What is the first stage of human prenatal development?

The first stage of human prenatal development is the germinal period. This stage begins at conception, when the sperm fertilizes the egg, and lasts until the fertilized egg implants itself into the lining of the uterus. During the germinal period, the fertilized egg, now called a zygote, undergoes rapid cell division and begins to develop into a blastocyst. This initial stage is crucial as it sets the foundation for the subsequent stages of development.

In contrast, the embryonic period follows the germinal period and spans from the implantation of the blastocyst until the end of the eighth week of pregnancy. During this time, the major organs and structures of the body begin to form. The fetal period begins after the embryonic period, starting from the ninth week and continuing until birth, characterized by growth and maturation of the previously established structures. The neonatal period refers to the time immediately after birth, which is distinct and comes well after prenatal development.