An egg which had succumbed to the advances of one out of two hundred and fifty million potential suitors implanted by Cadillac.

Of perhaps more interest, they found that the later the egg implanted itself, the greater the chance the pregnancy would fail.

The fertilized egg must then implant in the lining of the uterus.

The thickened endometrium is where a fertilized egg would normally implant and grow.

In-vitro fertilization has also been used and the fertilized egg implanted into a female of either species.

When a fertilized egg has implanted in the uterus, the group of cells that will become a baby is called an embryo.

The fertilised eggs undergo delayed development and do not implant in the female's womb until November.

If the egg does not become fertilized and does not implant menstruation begins.

But not all fertilized eggs successfully implant.

If the egg is not fertilized or does not implant, the woman's body sheds the egg and the endometrium.