1. Prenatal Development and Birth
Chapter 4

2. Periods of Prenatal Development
The Period of the Zygote
Zygote  blastocyst
Cell differentiation
% of blastocysts that fail to implant?

3. Periods of Prenatal Development
The Period of the Zygote (con’t)
Outer layer of blastocyst develops into:
Amnion
Chorion
Placenta
Umbilical cord
**note that these structures actually develop during the period of the embryo

4. Periods of Prenatal Development
The Period of the Embryo
From implantation (week 3) to week 8
Embryonic disk is already differentiating into:
Ectoderm (nervous system, skin, hair, sensory receptors
Mesoderm (muscles, bones, circulatory system, reproductive system, excretory system)
Endoderm (digestive system, lungs, urinary tract, other internal organs)

5. Periods of Prenatal Development
The Period of the Embryo (con’t)
By 4th week, heart has formed and begun to beat
Becomes more human in appearance during 2nd month
Sexual differentiation during 7th – 8th weeks

9. Periods of Prenatal Development
The Period of the Fetus
Final 7 months of pregnancy
Fetus
Digestive and excretory systems functional
Sex detected by ultrasound by end of 3rd month
Kicks and movements strong enough to be felt
Organ systems mature rapidly during final 3 months

12. Periods of Prenatal Development
The Period of the Fetus (con’t)
Viable between weeks
Receives antibodies
Assume upside-down position in final weeks
Weight of head
Shape of uterus

16. Trends in Development
Cephalocaudal Trend
Proximodistal Trend

17. Teratogens Root word means “formation of monsters”
Harm isn’t always simple or straightforward
Amount and length of exposure
Genetic makeup of mother/baby
Presence of several negative factors

18. Teratogens Same defect  different teratogens
One teratogen  different defects
Some effects seen later

19. Teratogens
Age of baby
Sensitive period

21. Teratogens Paternal influences often overlooked
Direct and indirect effects
Second hand smoke
Chemicals
Cocaine can “hitchhike”
Smoking, alcohol, drug use  sperm
Diets low in vitamin C

22. Other Factors Exercise Nutrition Emotional stress
Rh blood incompatibility
Maternal/Paternal age
Older  less fertile, more risk of disorders
Younger  increased risk of prematurity, infant death

23. Other Factors
Infectious Diseases
Prenatal Care
Previous births

24. Perinatal Environment
Environment surrounding birth
Stages of childbirth
Contractions
Delivery
Afterbirth
Newborn appearance

25. Perinatal Environment
Assessing the Newborn
Apgar scale
1 minute and 5 minutes after birth

27. Perinatal Environment
Assessing the Newborn
Neonatal Behavioral Assessment Scale (NBAS)
Several days after birth
20 inborn reflexes
Reactions to comforting and social stimuli
Unresponsiveness may indicate neurological problems
Can be a parent teaching tool

28. Perinatal Environment
Complications
Anoxia
Severe  cerebral palsy, mental retardation
Mild  irritability, motor/cognitive delays
Chances have been reduced with fetal monitoring
Respiratory distress syndrome
Complicated delivery
Forceps
Cesarean
Medications

29. Preterm and Small-for-Date
Preterm = born more than 3 weeks early, but appropriate weight for time in womb
Small-for-Date = underweight due to slow fetal growth
Greater risk than preterm
Causes include smoking, drug use, stress, lack of prenatal care, multiple births, social support
Postterm = born after 42 weeks