1. Sex Chromosomes
•
•
•
•
•
•
XX = Female
XY = Male
XO = Female, Turner’s Syndrome
XXY = Male, Kleinfelter’s Syndrome
XYY = Male, Double Y Syndrome
Fragile X = Male or Female
Berch & Bender (1987); Berger, K. S. (2006); Doyle & Paludi (1998).
1
3. From Zygote to Newborn
• Prenatal development is divided into three
main periods:
– Germinal period (0-2 weeks)
– Embryonic period (3-8 weeks)
– Fetal period (9 weeks-birth)
3
4. Timing
• Pregnancy begins at conception
– Start of gestational age
– Obstetrician may use LMP – 14 days
before conception
• Length of pregnancy
– 266 days, 38 weeks, or 9 months
– LMP = 40 weeks
4
5. Timing
• Trimesters (3 mo.) vs. germinal,
embryonic, and fetal periods
• Due date
– Based on LMP
– 5% babies born on that date
– Full term = 3 weeks early or 2 weeks
late (preterm and post-term)
5
6. Germinal: The First 14 Days
• Germinal period:
– First two weeks of prenatal development after
conception
– Characterized by rapid cell division and the
beginning of cell differentiation
6
7. • Embryonic period:
– Approximately the third through eighth week after
conception
• all body structures, including internal organs,
begin to develop
• Fetal period:
– Stage of prenatal development from ninth week after
conception until birth, during which the organs grow
in size and mature in functioning
7
8. Germinal: The First 14 Days
• Implantation:
– process in which
developing organism
burrows into placenta that
lines uterus
• Placenta:
– organ that surrounds
developing embryo and
fetus, sustaining life via
the umbilical cord
8
9. Embryo: From the Third Through the Eighth Week
• Embryo: a developing human organism
from about the third through the eighth
week after conception
4 weeks ¼ in.
5 weeks
7 wks. <1 in.
8 wks. 1 in.
9
10. Fetus: From the Ninth Week Until Birth
• The developing organism is called a
fetus from the start of the ninth week
after conception until birth
10
11. The Third Month
• At the end of the third month, the fetus
has all its body parts
• Weighs approximately 3 ounces and is
about 3 inches long
11
12. • In the fourth, fifth and
sixth months:
– Heartbeat becomes
stronger
– Cardiovascular system
becomes more active
– Brain increases about six
times in size
12
13. • Age of viability: age at which a fetus
can survive outside the mother’s uterus if
specialized medical care is available
– About 22 weeks after conception
13
14. Final 3 Months
• Brain waves indicate responsiveness
• Lungs expand and contract, using the
amniotic fluid as a substitute for air
• Heart valves, arteries, and veins circulate the
fetal blood
14
16. Risk Reduction
• Teratogens: agents and conditions that can
– Harm the prenatal brain
– Impair the future child’s intellectual and emotional
functioning
16
18. – Teratology: science of risk analysis, the
study of birth defects
– Risk analysis: to determine likelihood of
harm, science of weighing the potential effects
of a particular:
– event
– substance
– experience
18
20. – Threshold effect: situation in which a
certain teratogen is relatively harmless in
small doses but harmful once exposure
reaches certain level (the threshold)
• Vitamin A beneficial in low doses, dangerous
in high doses
– Interaction effect: result of a
combination of teratogens
• Alcohol, tobacco, and marijuana
20
21. Genetic Vulnerability
– Dizygotic twins, exposed to same teratogens
but have only half their genes in common, are
born with different abnormalities
• Suggests both protective and vulnerable genes
– Cleft lip, cleft palate, club foot more common
in some families
• Suggests genetic vulnerability
– Neural tube defects
21
22. Protective Measures
• Impact of teratogens cannot be predicted
before mid-pregnancy
• Some pregnant women are exposed to the
tetragons with no evident harm
• Some defects occur even though the woman
avoids all known tetragons while pregnant
22
23. A View From Science
• Alcohol in high doses is a proven teratogen
• 40 years ago drinking during pregnancy was
believed to be harmless
• Obstetricians noted that some patients who
drank heavily while they were pregnant had
babies with distorted faces
23
24. • Fetal alcohol syndrome (FAS) : cluster of
birth defects
–
–
–
–
Abnormal facial characteristics
Slow physical growth
Cognitive delays or deficits
Impulsiveness
• Fetal alcohol effects (FAE) : condition in
which child has been exposed to alcohol
before birth
– Some signs of fetal alcohol syndrome but does not
meet all the criteria
24
25. Benefits of Prenatal Care
• Tests done during pregnancy can diagnose
problems early on, and remedies can be put
in place in some instances
• Sonogram: image of unborn fetus (or an
internal organ) produced by high-frequency
sound waves (ultrasound)
25
26. • For full-term fetus and a healthy mother, birth
can be simple and quick
26
27. The Newborn’s First Minutes
• Most newborns begin to breathe as soon as their
head emerges.
– first breath causes infant’s color to change
– eyes open wide
– the tiny fingers grab
– toes stretch and retract
– mucus in the baby’s throat is removed
– umbilical cord is cut to detach the placenta
– placenta is expelled
27
28. Apgar scale: quick assessment of newborn’s
condition including:
–
–
–
–
–
the baby’s color
heart rate
reflexes
muscle tone
respiratory effort
28
30. Birth In Developing Nations
•
•
•
In the U.S. only 1% of births take place at
home.
Worldwide most births occur at home
Doula- a woman who helps with the birth
process
- Also helps with breastfeeding and newborn care
30
31. Anoxia
• Anoxia:
– lack of oxygen that can cause brain damage or
death to the baby
– means “no oxygen”
• Cerebral palsy:
– disorder that results from damage to brain’s motor
centers
– People with cerebral palsy have difficulty with
muscle control, so their speech and body
movements are impaired.
31
32. Low Birthweight (LBW)
• Average weight of a newborn is 7½ lbs.
– Low birthweight (LBW): a body weight at
birth of less than 5½ lbs.
– Very low birthweight (VLBW): a body
weight at birth of less than 3 lbs, 5oz.
– Extremely low birthweight (ELBW): a
body weight at birth of less than 2 lbs, 3 oz.
32
33. • Preterm birth: occurs 3 or more weeks before
full 38 weeks of a typical pregnancy
– Preterm babies are typically (but not always)
LBW because they miss final weeks of weight
gain
– Small for dates or small for gestational age
(SGA)- birth weight is lower than expected
given the time of conception
33
34. Social Support
• The developing person is affected by quality
of:
–
–
–
–
medical care
education
culture
social support
• Fathers and other relatives, neighbors, cultures,
and, clinics can reduce risk of birth
complications
34
35. Mothers, Fathers, and a Good Start
• Birth complications can have a lingering impact
on the new family, depending partly on:
– sensitivity of hospital care
– the home
• To reduce stress on an infant who has to stay
in the hospital, parents are encouraged to help
with early caregiving.
35
36. • Kangaroo care: form of
child care in which the
mother of a low-birthweight
infant spends at least an
hour a day holding the baby
between her breast, like a
kangaroo
36
37. Help from Fathers
• Fathers can be crucial in the effort to produce a
healthy baby.
• Supportive father-to-be helps a mother-to-be:
– stay healthy
– well nourished
– drug-free
37
38. • Parental alliance: cooperation between a
mother and a father based on mutual
commitment to their children
• Parents agree to support each other in their
shared parental roles
38
39. Postpartum Depression
• New mother’s feelings of inadequacy and
sadness in days and weeks after giving birth
including:
– irritability
– eating disruptions
– sadness
– feeling overwhelmed and inadequate
• Affects 10-15% of women
39
One X is essential to life. Turner’s syndrome: female, short and immature in appearance, webbed necks, eyelid folds, receding chcins, broad chest. Sterile (missing the X that directs development of ovaries); interest in “feminine” activities. Estrogen therapy to develops secondary sex characteristics. Intellectually fine, even above average. Kleinfelter’s: 1-2/1000 males; average height, long limbs, high pitched voice, sterile, sometimes cognitively imparierd. High prison population – minor crimes, more frequent arrests, not predisposition to criminal activity.
YY: 1/1000 males; even taller than males with Kleinfelter’s Syndrome, also have a high crime rate – nonviiolent (theft and larceny); intellectual impairment.
Fragile X: 1/3 females cog. Impair; 20% males normal, 33% impaired, rest severely impaired. Fragile-X syndrome is the most common cause of inherited mental impairment. It affects about one in 5000 boys and about one in 2500 girls. As well as learning difficulties, people with Fragile-X may have other symptoms, including anxiety and hyperactivity. Boys are usually more severely affected than girls. Diagnosis of Fragile-X syndrome is important, as special education and therapy can help affected children.
LMP – date of last menstrual period
Not yet nourished by the mother so does not increase in size for 10 days. At 10 days, implantation in the uterus occurs. 60% of natural and 70% of in vitro conceptions FAIL to implant.
Structural information
About 20% of all embryos are aborted spontaneously , most often because of chromosomal abnormalities. We begin to see the primitive streak, which will become the neural tube 22 days after conception. The neural tube becomes the central nervous system (brain and spinal cord). At 5 weeks we begin to see buds of arms and legs. At 52 and 54 days after conception the fingers and toes separate. At the 7th week, the embryo has eyes, nose and digestive system and the beginning of toes. At the 8th week, the embryo weighs about 1/13 ounce, 1 in. long. All the basic organs and body parts. At this point, the embryo has an indifferent gonad.
During the fetal period the fetus develops from tiny, sexless creature to a 7 1/2-pound, 20-inch boy or girl. If the embryo is male, in the third month a gene on the Y chromosome commands the development of male sex organs. Female organs are the default mode of no command is given. By week 12, the genitals are fully formed and send hormones to the developing brain. At the end of three months, the fetus has all his or her parts and is about 3 inches long. Individual weight varies consierably, but 3 mo, 3 oz., 3 inches is an easy way to remember approximate measurements at this stage.
Early prenatal growth is very rapid, but there is considerable variation from fetus to fetus, especially in body weight.
Advance in brain development – neuron organization, axon development – are critical to attainment of the age of viability. The brain regulates breathing and sucking, which are life-sustaining. < 1 pound, often don’t survive because outside of the womb brain development doesn’t proceed appropriately.Before 22 weeks of gestation a baby will not survive. 50 years ago, it was 23-26 weeks, now 2/3 survive at those ages.
Weight is a good indicator of maturity – at 28 weeks, a typical fetus weighs 3 pounds and has a 95% chance of survival. For genetically small babies or multiples, time since conception is the critical variable. The baby pictured here was born after 26 weeks and 6 days, weighed 8.6 oz. She was a twin and weighed 15 pounds by her first birthday.
Each day in the final three months increased the odds the baby will be healthy, not just survive. Mature neurological, respiratory and cardiac systems are the key. Weight in the last 3 months is about 4.5 pounds. The mother child bond deepens – the baby’s movements increase the mother’s awareness. The baby hears, smells and notices mom’s behavior, being soothed by regular walking and jumping to sudden noises.
Doctors on an Australian military base traced an increase in blindness among newborns to rubella (German measles) contracted by pregnant women a few months earlier.
Realized that some diseases during pregnancy could harm a fetus.
The effort to understand what triggered such damage gave rise to:
Thalidomide, a sedative, in the 1950’s had an impact during weeks 6 or 7 when arms and legs are formed, but no impact after week 9.. Timing determines what areas and how profound of an impact a teratogen has on the developing person. Remember, these are called critical periods. Because the exact timing of conception isn’t always know, drs recommend stopping the use of recreational drugs, certain prescription and update their immunizations if they are trying to conceive or are not taking measures to prevent pregnancy. Prenatal vitamins are a part of this preparation. Folic acid is especially important for neural tube formation – which becomes the nervous system. Most people are deficient in folic acid even though many foods are now supplemented with it.
