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Non-human mammals [ edit ] The anatomy of the area surrounding an embryo or fetus is different in litter-bearing animals compared to humans: each unborn animal is surrounded by placental tissue and is lodged along one of two long uterine horns rather than in the center of the pear-shaped uterus found in a human female.
In mammals, the term refers chiefly to the early stages of prenatal development, whereas the terms fetus and fetal development describe later stages. [2] [4] The main stages of animal embryonic development are as follows: The zygote undergoes a series of cell divisions (called cleavage) to form a structure called a morula.
A pregnant lioness. 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.
The monotremes branched early from other mammals and do not have the teats seen in most mammals, but they do have mammary glands. The young lick the milk from a mammary patch on the mother's belly. Viviparous mammals are in the subclass Theria; those living today are in the Marsupialia and Placentalia infraclasses.
Bleeding and spotting are common during the luteal phase of the menstrual cycle, and early stages of pregnancy, but are unrelated to implantation. Implantation bleeding occurs between 7 and 14 days after fertilization, [ 56 ] and is a small amount of light vaginal bleeding or spotting that can occur in early pregnancy due to the blastocyst ...
In humans, pregnancy can be defined clinically, biochemically or biologically. Clinically, pregnancy starts from first day of the mother's last period. [4] Biochemically, pregnancy starts when a woman's human chorionic gonadotropin (hCG) levels rise above 25 mIU/mL. [5] Biologically, pregnancy starts at implantation of the fertilized egg.
For months, 30 women breastfed their babies in front of a pregnant orangutan as part of a plan to teach the expecting mother how to care for her newborn at the Dublin Zoo in Ireland.
The obstetrical dilemma is a hypothesis to explain why humans often require assistance from other humans during childbirth to avoid complications, whereas most non-human primates give birth unassisted with relatively little difficulty. This occurs due to the tight fit of the fetal head to the maternal birth canal, which is additionally ...