When Does Gender Development Occur In Babies

Soon to be parents are understandably curious about whether they’re going to have a boy or a girl. In countries or jurisdictions where gender determination is legal, some couples would like to know the sex of their unborn baby, while others could keep it a surprise. While you may not be able to see the sex organs of a baby on the sonogram or the ultrasound for weeks, the baby’s sex is determined much before the baby arrives into the world. Here, we look at when does a baby develop gender.


Gender Determination:

Your baby’s gender is determined soon after fertilization. In fact, the gender is determined even before your baby matures into a fetus. It is the 23rd pair of chromosomes that assigns the gender. We know that a mother’s egg contains an X chromosome while the father’s sperm carries an X or Y chromosome. A combination of XX would result in a female child whereas a combination of XY

results in a male child. It pretty much explains that baby’s gender is determined during fertilization.


A baby’s external and internal genital structures are the same during the first few weeks of fetal development, but they change eventually; the gonads become either testicles or ovaries, the phallus becomes either penis or clitoris, and the genital fold becomes either a scrotum or a labia. The development of male genital structure depends on the presence of testosterone in embryos with a Y chromosome. If testosterone is absent female organs develop. Apart from testosterone an anti-Mullerian hormone or AMH also determines the development of sex organs.

As the embryo develops, it develops both in Mullerian ducts and Wolffian ducts, which develop into female and male sex organs. The genitalia begins to form at the eighth week. The testosterone will stimulate the Wolffian duct to develop male sex organs if the embryo has both an X and a Y chromosome and produces the two hormones. If there are two X chromosomes instead of a Y chromosome, then the Wolffian duct degenerates and the Mullerian

duct develops to make the female sex organs. It is a rare case where the embryo has an X and a Y chromosome but does not produce testosterone or AMH. But, when this happens, it is called intersex because of the presence of both male and female sex organs. It is only after the internal sex organs develop that the external genitals continue to develop.

Here’s When Sex Organs Become Visible:

It is not until the sixteenth or the eighteenth week of pregnancy that you will be able to determine your baby’s sex. Your baby would develop a small bud called the genital tuber at the site of the genitals around the sixth week. It would seem alike for boys and girls until around the ninth week when the sex organs begin to form. At the end of the twentieth week, the external sex organs are fully formed in both the male and female babies.

It is around the 20th week when an ultrasound can reveal the sex of your baby. While your baby’s gender is determined at the exact moment

when fertilization takes place, it takes time for the external organs to match the internal chromosomes.

Intersex Babies:

The term ‘intersex’ is used to describe some conditions for people born with a sexual anatomy that doesn’t fit into the definitions of male or female. If a person is born with both XX and XY chromosomes, such people would have genitals between male and female parts; however the condition is very rare.

Controversy About ‘Gender’:

The use of the term ‘gender’ has become quite controversial as gender is what some believe purely depends on a child’s development. If a child is exposed to a pink room and taught to play with dolls, then the child with identifying as a girl. If exposed to a blue room and taught to play with trucks, a child will identify a boy. However, studies suggest that by the age of two or three, your child would have developed the awareness of being a male or a female and behave accordingly.