When a female fetus is developing in its mother's stomach, its own set of eggs (oocytes) are also growing inside its developing ovaries. The eggs start developing at approximately 5-6 weeks of fetal growth.
Between 16-20 weeks of development, the fetus has 6-7 million eggs. Many of these eggs waste away before birth.
By birth, the fetus has 1-2 million eggs. These eggs continue to waste away and die off throughout the years.