1. Prenatal Development
Chapter 2

2. The Three Periods of Pregnancy
Germinal (Period of the Zygote)
First two weeks, ends with implantation
Embryonic Period
2-8 weeks, organogenesis
Fetal Period
9 weeks – birth (all trimesters)

3. Period of the Zygote (Germinal)
Within about 1 week of conception, cell differentiation begins
Implants (attaches to the uterine wall) on the 10th to 14th day

4. Embryonic Period (2-8 weeks) - Organogenesis
Neural tube develops first, will become brain and spinal cord – rapid neuron growth, weak brain waves
Next, heart begins to pump blood
The basic structure of all the organ systems grows
Eyes, ears, nose, jaw, neck, arm and leg buds
At the end of this period, it weighs less than one ounce, about one inch long.

5. Period of the Fetus – Growth and Finishing Phase
Called a fetus from the 8th week until birth
Fetus means fully-formed human being because all organ systems are now in place
During the 3rd month (12-16 weeks) it will have coordinated movements, be able to roll over in the amniotic fluid
Hair, eyelashes, eyebrows will grow

6. Period of the Fetus – Growth and Finishing Phase – 3rd Month
By 12th week external genitals well formed, also fingernails, toenails, tooth buds, eyelids
Heartbeat can be heard with a special stethoscope
End of 3 months, 3 inches, 3 ounces
The fetus can kick, bend its arms, form a fist, curl its toes, open its mouth, suck its thumb, smile & swallow

7. Period of the Fetus – Growth and Finishing Phase – 2nd Trimester
Neurogenesis, which begins earlier, proceeds rapidly (250,000 neurons per minute)
At 20-weeks can be stimulated/irritated by sound; will shield eyes during fetoscopy

8. Period of the Fetus – Growth and Finishing Phase-Age of Viability
The current age of viability (at which the fetus can survive outside the mother) is about 22 weeks
50% survive at about weeks (6 months)
95% survive at 31+ weeks

9. Problems with Preemies
Depends upon gestational age at birth
Breathing
Hyaline membrane disease
Regulating blood oxygen levels
Apnea
Temperature regulation
Feeding
Parenting – 47% faster weight gain & brain development with touch
Kangaroo care

10. Fetal Period – 3rd Trimester
Begins sleep-wake pattern
Responsiveness, can feel pain after 22 weeks
React to sounds
Prefer mother’s voice
Adds fat (5 pounds)
Receives antibodies
Assumes birth position (head down)

11. Teratogens (Monsters)
Any environmental agent that causes prenatal damage (leading to birth defects)
Types – drugs, diseases, radiation, environmental pollutants
Factors – dose, resilience (heredity), number of teratogens, gestational age at exposure (embryonic period worst)

12. Teratogens - Drugs Examples Thalidomide – 7000 infants affected
Limbs, heart, ears, kidneys, genitals
DES (diethylstilbestrol) – reproductive problems in adult children (cancer; abnormalities in reproductive organs)

13. Teratogens - Drugs
Don’t take anything without consulting your obstetrician
Examples
Aspirin – may be associated with LBW, infant death, lower IQ, poor motor development
Caffeine – LBW, miscarriage, irritable infants

14. Teratogens – Why does it do this – tobacco?
Nicotine constricts blood vessels and lessens blood flow to the uterus, causes the placenta to grow abnormally, reduces the transfer of nutrients, raises the carbon monoxide concentration in the blood stream which may damage the central nervous system
Smoking during pregnancy is associated with LBW and increased frequency of prematurity, impaired breathing during sleep, infant death and childhood cancer.

15. Teratogens - Alcohol
Fetal Alcohol Syndrome (FAS/FAE) is the leading preventable cause of mental retardation.
Other symptoms include impaired motor coordination, attention, memory & language; slow physical growth & overactivity.
Facial abnormalities include widely spaced eyes, short eyelid openings, thin upper lip, small head, small upturned nose.

16. Teratogens - Alcohol
Lesson – Women should avoid alcohol during pregnancy.
Alcohol inteferes with brain development – causing abnormalities in structure and function.
Oxygen needed for cell growth is taken from the fetus to metabolize alcohol.

17. Teratogens – Infectious diseases
Rubella
HIV/AIDS
Genital herpes
toxoplasmosis

18. Prenatal Health Care
18% of women in the U.S. wait until the second trimester, and 4% until the end to get care
Many of these are unmarried, adolescent, or poverty stricken.
Reasons include lack of insurance, ambivalent feelings, high risk behaviors, and lack of transportation.

19. Approaches to Childbirth
How much medical care/availability?
Should it be natural or prepared?
Lamaze, Bradley, hypnobirthing
How about the pain?
Epidural, walking/dual-spinal epidural
How about a midwife (or a doula)?

20. Low Birthweight Infants (LBW)
(Low)Birthweight is the best available predictor of infant survival & healthy development.
Low Birthweight Babies weigh less than 5.5 pounds.
1 of 14 American infants
More problems with inattention, overactivity, language delays, low IQ scores, and motor deficits

21. Low Birthweight Infants (LBW)
Preterm babies – born early (35/8 or fewer weeks) may be weight appropriate
Small-for-date babies may have more serious problems.

22. Why so many preemies? 50% unknown Mother’s reproductive system
Immaturity; twins
Correlation with Father’s age (older fathers)

23. Premature Infants Low birthweight Very low birthweight -, 1250 grams
Many will end up normal
A higher frequency will have minor problems that show up later