Kathleen Stassen Berger

1

Part I

Prenatal Development and Birth

Chapter Four

From Zygote to Newborn

Risk Reduction

Birth

2

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)

3

• 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

4

• 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

5

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

6

• 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

7

• 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

8

• 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

9

• In the fourth, fifth and sixth months:

– heartbeat becomes stronger

– cardiovascular system becomes more active

– brain increases about six times in size

10

• 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.

11

12

Risk Reduction

• teratogens: agents and conditions that can:

– harm the prenatal brain

– impairing the future child’s intellectual and

emotional functioning

13

• 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

14

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

15

Timing of Exposure

16

• 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.

17

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.

18

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.

19

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)

20

• 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

21

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)

22

• For full-term fetus and a healthy mother, birth

can be simple and quick.

23

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

24

Apgar scale: quick assessment of newborn’s condition

including:

– the baby’s color

– heart rate

– reflexes

– muscle tone

– respiratory effort

25

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

26

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.

27

• 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

28

• 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)

29

• 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.

30

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

31

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.

32

• 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

33

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

34

• 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.

35

• 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

36

• 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