Chapter 4:
Prenatal development, birth, and newborns’
readiness for life.
Dr. Pelaez
From conception to birth
• Prenatal development is divided into 3
major phases:
– Germinal period
– Embryonic period
– Fetal period
Germinal Period
• From conception to implantation (about 14
days).
• Zygote moves toward uterus through
fallopian tube
• Implantation occurs
• Support system develops (4 structures)
Embryonic period
•
•
•
•
•
Lasts from week 3 to week 8.
Neural tube development begins.
Heart begins to beat
Grows about 1/30 inches per day.
External body structures form (ears, limbs,
eyes)
Fetal period
• Lasts from week 9 to term.
• By end of month 3, sex can be detected on
ultrasound
• Neural and muscular systems continue to
develop
• By second trimester (month 5-6), covered by
vernix & lanugo (substance that protects fetal
skin & fine hair which helps vernix to stick to
body).
• Third trimester (weeks 25-38) involve rapid
growth and maturity of all organ systems.
Teratogens
• External agents such as viruses, drugs,
and radiation that can be harmful to
developing embryo or fetus.
• Sensitive periods
• Long-term effects depend on the quality of
postnatal environment
Maternal diseases
• Diseases capable of passing through
placenta and damage embryo/fetus
• Rubella. 60-85% of babies exposed will
have birth defects.
• STD’s (AIDS, herpes, syphilis).
• Toxoplasmosis
• Influenza
• Malaria
• Tuberculosis
Drugs
• Drugs taken by mother can have harmful effects
on children: (low birth weight, heart defects,
brain & neurological defects, and death).
• Thalidomide
• Diethylstilbestrol (DES)
• Alcohol
• Cigarettes
• Illegal, prescription, and over the counter drugs
Environmental hazards
• Environmental hazards that may cause
low birth weight, miscarriages, or genetic
defects to embryo/fetus:
• Radiation
• Lead
• Zinc
• Mercury
• Other harsh chemicals
Maternal characteristics
• Maternal behavior can affect the outcome
of her pregnancy
• Mother’s diet
• Mother’s emotional well-being
• Mother’s age
Birth Process
• Perinatal environment: environment surrounding
birth; includes influences such as drugs given to
the mother, delivery practices, and the social
environment.
• 3 stage process:
1. first stage of labor: uterine contractions. Lasts
about 3-8 hours.
2. second stage of labor: fetus moves through
birth canal & emerges from mother’s body.
3. third stage of labor: expulsion of the placenta
Three stages of child birth.
Social environment at birth
• First 12-16 hours are a sensitive period of
emotional bonding.
• Postpartum depression may inhibit
emotional bonding.
• Early father-infant interactions may make
fathers feel more a part of the family.
Assessing the baby’s condition
• Apgar test: assess newborn heart rate,
color, respiration, muscle tone, and
reflexes.
• Neonatal Behavioral Scale (NBAS):
assess neonate’s neurological integrity
and responsiveness to environmental
stimuli.
– NBAS administered a few days after birth
– Assess 20 reflexes.
– Low scores may indicate brain damage or other
neurological problems
Birth complications
• Anoxia
• Oxygen deprivation
• Breech position
• Rh factor
• Premature delivery
• Preterm: born 3 weeks or more before term.
• Small for date babies
• Low birth weight
• Small for date: slow growth
• Under 5 lbs
• May experience respiratory distress syndrome
Readiness for life
• Healthy newborns display a number of
reflexes.
• Survival reflexes: breathing, sucking &
swallowing
• Primitive reflexes (disappear during first
year of life): babinksi reflex, swimming,
stepping reflex
Readiness for life continued
• Infant states.
–
–
–
–
–
–
Regular sleep: 8-9 hours/day
Irregular sleep: 8-9 hours/day
Drowsiness: ½-3 hours/day
Alert inactivity: 2-3 hours/day
Alert activity: 1-3 hours/day
Crying: 1-3 hours/day
Reflexes in full term infants
Table
4.6
Pg. 135