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“Test-tube baby” is a term used to refer to a baby produced through artificial insemination or in vitro fertilization, also called IVF. During artificial insemination, a physician injects carefully selected sperm into a women’s uterus to fertilize her eggs. During IVF, a trained professional harvests eggs from a female donor. Those eggs are fertilized with carefully selected sperm in a petri dish.
Rh factor is a protein found on the outside of Rh-positive red blood cells. Rh incompatibility during pregnancy occurs when an Rh-negative mother is pregnant with an Rh-positive fetus. During delivery, the fetus' Rh-positive blood is introduced into the mother’s body. The Rh-negative mother’s body begins to produce antibodies that attack and kill Rh-positive blood cells. Since the crossover of blood normally occurs during delivery, an Rh-negative woman’s first pregnancy is normally not affected.
A germ layer is a group of cells in an embryo that interact with each other as the embryo develops and contribute to the formation of all organs and tissues. All animals, except perhaps sponges, form two or three germ layers. The germ layers develop early in embryonic life, through the process of gastrulation. During gastrulation, a hollow cluster of cells called a blastula reorganizes into two primary germ layers: an inner layer, called endoderm, and an outer layer, called ectoderm.