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. The genitalia makes it difficult to easily identify the infant as male or female. The extent of the ambiguity varies. In very rare instances, the physical appearance may be fully developed as the opposite of the genetic sex. For example, a genetic male may have developed the appearance of a normal female.
Typically, 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 anywhere along, above, or below the surface of the clitoris.
The infant may be thought to be a male with undescended testicles.
Sometimes a lump of tissue is felt within the fused 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 3/4 to 1 1/4 inches) that looks like an enlarged clitoris (the clitoris of a newborn female is normally somewhat enlarged at birth).
The urethral opening may be anywhere along, above, or below the penis. It can be located as low as on the perineum, 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 (see Causes section for exceptions), 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.
Pseudohermaphroditism. The genitalia are of one sex, but some physical characteristics of the other sex are present.
True hermaphroditism. This is 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). This is 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.
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.
Because of the potential social and psychological effects of this condition, parents should make a decision about whether to raise the child as a male or female early after diagnosis, preferably within the first few days of life. This is an important decision, so parents should not rush it.
When to Contact a Medical Professional
You are concerned about the appearance of your child's external genitalia, or your baby:
Takes more than 2 weeks to regain his or her birth weight
Looks dehydrated (dry inside of mouth, no tears when crying, less than 4 wet diapers per 24 hours, eyes look sunken in)
Have any family members had infants who died in the first few weeks of life or who had ambiguous genitalia?
Is there any family history of any of the disorders that cause ambiguous genitalia?
What medications did the mother take before or during pregnancy (especially steroids)?
What other symptoms are present?
Genetic testing can determine if the child is a genetic male or female. Often a small sample of cells can be scraped from inside the child's cheeks (this is called a buccal smear). Examining these cells is often enough to determine the genetic sex of the infant. Chromosomal analysis is a more extensive cell study that may be needed in more questionable cases.
Endoscopy, abdominal x-ray, abdominal or pelvic ultrasound, and similar tests may be needed to determine the presence or absence of the internal genitals (such as undescended testes).
Laboratory tests may help determine how well the reproductive organs are functioning. This can include tests for adrenal and gonadal steroids.
Depending on the cause, surgery, hormone replacement, or other treatments are used to treat conditions that can cause ambiguous genitalia.
Sometimes, the parents must choose whether to raise the child as male or female (regardless of the child's chromosomes). This choice can have a big social and psychological impact on the child, so counseling is usually recommended.
Note: It is often technically easier to treat (and therefore raise) the child as female (it is easier for a surgeon to make female genitalia than it is to make male genitalia), so in some cases this is recommended even if the child is genetically male. However, this is a difficult decision. You should discuss it with your family, your child's doctor, the surgeon, your child's endocrinologist, and other health care team members.
Diamond AD, Yu RN. Sexual differentiation: Normal and abnormal. In: Wein AJ, ed. Campbell-Walsh Urology. 10th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 133.
Neil K. Kaneshiro, MD, MHA, Clinical Assistant Professor of Pediatrics, University of Washington School of Medicine. Also reviewed by A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, Bethanne Black, Stephanie Slon, and Nissi Wang.