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Kathleen Stassen Berger

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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• 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:– name for a developing human organism from about

the third through the eighth week after conception

Embryo: From the Third Through the Eighth Week

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

• during the fetal period the fetus develops from tiny, sexless creature to a 7 1/2-pound, 20-inch boy or girl

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.

• Early prenatal growth is very rapid, but there is considerable variation from fetus to fetus, especially in body weight.

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

• In the final three months of prenatal life:– 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– impairing the future child’s intellectual and

emotional functioning

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• Once it was thought the placenta screened out all harmful substances.– Doctors on an Australian military base traced an

increase in blindness among newborns to rubella (German measles) contracted by pregnant women a few months earlier.

– Realized that some diseases during pregnancy could harm a fetus.

Determining Risk

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The effort to understand what triggered such damage gave rise to:– 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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• Second important factor is the dose and/or frequency of exposure.– threshold effect: situation in which a certain

teratogen is relatively harmless in small doses but harmful once exposure reaches certain level (the threshold)

– interaction effect: result of a combination of teratogens• Sometimes risk is greatly magnified when embryo or

fetus is exposed to more than one teratogen at the same time.

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Genetic Vulnerability

• Several lines of evidence suggest that genes may be crucial. – 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.

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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 thought 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.– fetal alcohol syndrome (FAS) – fetal alcohol effects (FAE)

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• fetal alcohol syndrome (FAS): cluster of birth defects, including: – abnormal facial characteristics – slow physical growth– retarded mental development

• fetal alcohol effects (FAE): condition in which child has been exposed to alcohol before birth– has 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)– incision through mother’s abdomen and uterus

to allow fetus to be removed quickly, instead of being delivered through the vagina

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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

• cross-fostering: newborns are removed from their biological mothers in first days of life and raised by another female or even male

Bonding