Lecture 3 - Prenatal Development and Birth

General Dynamics of conception

ovulation - approx. every 28 days

The ovum survives 24 hours

sperm survives 5 to 6 days

brief window

Fertilization = union of sperm and ovum; genetic materials fuses

Zygote - period of the zygote (germinal period)

fertilized egg

duration = 2 weeks

• from fertilization to implantation

Blastocyst

hollow, fluid filled ball of cell

• 60-70 of them

• happens on the 4th day

Embryonic disk

cells on inside of blastocyst- become new organism

Trophoblast

The outer ring of cells around the blastocyst will develop into the 3 life support systems

Amnion

protective covering —> encloses organism in amniotic fluid

• functions in cushion + temp. regulation

Placenta

disc-shaped mass of tissue —> partial filter - permits food and O2 to reach an organ and waste products to be carried away

Umbilical cord

rope of tissue that connects placenta to developing organisms

• the anchor

The period of the zygote (germinal period) ends with what?

ends with implantation

implantation 7 to 9 days after fertilization when the blastocyst burrows into the wall or lining of the uterus

the implantation process signals hormonal changes that signal the beginning of pregnancy (often when people can detect pregnancy with home urine tests)

Period of the Embyro (2-8 weeks)

rapid change and development - most rapid prenatal changes: groundwork for all body structures and internal organs is begun

What are the three layers called that the embryonic disk forms into?

Ectoderm- outermost layer, eventually becomes the NS and the skin

Mesoderm- middle later eventually becomes muscle, skeleton, and circulatory system

Endoderm- innermost layer, eventually becomes digestive system, lungs, and glands

Neural tube

becomes the primitive spinal cord and brain that develops early on

when ectoderm folds over

Developments during weeks 4-8

rapid development of baby parts and systems

• internal organs become more distinct

• 3 life support systems mature and develop rapidly

Miscarriages

Spontaneous abortions that happen because of inadequate development (pregnancy ends before the developing organism is mature enough survive outside the womb)

• the embryo separates from the walls of the uterus and is expelled from the uterus

• Some are caused by chromosomal abnormalities

• about 15-20% of recognized pregnancies end in abortion (most occur in first 2-3 months); 90% occur by 12 to 13 weeks

Period of the Fetus (9th week to birth)

“growth and finishing phase”

• developing organs rapidly increase in size

Development is discussed in trimesters = 3 equal time periods in the 9-month prenatal period

Progress at the end of the first trimester (3rd Month)

The physical structure becomes more complete

organs, muscles, and NS organize and connect

behavioral changes like kicking, sucking a thumb, or holding a fist occur

external genitals well-formed by 12th week

fetal heartbeat audible w/ stethoscope

Second trimester (13-24 weeks)

Fetal growth → mother can feel movements

• nearly all brain’s neurons produced by trimester end

Vernix and lanugo form

Vernix

white, cheese-like substance covers fetus and protects skin form becoming chapped

Lanugo

white, downy hair that covers the fetus - helps vernix stick to skin

Third Trimester (25-28 weeks) - Age of Viability

Age of viability (22 to 26 weeks) = age at which fetus can 1st survive if born early (50/50 chance after about 24 weeks)

• half fetuses born around 24 have lots of defects, it is just the way that it happens

Body systems become more complete and prepare for the outside world in the Third Trimester

What happens when the prenatal fetus’s body systems become more complete and are ready for the outside world?

• The brain matures extensively

• Cerebral cortex enlarges

• behavior of the fetus becomes more organized (e.g., sleep patterns)

• fetus responds more clearly to sounds in the external environment

• 8th month: layer of fat develops under skin

• preparations for delivery, change position, lose coating

General Risk Factors for Prenatal babies caused by Environmental Influences

Maternal nutrition

Emotional stress

Material Age

Maternal nutrition

Malnutrition can damage the CNS, leading to fewer brain cells and decreased brain weight

• lower birth weight is linked to adult disease (diabetes, strokes)

  • it is recommended to gain 25-30 pounds and take multivitamins so this doesn’t happen

Emotional Stress

associated with miscarriages, lower birth rate, and premature birth

• less oxygen and nutrients to feed

• stress hormones - higher fetal HR + can heighten stress reactivity for later in life

major life events

chronic stress

Maternal Age

maternal age and prenatal babies have a complex relationship

Women who are in their 20s and 30s have a greater success rate for having healthy babies

After 40, there is a higher risk for infertility, miscarriages, chromosomal defects (e.g., Down syndrome)

• the same can be sad for adolescent moms (low birth rate and prematurity)

Teratogens

Teratogens are another prenatal environmental influence on prenatal babies that are any environmental agent that causes damage during the prenatal period

cause 5-8% of birth defects in live births

Impact of teratogens varies based on what factors?

• Dose-level and degree of exposure

• Genetic predisposition

• Presence of other factors

• Time of exposure

  • sensitive period- parts undergoing rapid development are especially vulnerable

Sensitive period

parts undergoing rapid development are especially vulnerable

What helps keep you and your baby healthy?

• good health and fitness

• balanced diet

• ‘gaining 25-30 lbs

• 5 or more prenatal doctor visits

Common effect of Teratogens on Prenatal babies

• lower birth weight

• prematurity

• miscarriage

• underdeveloped brain

7 Common Teratogens

1. Illegal Drugs

2. Tobacco/nicotine → causes a low birth weight

3. Alcohol → all types matter, alcohol has many negative effects on newborns

4. Prescription and nonprescription medication

5. Radiation

6. Environmental Pollution

7. Infectious disease (e.g, German Measles, HIV/AIDS) → you can transmit the disease to your baby

Do paternal factors matter?

Yes

• exposure to certain amounts can lead to abnormal sperm, leading to birth defects and lower birth weight

• Later paternal age is associated with some birth defects and with autism

Study done about Paternal (dad) Factors

looked at the offspring of men who were older than 40

The offspring were 5.75 times more likely to have autism compared with the offspring of men under 30 years old

• looked at maternal and paternal age. Paternal age (dad) was more related to autism

What was traditional (past) delivery like?

home delivery, natural family eventW

What is current delivery like?

hospitals, medical event

What are some concerns about the medicalization of childbirth

are we treating a natural process like a disease when it doesn’t have to be treated like that?

Some procedures like episiotomies, happen quite often

fetal monitoring inhibits the mother’s mobility, mothers lose the benefit of gravity (gravity helps push everything down and makes childbirth easier)

pain medication, used in more than 80% of births in the U.S.

episiotomies

surgical cuts to the perineum to enlarge the opening

• was done routinely for a while, but there is a debate if it is needed for everyone

• it prolongs the healing process

Pain medication used during child birth

Controversial during childbirth

used in more than 80% of all births in the U.S.

Analgesics - relaxes the mom and relieve pain (e.g., Demerol), cross the placental barrier because it takes over the mother’s entire body, meaning the baby may also be sedated and have no emotion or movement when born

Regional anesthetics- e.g., epidural - relieve sensations in certain parts of the body (60% of women have them) may prolong labor and cause trouble when pushing

Regional anesthetics

e.g., epidural - relieve sensations in certain parts of the body (60% of women have them) may prolong labor and cause trouble when pushing

analgesics

relaxes the mom and relieve pain (e.g., Demerol), cross the placental barrier because it takes over the mother’s entire body, meaning the baby may also be sedated and have no emotion or movement when born

Cesarean Section (C-section)

nature - surgical procedure, baby is removed through the mother's abdominal wall

typically w/ regional anesthesia, the mother is awake

Why are C-sections needed?

infant distress, medical emergency, breech positions (toes are first, not head), failure to progress

Prevalence of C-sections

5.5% of births in 1970, 33% of births in 2015- the most common form of major surgery

4 reasons why a high rate of C-sections is a problem

1. it is a major surgery: there is a longer recovery period

2. It is expensive: possible financial strain for the patient

3. Could signify a spiral of medicalization

4. Mother’s psychological reaction can be quite negative (higher rates of postpartum depression)

Natural or Prepared childbirth - goals and benefits

goals is to make childbirth as comfortable and rewarding for the mother as possible

Typical components: classes, relaxation, coach

Report: moms report feeling more in control, labor is shorter and less stressful for the mom and infant

Natural or Prepared Childbirth- Use of Doula

trained to provide continuous physical and emotional support to the mother

shortens the labor and reduces the need for medication

report- mothers report more positive feelings about the birth processing and less postpartum depression

Natural or Prepared Childbirth - Birthing Centers

Combine the intimacy of home birth with the medical technology of a hospital

They use childbirth as a non-pathological event and only bring in medical equipment when needed

• designed to accommodate the entire process

• delivery typically performed by a licensed midwife

• Encourage preparation (e.g., classes or a plan). Focus on family and control

Fetal Alcohol Spectrum Disorder

a range of physical, mental, and behavioral outcomes caused by prenatal alcohol exposure, including FAS and p-FAS, and alcohol-related neurodevelopment disorder

occurs when mother's drink during pregnancy

3 Stages of Childbirth

1. Dilation and effacement of the cervix (opening of the cervix): the strongest stage of labor, lasting an average of 12 to 14 hours. Over time, contractions of the uterus become more frequent and powerful, causing the cervix, or uterine to open, widen, and thin to nothing; this forms a clear channel from the uterus into the brain canal, or vagina

2. Birth of the baby: lasts around 25-50 minutes, depending on the birth. Strong contractions continue, but the mother also feels the natural urge to squeeze and push with her abdominal muscles. As she does so with each contraction, she forces the baby out

3. Delivery of the placenta: labor comes to an end with a few final contractions and pushes. These cause the placenta to separate from the wall of the uterus and be delivered in about 5 to 10 minutes

Consequences for and caring of pre-term infants

Because the child is very fragile, mothers and fathers are afraid of caring for them because they don’t want to break them. Because of this, the child gets less stimulation, leading to decreased brain development

Pre-term babies are more at risk for child abuse b/c parents get annoyed that they can’t respond to their child

Pre-term infants are especially susceptible to the effects of parenting quality- single poverty mother have a pre-term baby, the baby is less likely to catch up in development because of the quality of parent

Kangaroo care

skin-to-skin contact with the baby and caregiver

Fosters improved oxygenation of the baby’s body, temperature regulation, sleep, breastfeeding, alertness, and infant survival; provides baby with gentle stimulation of the 5 sense