Prenatal DevelopmentPrenatal Development

Chapter 2

Biological Beginnings:ConceptionBiological 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.

The Three Periods of PregnancyThe 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)

Period of the Zygote (Germinal)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

Period of the Zygote (Germinal)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

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)Period of the Zygote (Germinal)

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 conceptionEmbryonic Period – 3rd week after conception

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 conceptionEmbryonic Period – 3rd week after conception

Embryonic Period (2-8 weeks) - OrganogenesisEmbryonic Period (2-8 weeks) - Organogenesis Neural tube develops first, will become

brain and spinal cord Next, heart begins to pump blood

The basic structure of all the organ systems grows

Eyes, ears, nose, jaw, neck, arms legs, fingers & toes form

At the end of this period, it weighs less than one ounce, about one inch long.

– The fetus can kick, bend its arms, form a fist, curl its toes, open its mouth, suck its thumb, smile & swallow

– 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

Period of the Fetus – Growth and Finishing Phase – 3rd MonthPeriod of the Fetus – Growth and Finishing Phase – 3rd Month

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 Period of the Fetus – Growth and Finishing Phase

–Mother can feel movements–Can hear heartbeat with ordinary

stethoscope

–Neurogenesis 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 TrimesterPeriod of the Fetus – Growth and Finishing Phase – 2nd Trimester

–Age at which the fetus can survive outside the mother (38-40 weeks is full term)

–5% survive at 22 weeks

–50% survive at 26 weeks (6 months)

–95% survive at 28 weeks

Period of the Fetus – Growth and Finishing Phase-Age of Viability

Period of the Fetus – Growth and Finishing Phase-Age of Viability

– Depends upon gestational age at birth

– BreathingHyaline membrane disease

– Regulating blood oxygen levels– Apnea– Temperature regulation– Feeding– Parenting – 40% faster weight gain &

brain development with touchKangaroo care

Problems with PreemiesProblems with Preemies

–Begins sleep-wake pattern–Responsiveness, can feel pain

after 24 weeks–React to sounds–Prefer mother’s voice–Adds fat (5 pounds)–Receives antibodies–Assumes birth position (head

down)

Fetal Period – 3rd TrimesterFetal Period – 3rd Trimester

– 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) Teratogens (Monsters)

Examples– Thalidomide – 7000 infants affected

Limbs, heart, ears, kidneys, genitals

– DES (diethylstilbestrol) – reproductive problems in adult children (cancer; abnormalities in reproductive organs)

Teratogens - DrugsTeratogens - Drugs

–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 - DrugsTeratogens - Drugs

–Cocaine–Heroin/methodone

Prematurity, LBW, breathing difficulties, physical defects, infant death, stressed and drug addicted

–MarijuanaSmaller head size, disturbed

sleep, inattention in infancy

Teratogens – Illegal DrugsTeratogens – Illegal Drugs

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 - tobaccoTeratogens - tobacco

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 - AlcoholTeratogens - Alcohol

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 - AlcoholTeratogens - Alcohol

Environmental TeratogensEnvironmental 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

Rubella

HIV/AIDS

Genital herpes

toxoplasmosis

Teratogens – Infectious diseasesTeratogens – Infectious diseases

Nutrition

Emotional stress

Maternal age & previous births

Other Maternal FactorsOther Maternal Factors

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 CarePrenatal Health Care

Approaches to ChildbirthApproaches to Childbirth

How much medical care/availability?

Should it be natural or prepared?

How about the epidural?

How about a midwife (or a doula)?

The Birth ProcessThe 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)

Birth Complications and Medical InterventionsBirth Complications and Medical Interventions–Anoxia–Breech position–Cerebral palsy–Fetal monitors–Medication (90-95% of births)

Analgesics, anesthetics–Cesarean delivery (30% of births)

Low Birthweight Infants (LBW)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

Low Birthweight Infants (LBW)Low Birthweight Infants (LBW)

–Preterm babies – born early (35 or fewer weeks) may be weight appropriate

–Small-for-date babies have more serious problems.

Apgar (1 & 5 minutes after birth)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

The Newborn - ArousalThe Newborn - Arousal

Sleep 18-20 hours per day

50% is REM sleep

SIDS (Sudden Infant Death Syndrome)