Pediatric Differences in Sex Development

You have 46 chromosomes in each cell of your body. These are grouped into 23 pairs. The 23rd pair determines your gender. Females have two X chromosomes, and males have one X and one Y chromosome.

The gender of a developing baby is determined at conception, when the embryo has either two XX chromosomes, or an X and a Y chromosome. Around the 6 th week of the unborn baby's development, a gene on the Y chromosome of a developing boy tells the fetal tissue that will form the sex organs to become the testes.

As the testes make testosterone, the penis, scrotum, and urethra form. Then during the 7th to 8th month of the pregnancy, the testes descend into the scrotum.

Without the Y chromosome, the fetal tissue in a female baby that will form the sex organs becomes the ovaries, uterus, and fallopian tubes.

Certain hormones also can affect the development of the sex organs. These hormones are secreted during the early weeks of gestation.

Many genetic and environmental factors can affect the developing baby and lead to atypical genitalia. Ambiguous genitalia may make it harder to determine a baby’s gender. But very few newborns with this condition have genitals that are so ambiguous that the healthcare provider can’t figure out the gender at birth.

These are far more common at birth:

• A girl baby with too much of the male hormones (virilization) who seems to have a small penis
• A boy baby with an abnormally small penis that looks like a female clitoris. This is either because the baby did not respond to male hormones or the baby did not make male hormones.

Atypical genitalia can have a number of different causes. In many cases, healthcare providers don’t know the cause. It seems to occur by chance.

Children who are born with atypical genitalia may fall into one of these groups.

True hermaphroditism

These children have:

• Tissue that is related to both the ovaries and the testes
• Internal sex organs for both genders
• External genitalia that are partly ambiguous
• Chromosomes that are either normal female or male, or a mixture (mosaic)

Gonadal dysgenesis

These children have:

• An undeveloped sex organ
• Internal sex organs that are often female
• External genitals that may vary between normal female and normal male. Most are female.
• Chromosomes that are normal, have only an X chromosome, or are a mixture (mosaic)

Pure gonadal dysgenesis

This affects girls. Those with this condition have male chromosomes, underdeveloped sex organs, internal female reproductive organs, and female external genitalia.

Pseudohermaphroditism in males

Children with this condition have questionable external genitalia. But they have only one gender's internal sex organs. Male pseudohermaphrodite means the child has male internal sex organs. Female pseudohermaphrodite means the child has female internal sex organs.

The two primary causes of male pseudohermaphroditism are androgen insensitivity syndrome and 5-alpha reductase deficiency.

Androgen insensitivity syndrome

These children have:

• Normal male chromosomes
• Normal female external genitalia

This is called androgen insensitivity syndrome because male babies don’t respond to testosterone (androgens). This syndrome is inherited. It's caused by a problem with a gene on the X chromosome. This problem is called X-linked recessive. Mothers who carry the gene have a 1 in 2 chance of having a son with the syndrome. Daughters of mothers who carry the gene have a 1 in 2 chance of being carriers of the gene.

5-alpha-reductase deficiency

Children with this condition have:

• Normal male chromosomes
• Genitals that are ambiguous

Children with this condition lack an enzyme (5-alpha reductase). This enzyme is needed to help the male sex organs complete their development. This condition is inherited. It's caused by an autosomal recessive gene. Autosomal recessive means that each parent carries one copy of the gene and transmits the gene at the same time to the child. Carrier parents have a 1 in 4 chance of having a child with this condition with each pregnancy. It affects only male babies.

Pseudohermaphroditism in females

Female pseudohermaphroditism has a number of causes.

Congenital adrenal hyperplasia (CAH)

Girl babies with this condition have male sex organs. The condition is caused by a lack of a certain enzyme in the adrenal gland. It's the most common cause of atypical genitalia in newborns.

The condition is inherited and passed on by an autosomal recessive gene. Autosomal recessive means that each parent carries one copy of the gene and passes on the gene to the child. Carrier parents have a 1 in 4 chance of having a child with this condition with each pregnancy. Girl babies with the condition have atypical genitalia. Boy babies don't.

In some cases, the mother of a child with this condition can be given medicines during pregnancy to reduce the effects of the enzyme deficiency if the baby is female.

Another type of CAH is called salt-losing. This is very serious and often fatal. It causes an electrolyte collapse in the newborn. Treatment is available if diagnosed early. Boys and girls are equally affected.

Other, rarer enzyme problems can also cause CAH in either boy babies or girl babies.

Overproduction of male hormones before birth

This condition is often caused by a problem with the adrenal glands. High levels of male hormones may also enter the placenta via the mother. This could be when the mother is given progesterone to prevent a miscarriage. Or if she has a hormone-producing tumor.

Sometimes a child with atypical genitalia is at higher risk for tumors in the sex organs. Treatment for atypical genitalia depends on the type of the disorder. But it often includes surgery to remove or create sex organs appropriate for the child's gender. Treatment may also include hormone therapy.

Most important, you and your family should be included early in the decision of assigning the child's sex. Ask your healthcare provider about what is available for long-term psychological support.

When a child's genitalia are ambiguous at birth, your child's healthcare provider will ask about your health history. The health history will include your health during pregnancy and a family history of any neonatal deaths or genital abnormalities. The provider will also do a physical exam of your child's external genitalia.

Your child's provider will look for the underlying cause of the disorder. Your child may need a newborn screening test for CAH, hormone studies and a biopsy of the sex organs.

To figure out the sex, your child's healthcare providers will look at the following:

• A pelvic ultrasound to check for the female sex organs. Or the provider may use direct cystoscopy or vaginoscopy.
• A genitourethrogram to look at the urethra and vagina, if present
• A chromosome study to help figure out the genetic sex of the child
• Evaluation of gene on the Y chromosome that starts development of the male sex organs
• How fertile a child may be who is a female pseudohermaphrodite
• Size and possibility for growth of a penis present in a male pseudohermaphrodite
• Ability of an internal sex organ to make the appropriate sex hormones for the gender assigned to the child
• Risk of future health conditions (such as cancer) that may develop in the original sex organs later in life
• The actions of male or female hormones on the fetal brain
• Your opinion or preference

Making a correct determination of gender is important for treatment. But it's also important for the child's emotional well-being. Some children born with atypical genitalia may have normal internal sex organs that allow them to live normal, fertile lives. But others may have problems with fertility as adults.