At first glance, it looks like the start of a human pregnancy: A ball-shaped embryo presses into the lining of the uterus ...

The 31-year-old pregnant actress, who is expecting her first baby with Justin Theroux, 54, modeled a iridescent, sequined ...

Seals give birth only when conditions are right. After mating, a female seal can delay implantation of the embryo in the uterine wall-pausing pregnancy until she senses that her fat reserves are ...