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Sex Chromosomes

• XX = Female• XY = Male• XO = Female, Turner’s Syndrome• XXY = Male, Kleinfelter’s Syndrome• XYY = Male, Double Y Syndrome• Fragile X = Male or Female

Berch & Bender (1987); Berger, K. S. (2006); Doyle & Paludi (1998).

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Part I

Prenatal Development and Birth

Chapter Four

From Zygote to Newborn

Risk Reduction

Birth

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From Zygote to Newborn• Prenatal development is divided into three

main periods:– Germinal period (0-2 weeks)– Embryonic period (3-8 weeks)– Fetal period (9 weeks-birth)

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Timing

• Pregnancy begins at conception– Start of gestational age

– Obstetrician may use LMP – 14 days before conception

• Length of pregnancy– 266 days, 38 weeks, or 9 months

– LMP = 40 weeks

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Timing

• Trimesters (3 mo.) vs. germinal, embryonic, and fetal periods

• Due date– Based on LMP

– 5% babies born on that date

– Full term = 3 weeks early or 2 weeks late (preterm and post-term)

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• Germinal period:– First two weeks of prenatal development after

conception– Characterized by rapid cell division and the

beginning of cell differentiation

Germinal: The First 14 Days

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• Embryonic period: – Approximately the third through eighth week after

conception • all body structures, including internal organs,

begin to develop

• Fetal period: – Stage of prenatal development from ninth week

after conception until birth, during which the organs grow in size and mature in functioning

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Germinal: The First 14 Days

• Implantation: – process in which

developing organism burrows into placenta that lines uterus

• Placenta: – organ that surrounds

developing embryo and fetus, sustaining life via the umbilical cord

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• Embryo: a developing human organism from about the third through the eighth week after conception

Embryo: From the Third Through the Eighth Week

4 weeks ¼ in. 5 weeks 7 wks. <1 in. 8 wks. 1 in.

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• The developing organism is called a fetus from the start of the ninth week after conception until birth

Fetus: From the Ninth Week Until Birth

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• At the end of the third month, the fetus has all its body parts

• Weighs approximately 3 ounces and is about 3 inches long

The Third Month

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• In the fourth, fifth and sixth months:– Heartbeat becomes

stronger– Cardiovascular system

becomes more active – Brain increases about six

times in size

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• Age of viability: age at which a fetus can survive outside the mother’s uterus if specialized medical care is available

– About 22 weeks after conception

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Final 3 Months• Brain waves indicate responsiveness• Lungs expand and contract, using the

amniotic fluid as a substitute for air• Heart valves, arteries, and veins circulate the

fetal blood

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Risk Reduction

• Teratogens: agents and conditions that can– Harm the prenatal brain– Impair the future child’s intellectual and emotional

functioning

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• Once it was thought the placenta screened out all harmful substances.

Determining Risk

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– Teratology: science of risk analysis, the study of birth defects

– Risk analysis: to determine likelihood of harm, science of weighing the potential effects of a particular:

– event – substance– experience

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Timing of Exposure

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– Threshold effect: situation in which a certain teratogen is relatively harmless in small doses but harmful once exposure reaches certain level (the threshold)• Vitamin A beneficial in low doses, dangerous

in high doses

– Interaction effect: result of a combination of teratogens• Alcohol, tobacco, and marijuana

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Genetic Vulnerability– Dizygotic twins, exposed to same teratogens

but have only half their genes in common, are born with different abnormalities• Suggests both protective and vulnerable genes

– Cleft lip, cleft palate, club foot more common in some families• Suggests genetic vulnerability

– Neural tube defects

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Protective Measures

• Impact of teratogens cannot be predicted before mid-pregnancy

• Some pregnant women are exposed to the tetragons with no evident harm

• Some defects occur even though the woman avoids all known tetragons while pregnant

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A View From Science

• Alcohol in high doses is a proven teratogen• 40 years ago drinking during pregnancy was

believed to be harmless • Obstetricians noted that some patients who

drank heavily while they were pregnant had babies with distorted faces

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• Fetal alcohol syndrome (FAS): cluster of birth defects – Abnormal facial characteristics – Slow physical growth– Cognitive delays or deficits– Impulsiveness

• Fetal alcohol effects (FAE): condition in which child has been exposed to alcohol before birth– Some signs of fetal alcohol syndrome but does not

meet all the criteria

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Benefits of Prenatal Care

• Tests done during pregnancy can diagnose problems early on, and remedies can be put in place in some instances

• Sonogram: image of unborn fetus (or an internal organ) produced by high-frequency sound waves (ultrasound)

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• For full-term fetus and a healthy mother, birth can be simple and quick

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The Newborn’s First Minutes

• Most newborns begin to breathe as soon as their head emerges.– first breath causes infant’s color to change– eyes open wide – the tiny fingers grab – toes stretch and retract– mucus in the baby’s throat is removed– umbilical cord is cut to detach the placenta– placenta is expelled

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Apgar scale: quick assessment of newborn’s condition including:– the baby’s color – heart rate– reflexes– muscle tone– respiratory effort

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Medical Intervention

• About 31% of births in the U.S. are cesarean section, (also called c-section)

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Birth In Developing Nations

• In the U.S. only 1% of births take place at home.

• Worldwide most births occur at home• Doula- a woman who helps with the birth

process- Also helps with breastfeeding and newborn care

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• Anoxia:– lack of oxygen that can cause brain damage or

death to the baby– means “no oxygen”

• Cerebral palsy: – disorder that results from damage to brain’s motor

centers– People with cerebral palsy have difficulty with

muscle control, so their speech and body movements are impaired.

Anoxia

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• Average weight of a newborn is 7½ lbs.– Low birthweight (LBW): a body weight at

birth of less than 5½ lbs.– Very low birthweight (VLBW): a body

weight at birth of less than 3 lbs, 5oz.– Extremely low birthweight (ELBW): a body

weight at birth of less than 2 lbs, 3 oz.

Low Birthweight (LBW)

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• Preterm birth: occurs 3 or more weeks before full 38 weeks of a typical pregnancy– Preterm babies are typically (but not always)

LBW because they miss final weeks of weight gain

– Small for dates or small for gestational age (SGA)- birth weight is lower than expected given the time of conception

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Social Support

• The developing person is affected by quality of:– medical care – education – culture – social support

• Fathers and other relatives, neighbors, cultures, and, clinics can reduce risk of birth complications

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Mothers, Fathers, and a Good Start

• Birth complications can have a lingering impact on the new family, depending partly on:– sensitivity of hospital care – the home

• To reduce stress on an infant who has to stay in the hospital, parents are encouraged to help with early caregiving.

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• Kangaroo care: form of child care in which the mother of a low-birthweight infant spends at least an hour a day holding the baby between her breast, like a kangaroo

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Help from Fathers

• Fathers can be crucial in the effort to produce a healthy baby.

• Supportive father-to-be helps a mother-to-be:– stay healthy– well nourished– drug-free

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• Parental alliance: cooperation between a mother and a father based on mutual commitment to their children

• Parents agree to support each other in their shared parental roles

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• New mother’s feelings of inadequacy and sadness in days and weeks after giving birth including:– irritability– eating disruptions – sadness– feeling overwhelmed and inadequate

• Affects 10-15% of women

Postpartum Depression

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• Parent-infant bond: strong, loving connection that forms as parents hold, examine, and feed newborn

Bonding