Differences between Male and Female Fetuses During pregnancy, one of the most important things is to know whether the fetus in your belly is a boy or a girl to help prepare the baby\’s clothes, toys and other necessities. Three-dimensional color ultrasound has become a method to determine gender, but many people do not know how to identify male and female fetuses. Generally speaking, the differences between male and female fetuses can be determined through the following aspects. Look at the fetal lower body characteristics. When determining the gender of the fetus through three-dimensional color ultrasound photos, it is most important to look at the fetal lower body characteristics.