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Chapter 3: Prenatal Development and Birth

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William Cockrell

on 12 September 2016

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Transcript of Chapter 3: Prenatal Development and Birth

Prenatal Development and Birth
Conception
Conception :
the process by which the zygote is created
Requirements for conception are sperm and an ovum, and a working reproductive system (this is not always the case as we shall see)
Contrary to belief, most pregnancies occur within a three day period, the day of ovulation and the two days before.
A woman has all of her ovums produced at birth; men produce up to 300 million sperms a day.
The process of menstruation is NOT creating ovum's but releasing already created ovums and the lining of the uterus.
The three major periods of prenatal development are : A) the Zygote B) The Embryo and C) The Fetus
There are multiple "safe guards" established in the body to prevent pregnancies (i.e. it is actually very hard to get pregnant)
Development of Zygote
The
germinal period
lasts from conception until around two weeks
Zygotes simply look like a mass of cells.
Zygotes originate in the fallopian tubes and stay there until the second week.
Eventually the zygote has enough cells to form a more complex organism called a
blastocyst.
The blastocyst attaches to the wall of the uterus and starts rapidly forming
anticipatory structures of development
.
The cells inside the blastocyst are called the
embryonic disk
while the cells on the outside are called the
trophoblast
.
Implantation and further development
Implantation :
the term used to describe the process of the blastocyst burrowing in the uterine lining.
After implantation, the blastocyst starts growing at a much faster rate due to sharing blood with the mother.
Amnion
: the first structure that develops which surrounds the infant in
amniotic fluid
Yolk Sac :
initiates the development of red blood cells until the liver, spleen, and bone marrow start producing the cells.
Placenta and Umbilical Cord
The placenta allows nutrients and oxygen to travel from the mother to the zygote. Blood does NOT cross between the zygote and mother.
Umbilical Cord:
the cord that eventually develops to 1-3 feet that delivers nutrients more efficiently to the zygote. The umbilical cord also disposes of waste in the placenta.
The analogy of the umbilical cord and the "tether" to an astronaut are very helpful in understanding it's importance.
Very rarely, the umbilical cord can damage the developing zygote by either not forming properly or strangling the fetus.
The placenta is a protective barrier for the zygote
Embryonic Development
The developmental period for the embryo goes from implantation to the eighth week of pregnancy.
Neural tube :
part of the ectoderm that becomes the spinal cord and brain. This does not develop properly in infants with spina bifida
Fetal Development
Longest period of development that is broken down into three trimesters
By the third month the fetus is physically moving enough for the mother to notice.
The sex of the fetus can be determined by the 12th week of development. If the embryo receives enough testosterone the embryo will become male. No exposure to testosterone results in a female embryo. There are rare occurrences where this does not happen.
The fetal heartbeat can be heard via stethoscope by the third month.
Vernix :
the coating that is visible on newborns. This coating is helpful in the womb because it prevents the skin from chapping due to being in fluid the whole time.
The brain rapidly grows in weight during the second trimester
The Third Trimester
Age of Viability :
the point at which a fetus can survive outside the womb on it's own. There is no set date and it differs for each fetus. The typical range is between 22-26 weeks.
Fetal activity is a believed indicator of psychological adjustment. Fetal infants who were very active in the third trimester handled stress better at age 1 and were less fearful at age 2.
Is it typical for children with disorders to be less active in the womb? Early research appears to support this, but is still far from conclusive.
Fetuses form pain receptors around 23-30 weeks.
Fetuses in the third trimester are dependent on receiving antibodies from their mothers to ward off illness.
The fetus will finally move into the classic "fetal position"
Teratogen:
Any substance or stimuli that is harmful to the development of fetal development. The following factors have been found to influence the damage done by teratogens:
Dose:
the amount of dosage and period of time exposed to the teratogen (e.g., exposure to radiation)
Heredity:
genetic factors determine that some developing fetuses are more resistant to teratogen exposure.
Contributing factors:
the presence of one teratogen or multiple teratogens influences the severity of abnormalities developing. Poor nutrition of the mother, lack of prenatal care, etc can exacerbate the teratogens
Age:
Many teratogens are more harmful in specific periods of development (e.g., one teratogen in the first trimester may cause an automatic miscarriage whereas this might not happen if exposed in the third trimester).
Teratogens Continued
Teratogen exposure influences both physical and psychological traits.
Most of the time the defects are not present at birth and develop much later
Sometimes exposure to teratogens makes the child more susceptible to negative influences
DES was one drug that caused abnormalities for
multiple generations
Accutane was the most common teratogen in America for a long time along with other over the counter medicines.
Knowing you are pregnant ASAP is critical to avoiding teratogen exposures.
4% of pregnant women in America use illegal drugs. The infants are born addicted from exposure in the womb.
Fetal Alcohol Spectrum Disorder
There are three medical diagnoses related to exposure of alcohol in the womb :
Fetal Alcohol Syndrome (FAS) :
stunted development, facial abnormalities, smaller head, and cognitive deficiencies. Wide range of physical abnormalities.
Partial Fetal Alcohol Syndrome (p-FAS) :
less severe form of FAS where the child displays at least two facial abnormalities and brain injury. Typically, the infant is exposed to lower amounts of alcohol than children with FAS.
Paternal alcohol consumption before and after conception are primary causes of p-FAS.
Alcohol-related neurodevelopmental disorder (ARND) :
the child has at least three cognitive/psychological developmental abnormalities. Physical development is NOT effected.
Environmental Teratogens
Radiation causes devastating effects on any human life. Many fetuses/embryos exposed to radiation die almost immediately (if the dose is large enough).
After the Atomic bombs in Hiroshima and Nagasaki as well as the Chernobyl explosion, many children born of victims had drastic physical and mental abnormalities.
http://atomicbombmuseum.org/3_health.shtml
Most pregnant women know to avoid mercury and lead exposure
Environmental pollutants are becoming more of a concern due to our dependency on fossil fuels and lack of proper waste management.
More minor symptoms are caused by exposure to X-rays
Dioxins :
toxic chemicals that are created due to anything being burned (e.g., burning trash, trees, cigarette ash, etc.). These chemicals cause brain and immune system problems in infants. They increase breast and uterine cancers in women.
Men who have higher rates of dioxins are more likely to father girls than boys. Therefore it is believed that dioxins are GERMLINE mutations (influences the sex chromosomes)
Infectious Diseases and Development
Rubella/Measles : half of pregnant women who have measles during pregnancy often deliver infants with various deformities.
Less common in developed countries due to routine vaccinations; developing countries often still have many infants effected by this.
1/4 of all pregnant women in South Africa are HIV+
95% of all new HIV infections occur in developing countries.
The chance of a pregnant mother passing HIV to her infant is around 20-30%.
HIV progresses to AIDS for infants much faster than adults taking medicine. Children born with HIV typically do not live to their 1st birthday.
One drug, Zidovudine (ZDV) reduces HIV transmission between mother and infant to less than 5%. This drug is typically NOT available in countries that are devastated by HIV the most (developing countries).
Herpes is less treatable if the child is infected during pregnancy. A caesarean is required if the child is not infected by the mother's labor to prevent the disease.
Maternal Factors and Development
Exercise is helpful but the type matters! Regular, moderate exercise causes increase birth weight (this is good). Mothers who exercise a lot and it is high-intensity often deliver babies with lower birth weights.
Pregnant women should always consult their OGBYN about appropriate exercise activities.
The fad of trying to not gain weight during pregnancy is HARMFUL TO THE INFANT!!! A women should gain 25-30 pounds during pregnancy.
Proper nutrition is directly correlated with appropriate brain development. The development of the brain suffers most with malnutrition.
Immune systems are lower in children that developed with a malnourished mother.
Children also develop psychological problems.
All pregnant women should take folic acid to prevent spina bifida, anencephaly, and reduce the chances of premature delivery.
A stressed pregnant mother can cause development problems in the fetus.
Being older usually causes biological problems, being too young causes social problems.
Labor and Delivery
Apgar Scale :
the scale used to assess the neonate's physical condition at 1 minute and 5 minutes after birth.
Natural Childbirth
Natural Childbirth :
the process by which mothers try to reduce pain naturally, avoid medical interventions, and try to focus on the "miracle" of giving life.
Fear of labor causes many women to tense their muscles and this causes the pain to intensify during contractions.
The three factors suggested by Read & Lamaze are: educational classes, relaxation and breathing techniques, and a labor coach.
Studies have shown that women who have social support during labor have easier experiences than women who are alone during labor.
There is a believed link between social support and a reduced chance of needing a cesarean.
Finally, children born of mothers who have social support typically score higher on the APGAR scale.
The 9 Months That Made You
http://iis.bhsu.edu:2213/PortalPlaylists.aspx?aid=27675&xtid=48258
http://digital.films.com/PortalPlaylists.aspx?aid=27675&xtid=40894&loid=67272
http://digital.films.com/PortalPlaylists.aspx?aid=27675&xtid=40894&loid=67265
Symbolic Meaning of Pregnancy
"Is interpreted in feminist writings as a biological process that has been subject to ideological constructs" (Hunt, pg. 58, 2005).
Cultural norms are placed in many cultures where pregnancy is viewed as a "handicap" and limits a woman's social participation.
Most social controls over acceptable pregnant behavior is influenced by patriarchal beliefs.
The textbook uses the example of menstruation being a taboo.
The "taboo" is socially constructed by men to keep dominance over women (Douglas, 1966).
It also reinforces the separation of gendered work spheres
Symbolically illustrates women as "unclean" and men as "pure"
Bengali rituals after pregnancy/American "churching"
Medicalization of Motherhood
Medical Nemesis
- How is medical technology harmful to mankind?
Extreme Plastic Surgeries
Forced Sterilization
Circumcision
Unsafe Abortions (lack of access to safe abortions)
Hormone Replacement Therapy
Remember, the medical field is dominated by men
Feminist researchers argue that men have used medical "research" to control women's reproductive choices.
1% of women in America have at home births
Are American women passive "bystanders" in their pregnancies?
A woman will not notice she is pregnant the first two weeks.
Stem Cells:
the zygote is made up of stem cells. These are the first cells that are very different than other cells. Stem cells can create ANY type of cell instead of just the type they are (e.g., blood cells creating other blood cells).
Differentiation:
By the 8th week, stem cells will be replaced with regular cells. Different cells will now develop with different timelines. They also now have specific, localized functions.
60% of zygotes are not going to progress past this stage of development.
The period of the zygote is also sometimes called the "Germinal Period"
Urine and blood tests will NOT detect a pregnancy until implantation occurs (around week 2).
After implantation, it is very important that the mother and embryo's blood DO NOT TOUCH. This can cause septicemia in the mother.
Only 31% of zygotes will become living newborn babies outside of the womb.
Chorion :
the trophoblast creates this membrane to surround the amnion. The chorion eventually develops into the placenta.
Placenta:
the last structure to develop in the germinal period. This is the protective barrier in the womb.
Primitive Streak:
the presence of this feature marks the start of the embryonic stage. The primitive streak is a thin line down the middle of the cellular mass. It will eventually develop into the neural tube.
When we look at overall structures, the head is going to develop around the fourth week.
The blood vessel that will become our heart is first visible around 5-8 weeks. It is not pumping blood at the point, but still developing.
The arms and legs will start to form and separate around the fifth week of embryonic development.
The last step in limb development is that the toes and fingers separate and are no longer webbed (this does not always happen!)
By the end of the embryonic development, the embryo is going to weigh around 1 gram and will be about an inch long.
87% of hospital births in the United States are free of complications
The World Health Organization estimates that 10-15% of births require a
cesarean
(the fetus is removed from the mother's abdomen via a surgical incision).
Countries that have low rates of cesareans have high death rates in childbirth!
Women who have a C-section are less likely to breast feed.
Children who are delivered by C-section are more likely to be obese (16% compared to the 8% of vaginal births). This may actually be related to breast feeding. We will discuss this later.
Does a mother's instinct exist?
Wouldn't this mean all mom's would know how to be an ideal parent (i.e. only a small number of failures)? Remember, an instinct/reflex is a biological response that is present in the majority of the population.
Mothers are flooded with neuropeptides such as oxytocin which initiates contractions and increases strong feelings of attachment when exposed to the newborn.
Most of the 1900s and today, self-help books for expectant mothers continue to be purchased at high rates. This contradicts a natural inclination motherhood.
Motherhood
Postpartum Depression (PPD):
the experience of a new caregiver feeling sad, anxious, angry, and overwhelmed about caring for a newborn. Research is not conclusive on the cause, but it is believed to be chemically influenced by hormones.
Fathers CAN be diagnosed with PPD. This leads us to believe it is not directly linked to the physical birthing procedure. Around 10% of fathers are diagnosed.
Preventing Pregnancies
Unintended Pregnancy:
A pregnancy that was not planned or one that is not wanted.
"Among unmarried women ages 20 to 29, almost 80% of the pregnancies are unintended."
(Benokraitis, pg. 310, 2015).
In the United States, 40% of African-American women have had two or more unintended pregnancies.
Fathers of unintended pregnancies tend to react the harshest and most negatively. It is not terribly uncommon for the stress to cause the father to terminate the relationship with the expecting mother. Men receive little social punishment for this behavior.
In other words, research demonstrates that an unintended pregnancy causes a high risk of dissolving a romantic relationship between an unmarried heterosexual couple.
"About 67% of unintended births are publicly funded, and the proportion is 80% in some states. In low-income families, unintended pregnancies cost U.S. taxpayers about $11 billion a year just for the medical services to women and first-year infant care-money that could be used to finance pre-school programs in poor neighborhoods" (Monea & Thomas, 2011; Sonfield et al., 2011; in Benokraitis, pg. 310, 2015).
Abortion in the United States
Abortion :
the intentional termination of a pregnancy.
The CDC reports that around 1.2 million abortions are performed a year in America.
Unmarried women in their twenties make up 85% of women who have abortions in America.
African-American women have higher rates of abortion than Caucasian women (there is institutional discrimination here!!)
Roe v. Wade :
created in 1973, which made abortion legal again in America.
By the age of 45, 33% of women in the world will have at least one abortion.
2% of all American women have an abortion. This should help you see this is a GLOBAL issue.
60% of women who have an abortion already have at least one child.
69% of women who have an abortion in the United States are below the poverty line.
88% of all abortions in the United States are in the first 12 weeks of pregnancy. Therefore, always discussing late term abortions is a scare-tactic.
73% of women who have abortions report being religious
Two main reasons women in America have abortions is unemployment or no health insurance.
There is more misinformation than truth about abortion in the United States.
Additional Abortion Regulations
Hyde Amendment :
Women cannot use medicaid or most health insurances for an abortion. The only exception is when their life is in danger.
The common cultural opinion is that most women would prefer to die before aborting a child that will take her life.
Most people believe that late term abortions are illegal, but for the most part many doctors are just unwilling to perform them.
All abortion clinics are required by law to have at least one licensed gynecologist.
Women have a higher chance dying driving a car, playing football, driving a motorcycle, or getting a penicillin shot than dying from a legally safe abortion in the first 12 weeks (Deprez, 2013).
.03% of patients that have abortions are required to be hospitalized.
The Center for Medical Progress (VERY misleading name) argues that women who have abortions are at higher risk of breast cancer, infertility, substance abuse, and suicide. Scientific research does NOT support any of these claims.
Since 1994, researchers believe that abortion has dropped by 43% because of the availability of emergency contraception.
Emergency Contraception:
abortion in the first 9 weeks of no menstrual cycle. No surgical procedure is required, the patients typically take RU-486, also known as mifepristone. This is NOT the morning after pill.
Child Free By Choice
Temporary Childless:
Have not had children yet, but want them.
Involuntarily Childless:
These people cannot have children, but may actually want them.
Should couples who are medically diagnosed as infertile have to pay such a high adoption fee?
Voluntarily Childless:
Couples who do not want to have children.
Child Free:
Couples who do not want children often prefer this term.
Childless couples
tends to make people think something is missing.
Women who have never married, are not living with somebody, have at least a bachelor's degree, and grew up with both parents are the most common women to not have children.
As medical technology improves, parents are more cautious in having children if they could pass on hereditary diseases.
Women's experiences of not having children depends on which type of category they classify as.
Voluntarily childless women may grow to have negative feelings about mothers whereas Involuntarily childless women may be resentful against women who choose not to have children.
Gestation:
the time an organism spends developing in the womb. For humans, it is around 166 days (38 weeks).
The Life of A Sperm
Men produce millions of sperm everyday. Each ejaculation results in around 350-500 million sperm.
Semen:
the coating around sperm that prevents sperm from decaying in the vaginal cavity. If sperm is not coated in semen it usually evaporates.
It takes about 6 hours for sperm to reach the ovum. Of the 500 million sperm, only around 300 will reach the ovum.
Sperm are guided by the ovum which is releasing hormones and has a much higher temperature than the rest of the fallopian tubes. The sperm are drawn to the temperature and when they "detect" the hormones they start swimming much faster.
Sometimes partially developed sperm literally push stronger sperm toward the ovum. Some scientists say this is conscious, others say it's coincidence.
When the ovum is penetrated by a sperm, all other attempts at penetrating the ovum will be unsuccessful. Scientists notice the ovum releases hormones immediately after penetration and assume this "hardens" the ovum.
This supports why scientists who perform artificial insemination only have "one chance" to actually implant the ovum with sperm.
If frozen, a man's sperm will last about 12 years. Is it ethical to use the sperm of a man that has passed away?
Cleavage:
the process of zygotes dividing into multiple cells. This first happens 30 hours after conception. The single cell will "cleave" into separate cells.
The Importance of Stem Cells
Let's imagine a person has Parkinson's and their brain is no longer producing the necessary brain cells to function. Research shows inserting stem cells into the brain will cause these cells to act like brain cells OR repair damage.
Embryonic Stem Cells:
the stem cells that are the original cells for all of human development. They need this ability to adapt to organs because we do not have specialized cells yet.
When scientists remove embryonic stem cells from a developing zygote it will be terminated. If embryonic stem cells are not used in the first 15 days, it is too late.
When the media says that doctors remove stem cells from aborted 3 month old fetuses, they are incorrect!
Somatic Nuclear Transfer:
Technological process where doctors clone skin cells in a petri dish. They then insert the cloned skin cells into an ovum. The DNA is identical to the patient so they respond to the stem cells better. This is viewed as more humane, BUT the argument is we are creating artificial life just to use it.
Adult Stem Cells:
Scientists do not know how they are created. They appear when the an organ has experienced massive damage or injury. They try to repair the organ. Scientists do not know how to harvest them. They would be highly beneficial.
Umbilical Cord Stem Cells:
the weakest but easiest to recover. No harm is done to the infant. Parents can now store the umbilical cord stem cells in hopes these cells could help if the child has some form of cancer.
We notice that embryos start displaying Rapid Eye Movement around 21 weeks of development. This demonstrates that embryos DO dream in the womb.
We also notice the fetus will start to suck their thumb around the third month.
If the fetus has severe chromosomal abnormalities, they usually do not survive past the first trimester (3rd month).
One of the easiest ways to determine the fetal period has begun is that bone does not develop until the fetal period.
One out of eight births in the United States is premature (CDC, 2014).
22 week old premature infants rarely survive. Their lungs and heart have not fully formed. The less the lungs have developed, the less likely the infant will survive.
Neonatal Surgery:
most commonly performed during the 3rd trimester. Avoided at all costs unless absolutely necessary. The anesthesia for the mother is often fatal to the developing fetus.
Teratology
Women who plan to have a child are better able to avoid teratogens. A teenager who smokes the first 3 months of pregnancy before finding out is at high risk of teratogen damange.
Teratogen exposure during the embryonic period causes the most physical abnormalities whereas teratogen exposure after then impacts brain and psychological development more.
Sleeper Effects:
damage caused by teratogens that do not appear until much later in life. Examples include: ADD, ADHD, infertility, and cervical cancer.
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