Chapter 3 - Prenatal Development, Birth, and the Newborn Flashcards
Define: prenatal development
The changes that transform a fertilized egg into a newborn, takes an average of 38 weeks, divided into three stages.
What are the 3 stages of prenatal development and at what point do each occur?
- The period of the zygote (Weeks 1-2)
- The period of the embryo (Weeks 3-8)
- The period of the fetus (Weeks 9-38)
Describe the main prenatal developments that occur during the period of the zygote.
The zygote grows rapidly through cell division and travels down the fallopian tube toward the uterus. The period ends when the fertilized egg implants itself in the wall of the uterus.
Describe the main prenatal developments that occur during the period of the embryo.
Body structures and internal organs develop.
Define: implantation
The blastocyst burrows into the uterine wall and establishes connections with the mother’s blood vessels. Takes about a week to complete and triggers hormonal changes that prevent menstruation, letting the woman know she has conceived.
Define: placenta
A structure for exchanging nutrients and wastes between the mother and the developing organism.
Define: embryo
The baby from weeks 3-8, after the blastocyst is completely embedded in the uterine wall. Rests in an amniotic sac, which is filled with amniotic fluid that cushions the embryo and maintains a constant temperature.
Define: ectoderm
The outer layer of the embryo, will become hair, the outer layer of skin, and the nervous system.
Define: mesoderm
The middle layer of the embryo, will form muscles, bones, and the circulatory system.
Define: endoderm
The inner layer of the embryo, will form the digestive system and the lungs.
Which two structures link the embryo to the mother?
The umbilical cord and the placenta.
Define: the umbilical cord
Houses blood vessels that join the embryo to the placenta.
At what point in development does the fetus weigh enough for the mother to feel it move?
At about 4 months, roughly 4 to 8 ounces.
Define/explain: the age of viability
By 22 to 28 weeks. Most systems function well enough that a fetus born at this time has a chance to survive.
What is the average increased calorie intake required of a pregnant woman, to meet the needs of prenatal development?
About 10% to 20%.
What are the negative effects to the infant when a pregnant woman does not provide adequate nourishment?
The infant is likely to be born prematurely and to be underweight.
What is one main risk factor when mothers do not consume adequate amounts of folic acid?
Their babies are at risk for spina bifida; a disorder in which the embryo’s neural tube does not close properly during the first month of pregnancy.
What are the different weight gain expectations for normal, underweight, and overweight pregnant women?
A normal woman should expect to gain between 25 and 35 pounds during pregnancy. An underweight woman may gain as much as 40 pounds. An overweight woman should gain at least 15 pounds.
What are the 3 ways chronic stress can harm an infant’s development?
- when a pregnant woman experiences stress, her body secretes hormones that reduce the flow of oxygen to the fetus while increasing its heart rate and activity level
- stress can weaken a pregnant woman’s immune system, making her more susceptible to illness, which can, in turn, damage fetal development
- pregnant women under stress are more likely to smoke or drink alcohol and less likely to rest, exercise, and eat properly
Define: teratogen
An agent that causes abnormal prenatal development.
What are 5 of the most common diseases that are harmful to developing infants?
AIDS, genital herpes, rubella/German measles, syphillis, Cytomegalovirus/herpes.
What are some of the effects of FAS on infants?
-children with FAS usually grow more slowly than normal and have heart problems and misshapen faces, have serious attentional, cognitive, and behavioral problems
How does smoking effect the fetus?
Nicotine in cigarette smoke constricts blood vessels and thus reduces the oxygen and nutrients that can reach the fetus through the placenta.
What are some examples of drug teratogens?
accutane, alcohol, aspirin, caffeine
What are the 5 principles of how teratogens influence prenatal development?
- The impact of a teratogen depends on the genotype of the organism
- a substance may be harmful to one species but not to another, ex. thalidomide safe on pregnant rats/rabbits but not humans - The impact of teratogens changes over the course of prenatal development.
- Each teratogen affects a specific aspect (or aspects) of prenatal development
- The impact of teratogens depends on the dose
- an implication of this principle is that researchers should be able to determine safe levels for a teratogen, this is very difficult because sensitivity to teratogens will not be the same for all people - Damage from teratogens is not always evident at birth, but may appear later in life, ex. cocaine babies had withdrawal right away vs. the drug DES caused cancer later in life
- the impact of teratogens depends on the genotype of the organism as well as the timing and amount of exposure to the teratogen
What are 4 types of prenatal screening/diagnosis?
genetic counselling, ultrasound, cvs, amniocentesis
Define/explain: genetic counseling
a counselor constructs a family tree for each prospective parent to check for heritable disorders, if it turns out that one (or both) carries a disorder, further tests can determine the person’s genotype
How many different genetic disorders can be detected with samples obtained from either amniocentesis or CVS?
about 200
Why is CVS is often preferred over amniocentesis?
Because it can be done about 9 to 12 weeks after conception, nearly 4 to 6 weeks earlier than amniocentesis.
Define: chorionic villus sampling (CVS)
a sample of tissue is obtained from the chorion (a part of the placenta) and analyzed
Define: ultrasound
A standard part of prenatal care in North America. Procedure that uses sound waves to generate a picture of the fetus. Can be used as early as 4 or 5 weeks after conception.
Define: amniocentesis
A needle is inserted through the mother’s abdomen to obtain a sample of the amniotic fluid that surrounds the fetus. Typically performed at approximately 16 weeks after conception.
What are the different things an ultrasound can reveal?
gross physical deformities, twins or other multiple pregnancies, the child’s sex
Define: fetal medicine
A field of medicine concerned with treating prenatal problems before birth, still highly experimental and therefore considered as a last resort.
Define: genetic engineering
Replacing defective genes with synthetic normal genes.
Describe the main features of prepared approaches to childbirth.
Prepared childbirth emphasizes education, relaxation, and the presence of a supportive coach, viewing labour and delivery as life events to be celebrated rather than medical procedures to be endured.
Define: crowning
The point in labour when the top of the baby’s head appears.
Define: breech presentation
Happens in a small percentage of births where the baby comes out feet or bottom first.
Define: hypoxia
The flow of blood through the umbilical cord is disrupted, infants do not receive adequate oxygen.
Define/explain: cesarean section (C-section)
An incision is made in the abdomen to remove the baby from the uterus. Rriskier for mothers than a vaginal delivery because of increased bleeding and greater danger of infection, poses little risk for babies.
Define: premature infants
Born at 35 weeks after conception (or earlier). By age 2 or 3 years, differences in development vanish and most premature infants develop normally thereafter.
Explain the 3 stages of labour and what happens during each stage.
In Stage 1, the muscles of the uterus contract, causing the cervix to enlarge, in Stage 2, the baby moves through the birth canal, in Stage 3, the placenta is delivered.
List and describe the 4 newborn states.
- alert inactivity: the baby is calm, with eyes open and attentive; the baby looks as if he is deliberately inspecting his environment.
- waking activity: the baby’s eyes are open, but they seem unfocused, the baby moves her arms or legs in bursts of uncoordinated motion
- crying: the baby cries vigorously, usually accompanying this with agitated but uncoordinated motion
- sleeping: the baby’s eyes are closed and the baby drift s back and forth from periods of regular breathing and stillness to periods of irregular breathing and gentle arm and leg motion
Define: sudden infant death syndrome (SIDS
A healthy baby dies suddenly, for no apparent reason, more likely when a baby sleeps on its stomach.
Define: co-sleeping
When infants and young children sleep with their parents.
Define: reflexes
Unlearned responses that are triggered by a specific form of stimulation.
