What is the prenatal period?
The prenatal period extends from conception to birth, usually encompassing nine months of pregnancy.
How does the rate of development during prenatal period compare to postnatal growth?
Development during the prenatal period is remarkably rapid.
What are the three phases of prenatal development?
- Germinal stage (first two weeks)
- Embryonic stage (two weeks to two months)
- Fetal stage (two months to birth)
What begins the germinal stage of prenatal development?
A zygote is created through fertilization.
What occurs within 36 hours after fertilization during the germinal stage?
Rapid cell division begins and the zygote becomes a microscopic mass of multiplying cells.
What happens on about the seventh day of the germinal stage?
The cell mass begins to implant itself in the uterine wall.
What is the role of the placenta during the germinal stage?
The placenta allows oxygen and nutrients to pass into the fetus from the mother’s bloodstream.
What is the duration of the embryonic stage?
The embryonic stage lasts from two weeks until the end of the second month.
What major developments occur during the embryonic stage?
Most vital organs and bodily systems begin to form.
What is the size of the embryo at the end of the embryonic stage?
About 2.5 cm long.
What is the significance of the embryonic stage regarding vulnerability?
It is a period of great vulnerability as all basic physiological structures are being formed.
What major issues can arise from interference during the embryonic stage?
- Most miscarriages
- Most major structural birth defects
What is the duration of the fetal stage?
The fetal stage lasts from two months through birth.
What significant changes happen during the first two months of the fetal stage?
Rapid bodily growth, as muscles and bones begin to form.
What begins to develop during the third month of the fetal stage?
Sex organs start to develop.
What occurs during the final three months of prenatal development?
- Brain cells multiply
- A layer of fat is deposited under the skin
- Respiratory and digestive systems mature
What is the threshold of viability for a fetus?
The age at which a baby can survive in the event of a premature birth, typically between 23 to 25 weeks.
What is the survival probability at 23 weeks and at 25 weeks of gestation?
23 weeks: about 20 percent survival rate; 25 weeks: around 67 percent survival rate.
True or False: Most miscarriages occur during the fetal stage.
False
Fill in the blank: The developing organism is called a _______ during the fetal stage.
fetus
