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Discovering the Life Span

Fourth Edition

Chapter 2

The Start of Life

Module 2.2

Prenatal Growth and Change

Section in Module 2.2

The Prenatal Period

Learning Objectives

2.7: Explain the process of fertilization and the three stages of development.

2.8: Describe some of the physical and ethical challenges that relate to pregnancy.

2.9: Describe the threats to the fetal environment and what can be done about them.

The Prenatal Period

Module 2.2 Prenatal Growth and Change

The Moment of Conception and the Onset of Development (1 of 3)

LO 2.7 Explain the process of fertilization and the three stages of development.

Fertilization occurs when the sperm and ovum join to form a new cell.

The Germinal Stage: Fertilization to 2 Weeks

Cell division

Baby is a zygote

Cells form protective layer

Placenta provides nourishment and oxygen

Figure 2-9: Anatomy of the Female Reproductive Organs

The basic anatomy of the female reproductive organs is illustrated in this cutaway view.

Source: Based on Moore & Persaud, 2003.

The Moment of Conception and the Onset of Development (2 of 3)

LO 2.7 Explain the process of fertilization and the three stages of development.

The Embryonic Stage: 2 to 8 Weeks

Baby called an embryo

Baby composed of three layers:

Ectoderm: Outer layer, forms skin, hair, teeth, sense organs, brain, and spinal cord

Endoderm: Inner layer, produces digestive system, liver, pancreas, and respiratory system

Mesoderm: Middle layer, forms muscles, bones, blood, and circulatory system

Brain undergoes rapid growth

The Moment of Conception and the Onset of Development (3 of 3)

LO 2.7 Explain the process of fertilization and the three stages of development.

The Fetal Stage: 8 weeks to Birth

Baby called a fetus

Dramatic increase in size and weight

Organs become differentiated and operational

Brain becomes increasingly sophisticated

Hemispheres grow rapidly

Neurons become coated with myelin

By 3 months, fetus swallows and urinates; by 4 months, mother can feel movement

In weeks 8 to 24, hormones begin the differentiation that results in male or female fetus

Embryo and Fetus

(a) Embryo at 5-6 weeks. (b) Fetus at 8 weeks. (c) Fetus at 14 weeks.

Figure 2-10: Body Proportions

During the fetal period, the proportions of the body change dramatically. At 2 months, the head represents about half the fetus, but by the time of birth, it is one-quarter of its total size.

Pregnancy Problems (1 of 4)

LO 2.8 Describe some of the physical and ethical challenges that relate to pregnancy.

Infertility

Inability to conceive after trying 12 to 18 months

About 15 percent of couples will have problems

Causes

Age of parents

Previous use of birth control, illicit drugs, or cigarettes

Men who have low sperm count

Woman’s mother taking certain drugs during pregnancy

Most common cause: Failure to ovulate

Figure 2-11: Older Women and Risks of Pregnancy

Not only does the rate of infertility increase as women get older, but the risk of chromosomal abnormality also increases.

Source: Reproductive Medicine Associates of New Jersey, 2002.

Pregnancy Problems (2 of 4)

LO 2.8 Describe some of the physical and ethical challenges that relate to pregnancy.

Infertility

Treatments

Artificial insemination

Intracervical insemination (ICI)

Intrauterine insemination (IUI)

In vitro fertilization (IVF)

Intrafallopian transfer (GIFT)

Zygote intrafallopian transfer (ZIFT)

Sometimes a surrogate mother used

Pregnancy rates as high as 48 percent; live births lower

Ethical considerations

ARTIFICIAL INSEMINATION is a process of fertilization in which a man’s sperm is placed directly into a woman’s vagina by a physician. The most common type is intracervical insemination.

IN VITRO FERTILIZATION (IVF) is a procedure in which a woman’s ova are removed from her ovaries, and a man’s sperm are used to fertilize the ova in a laboratory.

Gamete intrafallopian transfer (GIFT) and Zygote intrafallopian transfer (ZIFT) are procedures in which an egg and sperm or fertilized egg are implanted in a woman’s fallopian tubes.

IVF is becoming more successful, with pregnancy rates as high as 48 percent for women under age 35.

Actual live births are less than pregnancy rates because not all pregnancies ultimately result in birth.

Surrogate mother is a woman who agrees to carry the child to term; may be used in cases where the mother is unable to conceive.

Ethical issues include the use of surrogate mothers, in vitro fertilization, and sex selection techniques

Pregnancy Problems (3 of 4)

LO 2.8 Describe some of the physical and ethical challenges that relate to pregnancy.

Miscarriage and Abortion

Miscarriage is spontaneous abortion

Pregnancy ends before child is viable

15 to 20 percent of pregnancies end in miscarriage

Many times mother not aware of pregnancy

Usually due to genetic abnormality

Women who suffer miscarriages experience anxiety, depression, and grief

Depression rates for women who have had a miscarriage remain high

Pregnancy Problems (4 of 4)

LO 2.8 Describe some of the physical and ethical challenges that relate to pregnancy.

Miscarriage and Abortion

Abortion is voluntary termination of pregnancy

About one in five pregnancies end in abortion worldwide

Decision to abort is difficult

Physical, psychological, legal and ethical issues may arise

The Prenatal Environment: Threats to Development (1 of 5)

LO 2.9 Describe the threats to the fetal environment and what can be done about them.

Teratogen: Environmental agent such as virus or chemical that produces a birth defect

Impact of teratogens depend on when they occur

Different organ systems are vulnerable at different times

Mother’s Diet

Important in supporting development of fetus

High-nutrient diet leads to fewer complications

Diet is immense concern worldwide

Figure 2-12: Teratogen Sensitivity

Depending on their state of development, some parts of the body vary in their sensitivity to teratogens.

Source: Moore, 1974.

The Prenatal Environment: Threats to Development (2 of 5)

LO 2.9 Describe the threats to the fetal environment and what can be done about them.

Mother’s Age

Mothers over 30 have greater risk of complications:

Premature birth

Low birth weight

Down syndrome

Infant mortality

Mother’s Health

Illness can cause devastating consequences:

Rubella

Chicken pox

Syphilis and gonorrhea

AIDS

Mental health

Rubella (German measles) prior to the 11th week can cause blindness, deafness, heart defects, or brain damage.

Chicken pox and mumps may cause birth defects and miscarriage, respectively.

Syphilis and gonorrhea can be transmitted to the child.

Babies born with AIDS (acquired immune deficiency syndrome) can have birth abnormalities including small, misshapen faces, protruding lips, and brain deterioration.

A mother’s mental health can affect her children. For example, if the mother suffers from clinical depression while she is pregnant, the development of her children might be negatively affected.

The Prenatal Environment: Threats to Development (3 of 5)

LO 2.9 Describe the threats to the fetal environment and what can be done about them.

Mother’s Drug Use

Legal and illegal drugs pose risk

Legal drugs

Aspirin can lead to fatal bleeding

DES later caused cervical and vaginal cancer in daughters

Illegal drugs

Marijuana restricts oxygen

Cocaine restricts oxygen and blood flow

Babies are born addicted

Babies shorter and weigh less

Babies have serious respiratory problems and birth defects

Often they are impossible to soothe

The Prenatal Environment: Threats to Development (4 of 5)

LO 2.9 Describe the threats to the fetal environment and what can be done about them.

Mother’s Use of Alcohol and Tobacco

Small amounts can impact fetus

Alcohol

Fetal alcohol spectrum disorder (FASD)

Fetal alcohol effects (FAE)

Two drinks a day has been associated with lower intelligence

Tobacco Use

Reduces oxygen and increases carbon monoxide

Babies can miscarry or be born low birth weight

Babies are shorter and 50 percent more likely to have intellectual disability

FETAL ALCOHOL SPECTRUM DISORDER (FASD) is a disorder caused by the pregnant mother consuming substantial quantities of alcohol during pregnancy, potentially resulting in mental retardation, delayed growth, and facial deformities.

Even smaller amounts of alcohol can produce FETAL ALCOHOL EFFECTS (FAE), a condition in which children display some, although not all, of the problems of FAS due to their mother’s consumption of alcohol during pregnancy.

The Prenatal Environment: Threats to Development (5 of 5)

LO 2.9 Describe the threats to the fetal environment and what can be done about them.

Do Fathers Affect the Prenatal Environment?

Secondhand smoke

Alcohol and illegal drug use can lead to chromosomal damage at conception

Stress may be unhealthy for mother

Sperm damage from environmental toxins

Becoming an Informed Consumer of Development: Optimizing the Prenatal Environment

Optimizing pregnancy

Planning

Schedule nonemergency X-rays only during first 2 weeks after menstrual periods

Get vaccinations 3 months before getting pregnant

Discontinue birth control pills 3 months before pregnancy

Eat well before and during pregnancy

Don’t use alcohol or other drugs

Monitor caffeine intake

Don’t smoke

Exercise regularly

Review: Prenatal Growth and Change (1 of 2)

Fertilization joins the sperm and ovum.

The germinal stage is fertilization to two weeks.

The embryonic stage is 2 to 8 weeks.

During the embryonic stage, the ectoderm, mesoderm, and endoderm grow and specialize.

The fetal stage is 8 weeks to birth.

The fetal stage is characterized by rapid increase in complexity and differentiation of organs.

Review: Prenatal Growth and Change (2 of 2)

Some couples need medical aid to conceive.

Options for infertility include IVF and artificial insemination.

A teratogen is a drug, chemical, or virus that produces birth defects.

Factors in the mother that can affect the unborn fetus are diet, age, and illness and drug, alcohol, or tobacco use.

The behaviors of fathers can affect the health and development of an unborn child.

Check Yourself: Prenatal Growth and Change (1 of 4)

The fertility treatment in which fertilization is induced inside the mother’s body is known as _________.

A) artificial insemination

B) intracervical insemination

C) intrauterine insemination

D) in vitro fertilization

Answer: A

Check Yourself: Prenatal Growth and Change (2 of 4)

Fertilization that occurs outside the mother’s body is called __________.

A) artificial insemination

B) infertility

C) in vitro fertilization

D) intracervical insemination

Answer: C

Check Yourself: Prenatal Growth and Change (3 of 4)

Match the following descriptions of prenatal development to their appropriate labels: germinal, embryonic, and fetal.

A) This stage lasts from 8 weeks until birth and involves the differentiation of major organs.

B) From 2 to 8 weeks following fertilization, when the major organs and basic anatomy begin developing.

C) The first and shortest stage, where the zygote begins to divide and grow in complexity during the first 2 weeks following conception.

Answer: A=fetal

B=embryonic

C=germinal

Check Yourself: Prenatal Growth and Change (4 of 4)

A __________ is an environmental agent such as a drug, chemical, virus, or other factor that produces a birth defect.

A) terminal button

B) teratogen

C) terrapin

D) chromosome

Answer: B

Applying Lifespan Development

Studies show that “crack babies” who are starting school have significant difficulty dealing with multiple stimuli and forming close attachments. How might both genetic and environmental influences have combined to produce these results?

Photo Credits

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