Natural Birth and Baby Care.com

When Does the Fetus Complete Gender?

by Preeti Singh
(India)

I would like to know when the fetus completes gender development. What week is the fetus completely male or female?

Answer:

The sex of a baby is determined at conception. An egg is either fertilized by XX sperm (female) or XY sperm (male). This doesn't change. It's there at the beginning of development. It's true that maternal hormones may have some effect on the baby's system, but the baby's sex is determined by what sperm fertilizes the egg.

The development of the sex organs is not complete right away, of course. The baby develops those organs along with all the others. Until around 7 weeks or so male and female babies all have the same structures. After that point the babies organs will either develop into a female's labia, clitoris, and other female organs - or testicles, penis, and other male organs.

You may want to get the book A Child Is Born, which has excellent pictures of the development of babies. It shows weekly growth and development and pictures how the baby at first has very neutral organs which then develop into either female or male genitalia.