Chapter 4: PRENATAL DEVELOPMENT AND BIRTH
The Course of Prenatal Development
The course of prenatal development last approximately 266 days,
beginning with fertilization and ending with birth.
Three periods of prenatal development:
1. Germinal Period – takes place in the first two weeks after
conception. It includes the creation of the zygote, continued cell
division, and the attachment of the zygote to the uterine wall.
Blastocyst – the inner mass of cells that develops during the
germinal period. These cells later develop into the embryo.
Trophoblast – an outer layer of cells that develops in the germinal
period. These cells will become part of the placenta.
Implantation – the attachment of the blastocyst to the uterine
wall, takes place about 10 to 14 days after conception.
2. Embryonic Period – occurs from two to eight weeks after
conception. During the embryonic period, the rate of cell
differentiation intensifies, support systems for the cells form, and
Placenta – a disk-shaped group of tissues in which small blood
vessels from the mother and offspring intertwine but do not join.
Umbilical cord – contains two arteries and one vein; connects the
baby to the placenta.
Amnion – the life-support system that is a bag or envelope
containing a clear fluid in which the developing embryo floats.
Organogenesis – organ formation that takes place during the first
two months of prenatal development.
After the blastocyst attaches to the uterine wall, the mass of cells
is called an embryo and the three layers of cells are formed:
o Endoderm – inner layer of cells, which will develop into
the digestive and respiratory systems.
o Ectoderm – outermost layer, which will become the
nervous system, sensory receptors (ears, nose, and
eyes, for example), and skin parts (hair and nails, for
o Mesoderm – middle layer, which will become the
circulatory system, bones, muscles, excretory system,
and reproductive system.
3. Fetal Period – begins two months after conception and lasts for
seven months, on average.
TERATOLOGY AND HAZARDS TO PRENATAL DEVELOPMENT:
Teratogen – from the Greek word tera, meaning “monster.” Any agent that
causes a birth defect. The field of study that investigates the causes of birth
defects is called teratology.
The dose, the time of exposure to a particular agent, and genetic
susceptibility influence the severity of the damage to an unborn child and the
type of defect that occurs.
Prescription and Nonprescription Drugs
o Prescription drugs that can function as teratogens
include anitbiotics; some antidepressants; certain
hormones; and Accutane (prescribed for acne)
o Nonprescription drugs that can be harmful include
diet pills, aspirin, and caffeine.
Psychoactive Drugs – drugs that act on the nervous system to
alter states of consciousness, modify perceptions, and change
Fetal alcohol syndrome – a cluster of
abnormalities that appears in the offspring
of mothers who drink alcohol heavily during
Reduced birth weight, length, and head
circumference; impaired motor
development; lower arousal; less effective
self-regulation, higher excitability; lower
quality of reflexes; impaired information
processing and language development;
poor attentional skills; impaired processing
of auditory information after birth; and
neurological and cognitive deficits.
Impaired attention; smaller babies; learning
and memory difficulties at age 11.
Behavioral difficulties and attention deficits
Incompatible Blood Types
Gene mutation, chromosomal
abnormalities, microencephaly, mental
retardation, and leukemia
o Environmental pollutants and toxic wastes: carbon
monoxide, mercury, lead
o Manufacturing chemicals known as PCBs
Visual discrimination and short term
o Sauna or hot tubs
Fever, birth defects, even fetal deaths
Other Maternal factors
o Infectious disease
Rubella (German measles)
Mental retardation; blindness;
deafness; heart problems
Syphilis (a sexually transmitted infection)
Damages organs after they have
formed; eye lesions; skin lesions;
problems in central nervous
system and gastrointestinal
May die or brain damage
Destroys the body’s immune
o Emotional states and stress
o Maternal age
Infants born to adolescents are often
Infants born to 35 years and older have
increased risk for low birth weight and for
o Exposure to lead, radiation, certain pesticides, and
petrochemicals may cause abnormalities in the sperm
that lead to miscarriage or diseases, such as childhood
o Low vitamin C
Cancer and birth defects
Low birth weights and cancer
Birth defects including Down Syndrome,
dwarfism, marfan sysndrome, which
involves head and limb deformities.
The Birth Process
Stages of Birth
o First stage lasts an average of 12 to 24 hours; it is the
longest of the three stages; Uterine contractions are 15
to 20 minutes apart at the beginning and last up to a
o Second birth stage begins when the baby’s head starts
to move through the cervix and the birth canal. Lasts
approximately 1 ½ hours.
o Afterbirth is the third stage, at which time the
placenta, umbilical cord, and other membranes are
detached and expelled. The shortest of the three,
lasting only minutes.
The Transition from fetus to Newborn
o Being born involves considerable stress for the baby.
The first breaths may be the hardest ones an individual
o Childbirth Setting and Attendants
o Methods of Childbirth
Analgesia – used to relieve pain.
barbiturates, and narcotics (such
Anesthesia – used in late first-
stage labor and during expulsion
of the baby to block sensation in
an area of the body or to block
consciousness. (epidural block,
regional anesthesia that numbs
the woman’s body from the
Oxytocics – synthetic hormones
that are used to stimulate
contractions. (Pitocin, most
Natural childbirth – 1914, Grantley Dick-
Read: Its purpose is to reduce the mother’s
pain by decreasing her fear through
education about childbirth and by teaching
her to use breathing methods and
relaxation techniques during delivery.
Prepared childbirth – Ferdinand Lamaze:
similar to natural childbirth but includes a
special breathing technique to control
pushing in the final stages of labor, as well
as a more detailed anatomy and physiology
course. Lamaze method, is where the
pregnant woman’s husband or a friend
usually serves as a coach, who attends
childbirth classes with her and helps her
with her breathing and relaxation during
Cesarean delivery – the baby is removed
from the mother’s uterus through an
incision made in her abdomen. Sometimes
known as cesarean section or C-section. A
cesarean section is usually performed if the
baby is in a breech position, which causes
the baby’s buttocks to be the first part to
emerge from the vagina. Cesarean
deliveries also are performed if the baby is
lying crosswise in the uterus, if the baby’s
head is too large to pass through the
mother’s pelvis, if the baby develops
complications, or if the mother is bleeding
Low Birth Weight Infants: weigh less than 5 ½ pounds at birth.
Preterm infants: infants born three weeks or more before the
pregnancy has reached its full term.
Small for date infants: also called small for gestational age
infants, these infants’ birth weights are below normal when the
length of pregnancy is considered. It may be preterm or full term.
o Kangaroo care: a way of holding a preterm infant so
that there is skin-to-skin contact. Advantages: stabilize
the heartbeat, temperature, and breathing; the
mothers have more success with breastfeeding and
improve their milk supply; have longer periods of
sleep, gain more weight, decrease crying, have longer
periods of alertness, and earlier hospital discharge.
o Infant massage: might play in improving the
developmental outcome of preterm infants.
Measures of Neonatal Health and Responsiveness
Apgar Scale: A widely used method to assess the health of
newborns at one and five minutes after birth. It evaluates infant’s
heart rate, respiratory effort, muscle tone, body color, and reflex
Brazelton Neonatal Behavioral Assessment Scale: A test
performed within 24 to 36 hours after birth to assess newborns’
neurological development, reflexes, and reactions to people.
Score 0 1 2
Heart rate Absent Slow—less than
100 beats per
No breathing for
more than 1
Muscle tone Limp and Flaccid Weak, inactive,
but some flexion
Body color Blue and pale Body pink, but
Entire body pink
Reflex Irritability No response Grimace Coughing,
The Apgar Scale
Postpartum Period: The period after childbirth when the mother adjusts,
both physically and psychologically, to the process of childbirth. This period
lasts for about six weeks or until her body has completed its adjustment and
returned to a near prepregnant state.
Involution: the process by which the uterus returns to its
prepregnant size five or six weeks after birth. Immediately
following birth, the uterus weighs 2 to 3 ½ ounces.
The woman will probably begin menstruating again in four to
eight weeks if she is not breastfeeding. If she is breastfeeding, she
might not menstruate for several months to a year or more,
though ovulation can occur during this time.
Physicians often recommend that women refrain from having
sexual intercourse for approximately six weeks following the birth
of the baby.
The mother can begin some exercises as soon as one hour after
delivery such as relaxation techniques and slow breathing.
Emotional and Psychological Adjustments
Here are some signs that can indicate a need for professional
counseling about postpartum adaptation:
o Excessive worrying
o Extreme changes in appetite
o Crying spells
o Inability to sleep
Postpartum depression: characteristics of women who have such
strong feelings of sadness, anxiety, or despair that they have
trouble coping with daily tasks in the postpartum period.
Bonding: the formation of a close connection, especially a
physical bond between parents and their newborn, in the period
shortly after birth.
1. What can be done to convince women who are pregnant not to
smoke or drink? Consider the role of health-care providers, the
role of insurance companies, and specific programs targeted at
women who are pregnant.
2. If you are a female, which birth strategy do you prefer? Why? If
you are a male, how involved would you want to be in helping
your partner through pregnancy and the birth of your baby?
3. If you are a female, what can you do to adjust effectively in the
postpartum period? If you are a male, what can you do to help in
the postpartum period?
Santrock, J.W. (2006). Life-Span Perspective.10th Edition. McGraw-Hill. New York.
Mrs. Maria Angela L. Diopol