Differences of Sex Development

At Fertilization

When an egg and sperm meet, the child’s chromosomal makeup is determined. One parent typically gives an X chromosome and the other either an X or Y chromosome. Usually, an XX individual is a female and an XY individual is a male. Sometimes, however, a child gets an extra chromosome from a parent or a chromosome is absent, resulting in XXY, XO or XYY. These differences lead to a DSD.

In Early Fetal Development

When a fetus is just forming during the pregnancy, an organ is present that we call the gonad. It is identical in females and males until midway through the second month of pregnancy. At that time, certain signals inside the fetus direct the gonad to develop into an ovary or a testicle. Any change in these signals can lead to a gonad that doesn’t develop in the typical way. For example, it may contain both ovarian and testicular tissue or may not produce hormones properly.

In Later Fetal Development

Further development leads to a child having organs — typically, a uterus, fallopian tubes, clitoris and labia for females or the seminal vesicles, penis and scrotum for males. At first, every fetus has the potential to develop either set of organs on the inside or outside. After the gonad becomes an ovary or a testicle, it makes hormones that help the body determine which type of structures to develop on the inside and outside. Variations in this development can lead to a range of differences. For example:

• A structure that may look like a small penis or a large clitoris
• A penis with the opening at the base instead of the tip and no testes in the scrotum
• An individual with testicles and male internal structures, but who looks female on the outside

Tests and exams help us know as precisely as possible what caused the difference. Understanding why the DSD occurred helps us to determine the best treatment for the child. Also, we use this information to help the family understand what to expect for their child. The precise cause cannot, however, always be determined.

A DSD brings a complex set of physical, medical and emotional challenges affecting both the child and parents. The approach to care at Lurie Children’s is to address all of these needs in a sensitive manner. Our goal is a happy, healthy child and the best possible future for each individual in our care.