Being rather skeptical, I consulted my dictionary.
Conception occurs when sperm fertilizes an ovum, forming a zygote.
The blastula stage of the embryo that implants in the wall of the uterus takes about 72 hours following conception to develop from a zygote. Human embryology teaches that each human life begins at conception. It also defines, describes and labels the stages of development from zygote to birth. Specifically, for about the first three months of pregnancy, from the zygote to the fetus, the developing human is called an embryo. And that is undoubtedly the determination that Wal-Mart has made.