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The mammals included are only viviparous (marsupials and placentals) as some mammals, which are monotremes (including platypuses and echidnas) lay their eggs. A marsupial has a short gestation period, typically shorter than placental. For more information on how these estimates were ascertained, see Wikipedia's articles on gestational age.
The cleavage stages of marsupial development are very variable between groups and aspects of marsupial early development are not yet fully understood. An infant marsupial is known as a joey . Marsupials have a very short gestation period—usually between 12.5 and 33 days, [ 41 ] but as low as 10.7 days in the case of the stripe-faced dunnart ...
Gestation, called pregnancy in humans, is the period of time during which the fetus develops, dividing via mitosis inside the female. During this time, the fetus receives all of its nutrition and oxygenated blood from the female, filtered through the placenta , which is attached to the fetus' abdomen via an umbilical cord .
The latter subclass is divided into two infraclasses: pouched mammals (metatherians or marsupials), and placental mammals (eutherians, for which see List of placental mammals). Classification updated from Wilson and Reeder's "Mammal Species of the World: A Taxonomic and Geographic Reference" using the "Planet Mammifères" website. [1]
In mammals, pregnancy is the period of reproduction during which a female carries one or more live offspring from implantation in the uterus through gestation. It begins when a fertilized zygote implants in the female's uterus , and ends once it leaves the uterus.
[5] [14] Amongst marsupials, the golden bandicoot is known to have one of the highest reproductive rates, and it has one of the shortest gestation periods for mammals, only about 12 days. [ 9 ] [ 14 ] There are about 2–3 young per litter, and they remain in the pouch of the mother for up to 8 weeks.
While you don’t need to track hCG throughout you nine-month gestation, an hCG levels chart can inform doctors about the health of your pregnancy.
The class Mammalia is divided into two subclasses based on reproductive techniques: monotremes, which lay eggs, and therians, mammals which give live birth, which has two infraclasses: marsupials/metatherians and placentals/eutherians. See List of monotremes and marsupials, and for the clades and families, see Mammal classification ...