04-PRENATAL
DEVELOPMENT AND
BIRTH
Prenatal development
Pregnancy confirmation
• Can not be confirmed by blood or urine tests until the
zygote implants in the uterus (about 10 days after
conception).
Prenatal Development
• Germinal - 1st 2 weeks
• Embryo – Week 3 to 8 (2 months)
• Fetus – Week 9 to birth
Germinal period
• First 2 weeks
• Conception
• Zygote
• Implantation
Embryo
• Week 3 – 8 (2 months)
• First - “Primitive streak” develops = neural tube = brain &
spinal column
• 4th. Week
• Head takes shape
• Early heart begins to pulsate
• 5th. Week
• Arm & leg buds develop
• Webbed fingers and toes develop
• 8th. Week
• 1 inch long
• Has all basic body parts and organs (except sex organs)
• Embryo – 4 weeks
• Embryo – 5 Weeks
• Embryo – 7 weeks
• Embryo – 8 Weeks
Fetus (9 weeks – Birth)
9th. Week
• Male gene triggers development of male organs
• If not, female organs develop
Fourth, fifth, sixth months
• Heartbeat becomes stronger
• Digestive and excretory systems develop
• New neurons & synapses develop
• Up to one 500,000 brain cells per minute are created
• Age of viability
• Can possibly survive outside the mother (with intensive medical
care)
• 22 weeks
Fetus (9 weeks - birth)
• Final three months
• Lungs begin to expand and contract (fetal respiration)
• Breathe using amniotic fluid as a substitute for air
• Fetus
• Grows and moves more
• Startles and kicks at a loud noise
• Becomes used to mother’s heartbeat and voice
• Responds if mother is fearful or anxious
Birth
• Labor
• 12 hrs. – first child
• Stages of labor
• 1st. = Cervical dilation
• 2nd. = Crowning
• About 31% of zygotes survive to be born
• Birth in U.S.
• Birth in Peru
• Birthing chair - Egypt
Apgar Scale
• Color
• Heart
• Reflex
• Muscle
• Breathing (Respiration)
• Done twice – 1 & 5 minutes after birth to determine if
immediate medical care is needed
• Score = 0,1,2 for each item
• Total of 7 or above is desired
Problems and Solutions
Teratogens:
(Items increasing prenatal abnormalities)
• Types
• Substances (drugs, pollution)
• Conditions (Stress or malnutrition)
• Teratogens = Physical defects
• Cleft palate
• Thalidomide babies (deformed limbs)
Behavioral teratogens = Behavioral
defects
• Hyperactivity
• Antisocial
• Learning-disabled
Teratogens:
Critical factors
• Timing
• Some only cause damage during critical periods
• When organ or body part is most vulnerable
• Before pregnancy
• Avoid drugs (e.g. alcohol)
• Fetal alcohol syndrome
• Better diet
• Immunizations
• Problem – Half of births are unplanned
• Threshold effect
• Some are harmless until they “cross the threshold” and become
harmful
• Alcohol, tobacco, and marijuana do more harm in combination
• This lowers the threshold for each
• Genes – May increase birth defects
Low birth weight
• Causes
• Born preterm
• Born small for gestational age (SGA)
• Maternal or fetal illness
• Drug use
• Every psychoactive drug
• Tobacco (Most prevalent cause)
• Malnutrition
• Consequences
• Infant death
• Thinking (cognitive) problems
• Seeing and hearing problems
• In adulthood - higher rates of:
• Obesity
• Heart disease
• Diabetes
Newborn reflexes
• Reflex = involuntary response to a stimulus
• Reflexes that aid survival
• Breathing – Maintains oxygen
• Shivering – Maintains temperature
• Sucking – Manages feeding
• Rooting – Searching for a nipple
• Reflexes that show the state of brain and body functions
• Babinski reflex – Toes fan upward when feet are stroked
• Stepping reflex
• Swimming reflex
• Palmer grasping reflex
• Moro reflex - Being startled
• Sucking reflex
• Grasping reflex
• Stepping reflex