identical and fraternal twins
Identical (one-egg) twins and fraternal (two-egg) twins both receive nourishment that passes from the mother's blood through the placenta and into the fetal blood vessels in the umbilical cord. In about 70 percent of one-egg twins there is only one chorion and one placenta. Each of the two-egg twins has a chorion and, usually, a separate placenta; in some cases they share a placenta.
multiple birth
mammalogy
Also known as: supertwins
- Related Topics:
- twin
- nonuplet
- quintuplet
- octuplet
- quadruplet
multiple birth, the delivery of more than one offspring in a single birth event. In most mammals the litter size is fairly constant and is roughly correlated with, among other features, body size, gestation period, life span, type of uterus, and number of teats. For example, a large mammal with a normal pregnancy of more than 150 days, a life span of more than 20 years, a simple (or unicornuate) uterus, and two breasts rarely bears more than one young (a singleton) at a birth. The great majority of primates, humans included, fit into this category; multiple births among them ...(100 of 1104 words)