Prenatal Development

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. 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 Period of the Fetus – Growth and Finishing Phase

6. 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 Period of the Fetus – Growth and Finishing Phase – 3rd Month

7. 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 Period of the Fetus – Growth and Finishing Phase – 2nd Trimester

8. The current age of viability (at which the fetus can survive outside the mother) is about 22 weeks 50% survive at about 25 - 26 weeks (6 months) 95% survive at 31+ weeks Period of the Fetus – Growth and Finishing Phase-Age of Viability

9. 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 Problems with Preemies

10. 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 (headdown) Fetal Period – 3rd Trimester

11. 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) Teratogens (Monsters)

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

13. 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 Teratogens - Drugs

14. 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. Teratogens – Why does it do this – tobacco?

15. 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. Teratogens - Alcohol

16. 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. Teratogens - Alcohol

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

18. 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. Prenatal Health Care

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