Question

The time during which a viviparous animal carries an embryo or fetus inside its womb is known as ………………….

Answer 1

This period is a developmental period during which a viviparous animal carries an embryo or fetus inside its womb. It is most typical for mammals but also occurs in some non-mammals.

Complete answer:
The period of development during which a viviparous animal carries an embryo or fetus inside its womb is known as gestation period.
The time interval of gestation is called the gestation period which is the process or period of developing inside the womb between conception and birth. In human obstetrics, gestational age mainly refers to the fertilization age plus two weeks.
Gestation in mammals is basically defined as the duration between conception and birth of a young one, during which the embryo or fetus is developing in the uterus. But this statement raises some difficulties because in some species for example monkeys and man, the exact time of conception may not be known. In such a case the beginning of gestation is usually dated from some well-defined point in the reproductive cycle like the beginning of the previous menstrual period.
Additionally, the length of gestation also varies from species to species. The shortest known gestation is that of the Virginia opossum that is about 12 days, and the longest that of the Indian elephant, about 22 months. The duration of gestation has become adapted to the needs of the species, during the course of evolution.

So the correct answer to this question is ‘Gestation period’.

Additional information:
Several hormones play major roles during pregnancy mainly:
-Human chorionic gonadotropin hormone (hCG): It is produced exclusively from the placenta. hCG hormone levels rise in the mother's blood during the first trimester. It also causes nausea and vomiting.
-Human placental lactogen (hPL). Also known as human chorionic somatomammotropin. Its main function is to give nutrition to the fetus. It also stimulates mammary glands in the breasts for breastfeeding.
-Estrogen. This group of hormones develop female sexual characters and is formed in the ovaries. It also aids in maintaining a healthy pregnancy.
-Progesterone. This hormone is produced in the ovaries and placenta during pregnancy. Its main function is to stimulate the thickening of the uterine lining for implantation of a fertilized egg

Notes:
Ovoviviparous embryos are nourished by the egg yolk rather than by the mother's body as in the case of viviparous embryos. However, the mother's body provides gaseous exchange. Additionally, the young ones of ovoviviparous amphibians are sometimes born as larvae and undergo a process known as metamorphosis outside the body of the mother.