1.   But in these cases the implanted embryos were not the result of cloning.

2.   He pointed out that laws generally define abortion as removal of an implanted embryo.

3.   Without progesterone, the uterine lining -- with the implanted embryo -- begins to detach from the uterus.

4.   Scientists had previously shown it is possible for one species to give birth to implanted embryos taken from a similar species.