Make your own free website on Tripod.com


Fertilization
The Process of Fertilization
Ovulation occurs. Sperm, when present, travel up the fallopian tube and one may fertilize the egg.
The egg changes composition as soon as a sperm penetrates the ovum. When the nuclei of the male and female cells meld together fertilization has occurred, & a zygote is formed.
Genetics
Chromosomes, DNA, and Fertilization
We have 23 pairs of chromosomes
22 are autosomes.

1 pair is the sex chromosomes.

The chromosome pairs are a combination of the two parents - unless the egg was cloned.

We normally get 23 single strands from our mother and another 23 single strands from our father, but this does not always happen.
PRENATAL DEVELOPMENT
Principles of Prenatal Development
Proximodistal
Growth occurs from the middle to the outside.
Cephalocaudal
Growth occurs from head (top) to feet (bottom).
Mass to specific
Large structures appear before the finer details.
Large movements occur before finer ones.

The three prenatal stages of development:
PRENATAL DEVELOPMENT
The Germinal Stage
Day 1 to 14
Not yet attached

PRENATAL DEVELOPMENT
The Embryonic Stage
Week 3 to week 8
Week three the heart beats
At Nine Weeks
PRENATAL DEVELOPMENT
The Fetal Stage
Week 9 to birth


Pregnancy
Gestation period = 267 to 277 days
which is broken into three equal trimesters
There is much variability in the experience of pregnancy, but generally:
First Trimester:
A flood of hormones can produce fainting, headaches, weariness, tender breasts, and morning sickness.
Miscarriages (spontaneous abortions) are more prevalent in this trimester.
1 in 10 pregnancies end in miscarriage.
With women in their late 30’s, this increases to 1 in 5.
Pregnancy
Second Trimester:
Need for maternity clothes
“Quickening” around week 18 as baby begins to kick
Attachment begins in earnest
A strong positive attachment predicts positive maternal bonding after birth.
Third Trimester:
Ever increasing physical and emotional issues
Leg cramps, backaches, anxiety, numbness, heartburn, insomnia
Pregnancy
Emotions and the wider world
The woman’s support group plays a strong role in the experiences of birth.
Will it be a pleasant or unpleasant experience?
Economic factors of the family
The mother’s mental health
Availability of health care
Love & care from those around her (social support)
Fear Factor
Will there be complications or defects?
Pregnancy
Needs of the father
Fathers’ concerns may be overlooked.
Men have fears and worries about their wives’ and babies’ well-being.
Men have worries of their own that they may not be able to voice.
Will the baby take away from my relationship with my wife?
Will I be a good father?
How can I be an involved father and do my job as well?
Threats to the Developing Baby
Teratogens – substances that harm the fetus
Some examples of known teratogens:
Medications – Thalidomide
Diseases – Rubella, AIDS, Toxoplasmosis
Drugs – Alcohol, Cocaine, Meth
Environment - Pesticides, Radiation, Lead, Mercury
Stress
Teratogens
All body parts do not develop at the same time.
Crucial (critical) periods occur for each body part.
In a critical period, it is easier to “derail the train.”
For example, Rubella can affect the baby’s heart or ears, depending on the time during the first trimester when the mother contracted the disease.

Teratogens
Basic principles
Four principles to remember about teratogens:
Teratogens are most apt to cause major structural damage during the embryonic period, the greatest time of organ formation.
Teratogens can effect the developing brain throughout pregnancy.
Teratogens operate in a dose-response relationship, but we do not know where that threshold lies, so it is better to err on the side of caution and stay away from teratogens during pregnancy.
Teratogens may exert their influence long after exposure.
Two Prevalent Teratogens
Smoking
One in nine pregnant women in the US smoke.
Primary danger is reduced birth weight, a major cause of various developmental problems
As few as 6 cigarettes a day
Alcohol
Fetal Alcohol Syndrome – the number one preventable birth defect
Features include low birth weight, abnormally small brain, facial abnormalities, developmental disorders such as mental retardation and seizures
How much is too much?
Measurement issues
What should we do?
Should we take 1000 women and make them drink or smoke during pregnancy? That’s not an ethical experiment!
We have to trust self reports; but will a woman give us the actual number of times she drank during pregnancy? Will she even remember?
Correlational surveys and studies are still being done in this area to try to find out the exact amount that is safe, but it could be years before we know. In the meantime don’t smoke or drink.
Threats from Within
Genetic and Chromosomal Disorders

We are supposed to have 23 chromosomal pairs, but sometimes we get an incorrect number.

Too many or too few chromosomes can occur.
Down syndrome – trisomy 21
Turners syndrome – X
Supermale syndrome XYY
Threats from Within
Mutations on the chromosomes
Humans have about 50,000 genes arranged on 46 chromosomes (23 chromosome pairs).
Genes come in pairs – one on each chromosome- and determine specific traits.
While some traits are dependent on interactions among many chromosomes, other traits are determined by one chromosome.
In the single allele case (single-gene disorder), one gene may be dominant and the other recessive.
If the faulty gene is “sex-linked” it occurs on one of the sex chromosomes. (i.e. Hemophilia)
If the faulty gene is “autosomal” then it comes in pairs. If the faulty trait is recessive, then it requires both alleles to be recessive for the trait to occur - called recessive autosomal disorders. Otherwise, it is a dominant autosomal disorder and only takes one allele to occur.
Threats from Within
Hemophilia is a sex-linked single gene disease carried on the X chromosome.
The “Hollywood Squares” below is the normal method for figuring out how simple “single allele” genetic inheritance works. In the picture below, the normal black “X” in the carrier mother is a normal chromosome with a dominant normal gene, while the green “ X” is the chromosome that carries the recessive gene for hemophilia. The bold black little “x” is a normal chromosome which comes from the father.
Threats from Within
In the previous example, we saw a normal father and a carrier mother and what could happen when their chromosomes combine to create a child. They have a 25% chance of having a normal female child and 25% chance of having a carrier female child. They also have a 25% chance of having a normal male child and a 25% chance of having a male hemophiliac. When added up, they have a 75% chance of having a child with no outward signs of a problem and a 25% chance of having a hemophiliac.

What if the father has the trait and the mother is a carrier?
Genetic and Chromosomal Abnormalities
Supermale syndrome = Xyy
Kleinfelter’s syndrome = XXy
Fragile X = XY, but the X is broken
Turner’s syndrome = X
There is no “only” Y - because the X is absolutely required for development to occur
Parkinson’s disease = C# 4
Usher & Down syndromes= C# 21
Alzheimer’s disease C# 1, 14, 19, and 21.
Cystic Fibrosis = C# 7
Tay-Sachs Disease = C# 15
Phenylkeptonuria = C# 12
Huntington’s Disease = C# 4
Duchenne muscular dystrophy = C# X
Tools of Discovery
Genetic Counseling
People can have their genes tested for specific abnormalities.
If both partners’ genetic codes are known, then a genetic counselor can predict their child’s chances of getting a disease.


Pictures can show gross deformities
Ultrasound technology is commonly used to date the pregnancy and chart the fetus’s growth, but it can also reveal structural abnormalities.

Tools of Discovery
Prenatal tests for genetics:
Amniocentesis
Removal of cells from the amniotic fluid and test the genetic structure.
Risks: miscarriage

Chorionic Villus sampling
Remove villus from the membrane surrounding the fetus and test its genetic structure.
Risks:
5% risk of miscarriage
Chance of limb impairment


Infertility

Infertility is defined as the inability to conceive a child after one year of unprotected intercourse.
Infertility in the U.S. affects 1 in 6 couples.
It’s both a female and a male “problem.”
Infertility can cause grief, despair, a feeling of loss of control, loss of self-esteem, anger, and guilt.

Alternate Means of Conception
Assisted Reproduction Technology Sometimes, when it is difficult to conceive, science can lend a hand.
Alternate Means of Conception
Alternate Means of Conception
Alternate Means of Conception
Alternate Means of Conception
Alternate Means of Conception
BIRTH
Stage 1: Dilation and Effacement
Stage 2: Birth
Stage 3: The Expulsion of the Placenta
Some threats during birth include: baby in breech position, cervix not fully dilating, difficult position of umbilical cord or placenta.
Birth options:
Natural childbirth
Deliver without medication with the help of midwife or doula.
Sometimes, medical intervention is needed.
Cesarean
Used a great deal in some countries
Used in the U.S. if complications occur
THE NEWBORN
Tools of Discovery:
Newborn Tests
The Apgar Scale: tests heart rate, muscle tone, respiration, reflex response, and color.
Threats after Birth
Preterm: born too soon and/or too small
Infant Mortality
Death in the first year of life
Infant Mortality
Greatest threat to newborn – birth weight.
Low birth weight = less than 5.5 lbs.
Very low birth weight = less than 3.25 lbs.

Infant mortality in the U.S.:
7 babies per 1000 (25th vs. other countries)
White: 5.8 per 1000
African-Americans: 13.9 per 1000
Factors: socioeconomic; health practices; unequal access to prenatal care