PSYC 2314Lifespan Development

Chapter 4

Prenatal Development and Birth

Stages of Prenatal Development

• Germinal period– First two weeks– Within hours after conception, the one-cell

zygote travels down the Fallopian tube toward the uterus and begins the process of cell division and growth

Stages of Prenatal Development

• Germinal period– Soon, differentiation occurs, a process first

clearly seen when the multiplying cells separate into two distinct masses, one inside the other. The outer cells will become the placenta; the inner cells form a nucleus that will become the embryo.

– If all goes well, implantation of the cell mass occurs.

Stages of Prenatal Development

• Embryonic period– Begins as the organism begins differentiating

into three layers, each of which will become a key body system.

– A fold in the outer layer of cells becomes the neural tube, which will become the brain and spinal column (the central nervous system).

Stages of Prenatal Development

• Embryonic period– In the fourth week, the cardiovascular system is

functioning; the eyes, ears, nose, mouth start to form.

– At five weeks, the arm and leg buds appear and the embryo is about ¼ inch long.

– By the end of the second month, the developing organism weighs about 1 gram, is 1 inch long, and has all the basic organs (except the sex organs) and features of a human being.

Stages of Prenatal Development

• Fetal period– During the third month, the sex organs begin to

take shape.– During the early weeks of life, the placenta

develops rapidly. This organ connects the circulatory system of the mother with that of her growing embryo, allowing nourishment to flow to the developing organism and transporting wastes away.

Stages of Prenatal Development

• Fetal period– In the mid three months, the systems develop more

fully. The crucial factor in the fetus’s attaining the age of viability, beginning at about 22 weeks, is brain maturation, which is essential to the regulation of the basic body functions of breathing, sucking, and sleeping.

– By 28 weeks, the typical fetus weighs about 1,300 grams (3 lbs.) and has a greater than 90 % chance of survival.

Stages of Prenatal Development

• Fetal period– During the last 3 months, the respiratory and

cardiovascular systems mature dramatically.

– Weight gain during last weeks stores fat, which will provide a layer of insulation when the child is no longer surrounded by the mother’s warmth. The weight gain also provides nourishment and vitamins that will be used until the mother’s breast milk is fully established.

Fetus’s Responses

• Physiological interdependence

• Fetal movements

• Hearing

Teratology

• The scientific study of birth defects

• A science of risk analysis, which attempts to evaluate what factors can make prenatal harm more, or less, likely to occur.

• Teratogens—substances or conditions as viruses, drugs, chemicals, stressors, and environmental hazards.

3 Crucial Factors

• Timing of exposure

• Amount of exposure

• Developing organism’s genetic vulnerability to damage from the substance

Critical periods

• Physical structure and form-embryonic

• For conditions (such as severe malnutrition) and substances (such as heroin), that disrupt and destabilize the overall functioning of the woman’s body, there are two critical periods: the very beginning and the near the end of the pregnancy

Critical periods

• At the very beginning, when stress during the germinal period can impede implantation.

• Near the end, when the fetus most needs to gain weight and when the cortex of the brain is developing, making the fetus particularly vulnerable to damage that can cause learning disabilities.

Critical periods

• Also, instability of the mother’s body systems (chills, shakes, etc.) can loosen the placenta or cause hormonal changes, both of which can precipitate birth.

• For behavioral teratogens there is no safe period. The brain and nervous system can be harmed throughout the prenatal development.

Amount of Exposure

• Threshold effect: the substance is virtually harmless until exposure reaches a certain frequency or dosage.

• Interaction effect: the combination of threshold teratogens taken together may make them more harmful at lower dosage levels than they would be individually.

Genetic Vulnerability

• Susceptibility to alcoholism involves a genetically related defect in a specific enzyme.

• A deficiency in folic acid in the mother’s diet may also result in genetic defects.

• Males not only have a higher rate of teratogenic birth defects and later teratogen-related behavioral problems, but also a higher rate of spontaneous abortions.

Teratogens

• Rubella (German measles)– If contracted early in pregnancy, it can cause

blindness, deafness, heart abnormalities, and brain damage.

• Human Immunodeficiency Virus (HIV)– A pregnant women with HIV may pass the

virus on to her fetus either during pregnancy or childbirth. Infants who have HIV will eventually develop pediatric AIDS.

Teratogens

• Psychoactive Drugs– Slow fetal growth, contribute to premature

labor, and may produce both short- and long-term brain deficits.

Teratogens

• Alcohol Consumption– Large doses of alcohol can trigger the physical,

behavioral, and mental symptoms of fetal alcohol syndrome (FAS).

– Even moderate alcohol consumption during pregnancy (more than ½ ounce of absolute alcohol) can produce the intellectual impairment of fetal alcohol effects (FAE).

Teratogens

• Smoking– Increases the risk of abnormalities and reduces

birthweight and size; babies whose mothers smoked are shorter at birth and in the years to come. They are also more likely to have respiratory problems.

Teratogens

• Drugs– Prenatal exposure to marijuana has been linked

to central nervous system impairment.– Exposure to heroin causes slower fetal growth

and premature labor.– Cocaine use during pregnancy retards fetal

growth, increase the risk of problems with the placenta, and often leads to early learning difficulties.

Protective Measurements

• Complete abstinence from drugs even before pregnancy

• Abstinence after the first month• Moderation throughout pregnancy (if

abstinence is not possible)• Minimizing maternal stress by seeking

social support• Obtain good postnatal care

Birthweight

• Low birthweight (LBW)– Less than 5 ½ lbs.

• Preterm– LBW infants who are born more than 3 weeks

early

• SGA (small for gestational age)– Infants born close to the due date but weighing

less than most full-term newborns.

Poverty and LBW

• Pregnant women at the bottom of the SES are more likely to be ill, malnourished, teenaged, and stressed

• If they are employed, their jobs often require long hours of physically stressful work, exactly the kind that correlates with preterm and SGA

• They often receive late or inadequate prenatal care, breathe polluted air, live in overcrowded conditions, ingest unhealthy substances

Normal Birth

• Begins at about the 266th day after conception, when the fetus’s brain signals the release of hormones that trigger uterine contractions in the mother.

• The first stage of labor (until the baby’s head emerges from the birth canal) usually lasts 6 hours in first births and 3 hours in subsequent births.

Apgar Scale

• Used to assign score between 0 and 2 to the newborn’s heart rate, breathing, muscle tone, color, and reflexes at 1 minute after birth and again at 5 minutes.

• A score of 7 or better indicates the newborn is not in danger; below 7, infant needs help in establishing normal breathing; and below 4, the baby is in critical condition.

Medical Attention/Intervention

• Medical procedures are overused: episiotomies and C-sections

• Routine procedures: IV, fetal monitoring, are rooted in tradition rather than in medical necessity.

Birth Complications

• Birth complications are more likely if the fetus is already at risk because of low weight, preterm birth, genetic abnormality, or teratogenic exposure.

• Researchers now realized that cerebral palsy (difficulties with movement control resulting from brain damage) results from genetic vulnerability, worsened by teratogens and a birthing process that includes anoxia (a temporary lack of oxygen).

Birth Complications

• Many hospitals now provide high-risk infants with regular massage and soothing stimulation.

• When they are brought home, high-risk infants are often more distractible, less obedient, and slower to talk. However, long-term impairment is not inevitable.

Parent-newborn Bond

• Emphasize the tangible as well as the intangible attachment of parent to child in the early moments after birth.

• Diane Eyer-bonding is a social construction that developed as a reaction against the medicalization and depersonalization of traditional hospital births.

• Extensive research has shown that the events right after birth are just one episode in a long-term process of bonding between parent and child.