1.   If fertilization does take place, the embryo can implant in a blocked Fallopian tube rather than uterus and result in an ectopic pregnancy.

2.   One is the stage when embryos would normally implant in a uterus.

3.   Rarely did all embryos implant and grow into fetuses because the laboratory and surgical techniques were still in their infancy.

4.   Pregnancy occurs when the embryo implants in the uterine wall.

5.   The embryo had implanted itself, not in the uterus but in the Fallopian tube, where it could never develop.

6.   Their work shows that genetically identical mouse embryos implanted in different wombs end up performing differently at mental tasks.

7.   Through improved techniques, the single embryo will implant itself in the womb, split on occasion into twins, but otherwise grow into one healthy baby.