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Prenatal development (from Latin natalis 'relating to birth') involves the development of the embryo and of the fetus during a viviparous animal's gestation.Prenatal development starts with fertilization, in the germinal stage of embryonic development, and continues in fetal development until birth.
The cochleae are now developed, though the myelin sheaths in neural portion of the auditory system will continue to develop until 18 months after birth. The respiratory system, while immature, has developed to the point where gas exchange is possible.
Development before birth, or prenatal development (from Latin natalis 'relating to birth') is the process in which a zygote, and later an embryo, and then a fetus develops during gestation. Prenatal development starts with fertilization and the formation of the zygote , the first stage in embryonic development which continues in fetal ...
Organogenesis is the development of the organs that begins during the third to eighth week, and continues until birth. Sometimes full development, as in the lungs, continues after birth. Different organs take part in the development of the many organ systems of the body.
Once the fetus is sufficiently developed, chemical signals begin the process of birth, which begins with the fetus being pushed out of the birthing canal. The newborn, which is called an infant in humans, should typically begin respiration on its own shortly after birth. Not long after, the placenta eventually falls off on its own.
The average time to birth has been estimated to be 268 days (38 weeks and two days) from ovulation, with a standard deviation of 10 days or coefficient of variation of 3.7%. [33] Fertilization age is sometimes used postnatally (after birth) as well to estimate various risk factors.
It is also suggested that a birth plan be written at this time. A birth plan is a written statement that outlines the desires of the mother during labor and delivery of the baby. Discussing the birth plan with the midwife or other care provider gives parents a chance to ask questions and learn more about the process of labour. [150]
Mammals during pregnancy can have one or more gestations at the same time, for example in a multiple birth. [2] The time interval of a gestation is called the gestation period. In obstetrics, gestational age refers to the time since the onset of the last menses, which on average is fertilization age plus two weeks. [3]