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Ambiguous genitalia

  • Definition

    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

    Alternative Names

    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.

    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.

    Ambiguous genitalia is usually not life threatening, but it can create social problems for the child and family. For this reason, a team of experienced specialists, including neonatologists, geneticists, endocrinologists, and psychiatrists or social workers will be involved in the child's care.

    Common Causes
    • Pseudohermaphroditism. The genitalia are of one sex, but some physical characteristics of the other sex are present.
    • True hermaphrodism. A very rare condition in which tissue from both the ovaries and testicles is present. The child may have parts of both male and female genitals.
    • Mixed gonadal dysgenesis (MGD). An intersex condition in which there are some male structures (gonad, testis), as well as a uterus, vagina, and fallopian tubes.
    • Congenital adrenal hyperplasia. This condition has several forms, but the most common form causes the genetic female to appear male. Many states test for this potentially life-threatening condition during newborn screening exams.
    • Chromosomal abnormalities, including Klinefelter's syndrome (XXY) and Turner's syndrome (XO).
    • If the mother takes certain medications (such as androgenic steroids), they may make a genetic female look more male
    • Lack of production of certain hormones can cause the embryo to develop with a female body type, regardless of genetic sex
    • Lack of testosterone cellular receptors. Even if the body makes the hormones needed to develop into a physical male, the body cannot respond to those hormones. This produces a female body-type, even if the genetic sex is male.