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Prenatal Development

Prenatal Development. Chapter 2. Biological Beginnings: Conception. Ova are released from the ovaries and travel down the fallopian tubes, where conception occurs. Development begins at conception. Males produce an average of 300 million sperm per day. Only 300-500 reach the ovum.

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Prenatal Development

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  1. Prenatal Development Chapter 2

  2. Biological Beginnings:Conception Ova are released from the ovaries and travel down the fallopian tubes, where conception occurs. Development begins at conception. Males produce an average of 300 million sperm per day. Only 300-500 reach the ovum. Sperm can live for 6 days and ova for one.

  3. 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)

  4. Period of the Zygote (Germinal) 4th day – blastocyst, hollow, fluid filled ball (60-70 cells) Inside, embryonic disk will become new organism Outside, troboblast, protective covering

  5. 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

  6. Troboblast will form the amnion (fluid sac which regulates temperature and forms a cushion) Will also form the chorion, from which fingerlike villi or blood vessels emerge and the placenta forms as they burrow into the uterine lining. Period of the Zygote (Germinal)

  7. Umbilical cord connects the growing organism to the placenta It has one vein and two arteries The mother’s and embryo’s blood will not mix directly (red blood cells, bacteria, hormones, maternal waste are filtered) Embryonic Period – 3rd week after conception

  8. Embryonic disk forms: Ectoderm – skin and nervous system Mesoderm – muscles, skeleton, circulatory system Endoderm – digestive system, lungs, urinary tract, glands Embryonic Period – 3rd week after conception

  9. 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.

  10. 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

  11. 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

  12. Mother can feel movements Can hear heartbeat with ordinary stethoscope 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

  13. 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

  14. 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

  15. 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

  16. 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)

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

  18. 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

  19. Cocaine Heroin/methodone Prematurity, LBW, breathing difficulties, physical defects, infant death, stressed and drug addicted Marijuana Smaller head size, disturbed sleep, inattention in infancy Teratogens – Illegal Drugs

  20. 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 - tobacco

  21. 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

  22. 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

  23. Environmental Teratogens Radiation (Hiroshima, Nagasaki, Chernobyl) Miscarriages, babies with underdeveloped brains, physical deformities, slow growth Mercury – 1950s Minamata, Japan – resulting brain damage in children Lead – prematurity, LBW, brain damage, physical defects PCBs (insulators for electrical equipment) – lower intelligence

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

  25. Nutrition Emotional stress Maternal age & previous births Other Maternal Factors

  26. 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

  27. 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)?

  28. The Birth Process Dilation and effacement (of the cervix)(Labor) At transition a clear channel from the uterus to the vagina is formed (birth canal) Birth of the baby (Delivery) 20-50 minutes Delivery of the placenta (afterbirth) (5-10 minutes)

  29. Birth Complications and Medical Interventions Anoxia Breech position Cerebral palsy Fetal monitors Medication (90-95% of births) Analgesics, anesthetics Cesarean delivery (30% of births)

  30. 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

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

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

  33. 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

  34. Apgar (1 & 5 minutes after birth) 5 characteristics Heart rate, respiratory effort, reflex irritability, muscle tone, color) 0,1,or 2 points on each Total score 7+, good physical condition 4-6, baby requires assistance 3-, infant in serious danger, requires emergency attention

  35. The Newborn - Arousal Sleep 18-20 hours per day 50% is REM sleep SIDS (Sudden Infant Death Syndrome)

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