Delayed Implantation is a reproductive strategy used by almost 100 different mammals in seven different orders.

In delayed implantation the embryo does not immediately implant in the uterus, but it is maintained in a state or dormancy. No development takes place during this period and as a result the normal gestation period is extended, sometimes by as much a one year.

Two types of Delayed Implantation have been identified:

Facultative Diapause - this is a mechanism that is associated with metabolic stress, usually lactation. If a female becomes pregnant while still lactating for her original youngster, the sucking stimulus will cause the embryos to enter into diapause.

Obligate Diapause - this is a mechanism to allow mammals to time the birth of their youngsters with favorable environmental conditions.

Associated terms: Embryonic Diapause, Facultative Arrest, Obligate Arrest

Also see:
Zygote
Embryo
Foetus
Placenta
Uterus
Gestation Period
Fertilization
Sexual Reproduction