CD Chapter 4 Prenatal Development
I.
The Developing Baby
A.) Family Planning
1.) Most methods of contraception do not prevent sexually transmitted infections (STI’s).
2.) Methods of Family Planning-The only method that is 100% effective is abstinence.
B.) Conception
1.) The process of the sperm fertilizing the ovum is called conception.
2.) About once every 28 days, an ovum is released by one of the woman’s two ovaries. An
ovum is an egg cell. This release is part of a woman’s menstrual cycle and is called
ovulation. When the ovum is released from the ovary it moves through the fallopian
tube (where it is fertilized by the sperm) into the uterus (the journey from the ovary to
the uterus takes about two or three days). The fallopian tube is the tube that connects
the ovary to the uterus. The sperm is the male cell. If the ovum is not fertilized the lining
breaks down and passes out of the body. This is the bleeding that women experience as
a menstrual period.
3.) Role of Genetics
1.) At the moment of conception, every human baby receives 46 chromosomes. A
chromosome is a tiny threadlike structure in the nucleus of every cell.
2.) A gene is a unit that determines a human’s inherited characteristics. The complete
blueprint for the creation of a person is called a genome.
3.) Dominant/Recessive Genes- A dominant gene is a stronger gene. The recessive
gene is a weaker gene.
4.) Sex chromosomes- Sex chromosomes come in two types- X and Y. Each ovum in the
woman’s ovaries carries an X chromosome. Each sperm cell in the man’s body
carries either an X or Y chromosome. If the sperm that fertilizes the egg carries an X
chromosome, the child will receive X chromosomes from each parent resulting in a
girl. A child with the XY combination will be a boy.
5.) Multiple Births-When the sperm fertilizes a woman’s ovum, the cell begins to divide
right away. When a woman gives birth to more than one child at a time, it is called
a multiple birth.
A.) Identical Twins- As the cells continue to divide, the mass of cells may split in
half, creating two separate cell masses. Each cell mass continues to divide
and grow into a separate embryo. Identical twins have very similar physical
characteristics and are always the same gender.
a.) Fraternal twins-Form when two eggs are released from the ovaries at the
same time and are fertilized by two different sperm. It is common for
fraternal twins to be opposite genders.
6.) Infertility- the inability to conceive a child.
A.) Adoption-A couple legally takes on all responsibilities and rights for raising,
loving, and caring for a child in need of a permanent home.
B.) Artificial Insemination-A doctor injects sperm into a woman’s uterus.
II.
C.) In Vitro Fertilization-This process is used to treat many cases of infertility, such
as when a woman has damaged fallopian tubes.
D.) Ovum Transfer- This procedure is similar to in vitro fertilization, except an ovum
has been donated by another woman.
E.) Surrogate Mother- A surrogate mother is a woman who becomes pregnant to
have a baby for another woman. The use of surrogate mothers or sperm and
ovum donors is considered controversial.
7.) Three Stages of Pregnancy-The baby’s development during pregnancy is called
prenatal development. If is often grouped into three stages called the germinal
stage, embryonic stage, and fetal stage.
A.) Germinal Stage-The first stage of the baby’s development. This stage includes
the formation of the zygote (fertilized egg). This stage lasts about two weeks
and includes cell division and implantation.
B.) Embryonic Stage-The second stage of pregnancy. The embryo is what the
developing baby is called from about the third week of pregnancy to the eighth
week. During this stage the organs and body systems are formed, the amniotic
sac filled with liquid forms and the placenta and umbilical cord forms. The liquid
that surrounds and protects the developing baby in the uterus is called amniotic
fluid. The placenta is a tissue that connects the developing baby to the uterus.
The umbilical cord is a long tube that connects the baby to the placenta. The
umbilical cord also takes carbon dioxide and other waste products away from
the baby.
C.) Fetal Stage-The fetal stage is the third and final stage of development. It is also
the longest stage. It begins around the eighth or ninth week of pregnancy and
lasts until birth. During this stage the developing baby is called a fetus. During
this stage the vocal cords develop and the digestive system and kidneys begin to
function. Spontaneous movements are possible by the end of the third month.
Problems in Prenatal Development
A.) Losing a Baby
1.) When a developing baby dies prior to the twentieth week of pregnancy the event is
called a miscarriage.
2.) If the baby dies AFTER the twentieth week, it is called a stillbirth.
B.) Birth Defects
1.) Causes of birth defects include: Factors in the environment, heredity factors, errors
in chromosomes, and a combination of environmental and heredity factors
2.) Environmental factors: The nutritional balance of a mother’s diet, any diseases or
infections the mother has during pregnancy, harmful substances the mother
consumes such as alcohol, over the counter medications, tobacco, and illegal drugs,
some medicines that benefit the mother but hurt the baby, air pollution, exposure
to x-rays and high levels of radiation or to certain chemicals such as solvents and
pesticides, especially early in pregnancy. Birth defects such as cleft lip, cleft palate
and spina bifida may be caused by a combination of hereditary and environmental
factors.
3.) Types of Birth Defects
a.) Cerebral Palsy-A variety of problems of the motor systems.
b.) Cleft Lip and Cleft Palate-A gap in the upper lip or palate that causes problems
with eating, swallowing, speech and appearance.
c.) Cystic Fibrosis-Affects respiratory and digestive systems.
d.) Down Syndrome-The presence of an extra chromosome 21.
e.) Muscular Dystrophy-A progressive weakness and shrinking of the muscles.
f.) PKU (phenylketonuria)-Defective recessive genes inherited from both parents.
g.) Sickle Cell Anemia-Malformed red blood cells that interfere with the supply of
oxygen to all parts of the body.
h.) Spina Bifida and Hydrocephalus-SB-incompletely formed spinal cord.
Hydrocephalus-excess of fluid surrounds the brain.
i.) Tay-Sachs Disease-The body cannot process and use certain fats.
4.) Prevention and Diagnosis of Birth Defects
A.) Genetic Counseling-meeting with a counselor to assess your risk of having a
child with a birth defect that is caused by a defect in the genes.
B.) Prenatal Tests
1.) Alpha-fetoprotein (AFP)-Abnormal AFP levels can indicate a possible birth
defect.
2.) Ultrasound-Uses sound waves to make a video image of an unborn baby.
3.) Amniocentesis-The process of withdrawing a sample of the amniotic fluid
surrounding the unborn baby.
4.) Chronic Villi Sampling-A prenatal test that uses the sample of the tissue
from the membrane that encases the fetus to check for specific birth
defects. One advantage is that it can be done much earlier in the pregnancy
than amniocentesis.
5.) Avoiding dangers to the Baby
A.) Alcohol- Fetal alcohol syndrome (FAS) is an incurable condition found in
some children of mothers who consumed alcohol during pregnancy.
B.) Prescriptions Drugs and Over-the-Counter Drugs-An expectant mother should
check with her doctor every time she considers using any type of medication,
vitamin or herbal supplement. There is no such thing as a completely safe drug
for a developing fetus.
C.) Caffeine-Caffeine passes easily from the mother to the fetus through the
placenta. It increases fetal heart rate and movement in the baby. It has been
associated with an increased risk of miscarriage, premature birth, and low birth
weight. Caffeine can draw fluid and calcium out of the body and may interfere
with the absorption of iron. It can also worsen mood swings and keep the
mother from getting the rest she needs.
D.) Tobacco-Can cause low birth weight in babies and premature birth. Smoking is
also linked to respiratory infections and allergies among children after they are
born.
E.) Illegal Drugs-Should never be used and can have devastating effects for an
unborn baby.
6.) Environmental Hazards
A.) X-rays-Present a potential danger to the unborn baby. Radiation from X-rays, or
from other sources, can cause birth defects.
B.) Hazardous Substances and Chemicals- Women should be careful around hazardous
substances such as paint, pesticides used to exterminate bugs, lead (in water and
paint), carbon monoxide, mercury (found in fish such as swordfish and shark), and
solvents (paint thinners, and formaldehyde.
7.) Diseases and Infections
A.) Rubella-If a pregnant woman contracts rubella, also known as German measles, it
can cause severe birth defects, blindness, deafness, heart disease and metal
retardation.
B.) Toxoplasmosis-is an infection caused by a parasite (found in raw meat and a cat’s
litter box).
8.) Sexually Transmitted Infections
A.) Syphilis-Can cause a skin rash, lesions, bone or facial deformities, deafness, or
brain damage. Babies will develop anemia, jaundice, or pneumonia in the first
few months of life.
B.) AIDS-If the doctor knows that the pregnant woman has AIDS or the virus that
causes it, special steps can be taken to reduce the baby’s exposure to the disease.
C.) Genital Herpes-Herpes simplex can cause the infant to be born with a brain
infection or mental retardation. Some babies die from the herpes simplex
infection. In most cases the infection is transmitted to the newborn during the
birth process.