambiguous genitalia in genetic females (babies with two X chromosomes) has the following features:

• An enlarged clitoris that looks like a small penis.
• The urethral opening (where urine comes out) can be along, above, or below the surface of the clitoris.
• The labia may look like a scrotum.
• The infant may be thought to be a male with undescended testicles.
• Sometimes a lump of tissue is felt in the labia, further making it look like a scrotum with testicles.

In a genetic male (one X and one Y chromosome), ambiguous genitalia usually include the following features:

• A small penis (less than 2-3 centimeters or 0.8-1.2 inches) that looks like an enlarged clitoris (the clitoris of a newborn female is normally somewhat enlarged at birth).
• The urethral opening may be along, above, or below the penis; it can be as low as on the peritoneum, further making the infant appear to be female.
• There may be a small scrotum that is separated and looks like labia.
• Undescended testicles commonly occur with ambiguous genitalia.