Week 4 · Chapter

Chapter 4 — Prenatal Development and Birth

Child Development Free sample edition

The module's primary reading · ~35–45 minutes · Objective 3 (describe prenatal development and birth: the germinal, embryonic, and fetal periods, teratogens and sensitive periods, birth, and the newborn's Apgar assessment), with Objective 1 (explain child development's domains, periods, and core questions (nature and nurture, continuity and discontinuity), the ecological systems model, and the major theories of development, describing what each theory explains and what it leaves out) and Objective 2 (describe research and observation methods with children — descriptive, correlational, and experimental designs; longitudinal and cross-sectional designs; running records, anecdotal records, checklists, and time and event sampling — and the ethics of consent, assent, and confidentiality) called back · Read it first this week; the lecture, the slides, the tutorial, the quiz, and the workshop all build on it.

In plain language

Every child's story starts before birth, in the months when the body is built from a single cell. This week you will follow the prenatal periods (the three stages of development before birth) and see how genes (the body's inherited instructions) and the environment work together from the very start. You will meet teratogens (substances or conditions that can harm development before birth) and learn why their timing matters. Then you will follow birth itself and the newborn's first check, the Apgar score (a quick rating of five signs at 1 and 5 minutes after birth). You will finish with two health definitions every caregiver hears: low birth weight (a baby who is small at birth) and preterm birth (a baby who arrives early).

Why you already care about this

Picture a family at a prenatal clinic visit. At one appointment, the nurse says "the embryo." A few months later, the same nurse says "the fetus." The family asks a fair question: did something change, or is it a new word for the same thing? Something did change, and by the end of this chapter you will know what.

Now picture a birthing room. A baby arrives, and within a minute someone on the birth team is looking at the baby's breathing, color, and movement and writing down small numbers. Four minutes later they do it again. A relative in the hallway hears "a 7" and worries. You will be able to explain what that 7 means and, as important, what it does not mean.

By the end of this chapter you will be able to: name the germinal, embryonic, and fetal periods and say what happens in each; explain genotype and phenotype and why genes and environment work together; explain why a teratogen's timing matters and quote the CDC's statement on alcohol during pregnancy exactly; describe the three stages of labor in words; total an Apgar score from its five signs and read it as a check on the newborn's condition, not a forecast; and tell low birth weight apart from preterm birth using the World Health Organization's definitions.

Carry this line with you: a newborn's score is a snapshot of minutes, not a forecast of years.

Where we are

Already covered: Week 1 gave you the domains, the periods, nature and nurture, and the running case; Week 2 gave you the theories, including sensitive periods; Week 3 taught you to keep what you observe apart from what it might mean.
This week: development before birth, birth itself, and the newborn's first assessment, with the running case's first record.
How they connect: this week uses all three: nature and nurture meet in the uterus, sensitive periods explain why a teratogen's timing matters, and the newborn record is written in two columns.
Where we're going next: Week 5, Infancy and Toddlerhood: Physical Development, follows the same child into the first two years of growth, reflexes, and motor skills.

Week 1 told you that child development runs from conception through adolescence, and that the prenatal period is the first period the course studies. It also said that nature (genes) and nurture (experience) always work together. Week 2 gave you ethology's idea of a sensitive period, a time of special readiness when experience has a large effect, with learning still possible afterward. Week 3 taught you to write an observation record in two columns, one for what the child did and one for what it might show. You will use every one of those tools in the next forty minutes.

1. Follow the three prenatal periods

Think about building a house. First the lot is chosen and the foundation is set. Then the frame goes up: walls, rooms, pipes, and wiring all take their basic shape. After that come months of finishing work, when the house grows into itself and every room gets ready to use. Development before birth follows a similar order.

Here is the course's definition, set off so you can find it when you review:

The prenatal periods are three approximate stages of development before birth:

The germinal period runs about the first two weeks, from fertilization to implantation, when the fertilized egg attaches itself to the wall of the uterus.
The embryonic period runs about weeks 3 to 8. This is when the major organs and body structures form.
The fetal period runs from about week 9 until birth. It is a time of growth and refinement of the structures that are already in place.

Notice the word "about" in each line. The week counts are approximate, and sources draw the edges a little differently. They are a map of the usual order, not a stopwatch.

Worked example — counting the embryonic period. The embryonic period covers about weeks 3 through 8. Count the weeks it includes: 3, 4, 5, 6, 7, and 8. That is 8 − 3 + 1 = 6 weeks. So in about six weeks the body plan is laid down, and everything after week 8 grows and refines that plan. In words: the shortest-sounding period does the most construction work.

Back at the clinic, the family's question now has an answer. "Embryo" is the word for the developing baby during the embryonic period. "Fetus" is the word from about week 9 on. The name changed because the work changed: from forming the major structures to growing and refining them.

Misconception check. Students often think the fetal period is when the major organs form, because it is the longest period and the one people talk about most. It is tempting to assume the longest stretch does the most building. The cure is the house: the frame goes up first. The major organs and body structures form in the embryonic period, about weeks 3 to 8; the fetal period is growth and refinement.

Memory hook: germinal settles; embryonic builds; fetal grows.

2. Explain how genes and environment work together

Picture a family preparing for a birth. One grandparent is tall, and someone at dinner says, "The baby is going to be tall, it's in the genes." Is that right? Partly. Genes matter, but so does everything that happens around them, starting in the uterus and continuing through childhood food, sleep, and health.

Two terms in words first. A gene is a unit of heredity that carries instructions the body uses to build and run itself. A chromosome is a threadlike structure in a cell that holds many genes. This course names these structures and stops there; it does not go further into genetics.

Here are the course's definitions of the pair you will use all term:

Genotype is a person's genetic makeup, the set of genes the person inherits.
Phenotype is the observable characteristics of a person, which result from the genotype interacting with the environment.

Worked example — reading height as a phenotype. Height is something you can see and measure, so it is part of the phenotype. Step one: the genotype contributes instructions that make a range of heights possible. Step two: the environment works on those instructions, from the prenatal environment to nutrition and health in childhood. Step three: the height the child reaches is the result of both. In words: the dinner-table prediction names only one of the two inputs.

This is Week 1's nature-and-nurture idea, made concrete. Nature and nurture work together; neither acts alone. The uterus is the first environment every person lives in, which is why prenatal development is a good place to see the two working at once.

Misconception check. Students often think genes alone set a trait, so a phenotype is "in the genes" and the environment only adds small touches. It is tempting because family resemblance is easy to see. The cure: a phenotype is, by definition, what results when the genotype interacts with the environment. Reading it as genes alone is the old error of treating nature and nurture as competing forces.

Pause and think. Choose one option and write two or three sentences.

(a) Think of a trait you can observe in yourself or someone you know, such as height or a talent. What might the genotype have contributed, and what might the environment have added?
(b) Think of a family saying such as "it runs in the family." Rewrite it so it names both genes and environment.

3. Explain why timing matters: teratogens and sensitive periods

A painter who spills water on a sketch in the first minute ruins the outline. The same spill on a finished, dry painting does far less damage. Timing changes what a single event can do. Development before birth works the same way.

Here is the course's definition:

A teratogen is a substance or condition that can harm prenatal development. Its effect depends on timing, dose, and the individual, and the embryonic period is generally the most sensitive time for the major structures.

Week 2 gave you the sensitive period idea from ethology: a time of special readiness, when experience has a large effect. Teratogens show the other side of that readiness. A structure that is forming is open to help and to harm, so the period when it forms is the period when a teratogen can do the most damage to it.

The course's pinned example is alcohol. The Centers for Disease Control and Prevention states: "There is no known safe amount of alcohol use during pregnancy." This course quotes that statement exactly, with its source, and never softens it into "a little is fine." It is the issuing body's guidance, not advice from this course about any one person.

The other half of the picture is prenatal care: the regular health care a pregnant person receives from health professionals before the baby is born. This course names prenatal care in words only. Questions about any one pregnancy belong with a health professional, not with a course.

Now walk the habit the course uses for every reading. What happened? A substance reached the developing baby. What concept does it show? A teratogen, with timing that matters. Which theory explains it? The sensitive-period idea from ethology explains why the same exposure can matter more at one time than another. What does a second theory add? Bronfenbrenner's ecological systems model adds the settings around the pregnancy. The family and clinic are the microsystem, a parent's workplace is the exosystem, and a culture's laws and customs are the macrosystem. All of them shape what reaches the baby and what care the family receives. The reading in one plain sentence: a teratogen's effect depends on timing, which the sensitive-period idea explains, and the settings around a pregnancy shape both the exposure and the care, which the ecological model adds.

Misconception check. Students often think a teratogen is equally harmful at every point in pregnancy, because "harmful is harmful." It is tempting because one word, harmful, seems to settle the question. The cure: a teratogen's effect depends on timing, dose, and the individual. The embryonic period is generally the most sensitive time for major structures. A caveat matters here too: "less sensitive" never means "safe," and for alcohol the CDC says there is no known safe amount.

Memory hook: what is being built is what can be harmed.

4. Describe birth: the three stages of labor

Think about moving out of an apartment. First you open the door wide enough for the furniture to fit. Then the big item goes through. Then you carry out the last boxes and close up. Birth has a similar three-part order.

Here is the course's definition:

Labor is the process of giving birth, described in three stages:

The first stage: dilation of the cervix. The cervix, the opening of the uterus, gradually opens so the baby can pass through. This is usually the longest stage.
The second stage: the birth of the baby. The baby moves through the birth canal and is born.
The third stage: the delivery of the placenta. The placenta, the organ that forms during pregnancy and passes nutrients and oxygen to the developing baby, is delivered after the baby.

You will see labor described in words here, with no durations given as rules. Every labor is different, and the length of each stage varies widely from one birth to the next.

Worked example — putting the stages in order. A family is reading a hospital handout the night before a planned birth. The handout lists three moments out of order: "the placenta is delivered," "the cervix opens," and "the baby is born." Step one: find the stage that makes room, the cervix opening, which is the first stage. Step two: the baby is born in the second stage. Step three: the placenta comes last, in the third stage. In words: open, birth, placenta.

Misconception check. Students often think labor ends when the baby is born, because the birth is the moment everyone remembers. It is tempting to count only two stages. The cure: the third stage, the delivery of the placenta, is part of labor too. Labor has three stages, and the baby's arrival is the second.

5. Total and read the Apgar score

Back in the birthing room, the birth team needs a fast, shared way to describe how a newborn is doing in the first minutes. A long paragraph would take too long. Five quick ratings, added up, do the job.

Here is the course's definition:

The Apgar score is the newborn's first check, from Apgar (1953), "A Proposal for a New Method of Evaluation of the Newborn Infant", Current Researches in Anesthesia and Analgesia. It rates five signs: heart rate, breathing effort, muscle tone, reflex response (or grimace), and skin color. Each sign is scored 0, 1, or 2, at 1 and 5 minutes after birth, so each total runs from 0 to 10. MedlinePlus, the National Library of Medicine's health site, states that a score of 7, 8, or 9 is normal, and a 10 is uncommon.

The table below gives the standard scoring for each sign, so you can match a description to a score.

The five Apgar signs and what each score of 0, 1, or 2 describes
Sign	Scored 0	Scored 1	Scored 2
Heart rate	absent	below 100 beats per minute	more than 100 beats per minute
Breathing effort	not breathing	slow or irregular, weak cry	good, strong cry
Muscle tone	limp	some bending of arms and legs	active movement
Reflex response (grimace)	no response	grimace	cry, cough, or sneeze, or pulls away
Skin color	blue or pale all over	body pink, hands and feet blue	pink all over

The running case's first record

This course follows one illustrative, unnamed child from birth to 15 years through eight observation records. Record R1 is the first. It is written the Week 3 way, with what was observed in one column and what it might show in the other.

Record R1 (illustrative): the child, newborn · hospital birthing room · Day 1 · 1 and 5 minutes after birth · recorded by a member of the birth team, with the family's permission.

Record R1 (illustrative): what was observed, set apart from what it might show
What was observed (scores and behavior only)	What it might show (interpretation)
At 1 minute: heart rate 2, breathing effort 2, muscle tone 1, reflex response 1, skin color 1	the 1-minute Apgar total, read against the normal range
At 5 minutes: heart rate 2, breathing effort 2, muscle tone 2, reflex response 2, skin color 1	the 5-minute Apgar total, and how the newborn changed between checks
Turns toward a touch on the cheek and opens the mouth	a newborn reflex, which Week 5 names and explains

Worked example — totalling record R1. Add the five sign scores at each check, then compare.

The 1-minute check: 2 + 2 + 1 + 1 + 1 = 7.
The 5-minute check: 2 + 2 + 2 + 2 + 1 = 9.
The change between checks: 9 − 7 = 2. Muscle tone rose from 1 (some bending of arms and legs) to 2 (active movement), and reflex response rose from 1 (grimace) to 2 (cry, cough, or sneeze, or pulls away). That is 1 + 1 = 2, which matches the change in the totals.
The gap from the maximum: the highest possible total is 5 signs × 2 = 10, so the 5-minute total of 9 is 10 − 9 = 1 below it. Skin color stayed at 1 (body pink, hands and feet blue) at both checks.
The range check: 7 is the low end of MedlinePlus's normal range of 7, 8, or 9, and 9 is its high end. Both totals fall in the normal range.

In words: the newborn in record R1 scored 7 at 1 minute and 9 at 5 minutes, both in the normal range. Those numbers describe how the baby was doing in the first minutes after birth, and they predict nothing about intelligence or later development.

In practice (your tools). In a free spreadsheet, type the five sign names in cells A2 to A6 and the five scores in cells B2 to B6. In cell B7, type =SUM(B2:B6) and press Enter to get the total. Put the 5-minute scores in column C and total them with =SUM(C2:C6), then type =C7-B7 in another cell to see the change. Always write the total out as a sum of the five scores too, so a reader can check each one.

Notice the honesty note built into the score, because you will need it every time you read one. It rates the newborn's condition at two moments. It says nothing about how the child will think, learn, or feel later, and the course never uses it that way. The relative in the hallway who heard "a 7" heard a score in the normal range.

Misconception check. Students often think the Apgar score predicts intelligence or later development, because a number feels like a grade. Others think a score of 7 is a problem, because 7 out of 10 sounds low. Both are tempting and both are wrong. The Apgar score assesses the newborn's condition at 1 and 5 minutes after birth, and MedlinePlus states that 7, 8, or 9 is normal; a 10 is uncommon.

Memory hook: five signs, two checks, a snapshot of minutes.

6. Tell low birth weight apart from preterm birth

Two newborns can be described with very different words. One family hears "born early." Another hears "small at birth." Those are two different measurements, and the World Health Organization defines each one.

Here are the course's definitions:

Low birth weight is a weight at birth of less than 2,500 grams.
Preterm birth is a baby born alive before 37 completed weeks of pregnancy.

One definition is about weight, and the other is about timing. Because they measure different things, a baby can meet one definition, both, or neither.

Worked example — sorting four illustrative newborns. Each newborn below is invented for practice; none is the running case.

Newborn W: born at 39 completed weeks, weighing 2,350 grams. 39 is not before 37, so not preterm; 2,350 is less than 2,500, so low birth weight. One definition.
Newborn X: born at 35 completed weeks, weighing 2,700 grams. 35 is before 37, so preterm; 2,700 is not less than 2,500, so not low birth weight. One definition.
Newborn Y: born at 34 completed weeks, weighing 2,100 grams. Preterm and low birth weight. Both definitions.
Newborn Z: born at 40 completed weeks, weighing 3,300 grams. Neither definition.

In words: always check weight against 2,500 grams and timing against 37 completed weeks as two separate questions.

Like the clinic nurse's two words, embryo and fetus, these terms name what you can see at one moment. These definitions describe a birth; they do not describe a child's future. Like the Apgar score, they are reasons for a health team to watch and support a baby, never a verdict the course draws about any child.

Misconception check. Students often think "preterm" and "low birth weight" are two names for the same thing, because early babies are often small. It is tempting because the two often appear together. The cure: preterm is about timing (before 37 completed weeks) and low birth weight is about weight (less than 2,500 grams). A baby born on time can be small, and a baby born early can weigh more than 2,500 grams.

The running case starts here. The newborn in record R1 is the same child you will meet at 9 months in Week 5, and at every period after that, up to 15 years. Every later record will be read the way you read this one: what was observed, what it might show, and what it does not.

Key terms

Prenatal periods — The three approximate stages of development before birth: the germinal period, the embryonic period, and the fetal period. (first used: 1. Follow the three prenatal periods)
Germinal period — The first prenatal period, about the first two weeks, from fertilization until the fertilized egg implants in the wall of the uterus. (first used: 1. Follow the three prenatal periods)
Implantation — The point, at the end of the germinal period, when the fertilized egg attaches itself to the wall of the uterus. (first used: 1. Follow the three prenatal periods)
Embryonic period — The second prenatal period, about weeks 3 to 8, when the major organs and body structures form. (first used: 1. Follow the three prenatal periods)
Fetal period — The third prenatal period, about week 9 until birth, a time of growth and refinement of structures that are already in place. (first used: 1. Follow the three prenatal periods)
Gene — A unit of heredity that carries instructions the body uses to build and run itself. (first used: 2. Explain how genes and environment work together)
Chromosome — A threadlike structure in a cell that holds many genes. (first used: 2. Explain how genes and environment work together)
Genotype — A person's genetic makeup, the set of genes the person inherits. (first used: 2. Explain how genes and environment work together)
Phenotype — The observable characteristics of a person, which result from the genotype interacting with the environment. (first used: 2. Explain how genes and environment work together)
Teratogen — A substance or condition that can harm prenatal development; its effect depends on timing, dose, and the individual. (first used: 3. Explain why timing matters: teratogens and sensitive periods)
Prenatal care — The regular health care a pregnant person receives from health professionals before the baby is born. (first used: 3. Explain why timing matters: teratogens and sensitive periods)
Labor — The process of giving birth, described in three stages: dilation of the cervix, birth of the baby, and delivery of the placenta. (first used: 4. Describe birth: the three stages of labor)
Placenta — The organ that forms during pregnancy to connect the developing baby with the pregnant person's body, and that is delivered in the third stage of labor. (first used: 4. Describe birth: the three stages of labor)
Apgar score — The newborn's first check, from Apgar (1953): five signs, each scored 0, 1, or 2, at 1 and 5 minutes after birth, for a total from 0 to 10. (first used: 5. Total and read the Apgar score)
Low birth weight — The World Health Organization's term for a weight at birth of less than 2,500 grams. (first used: 6. Tell low birth weight apart from preterm birth)
Preterm birth — The World Health Organization's term for a baby born alive before 37 completed weeks of pregnancy. (first used: 6. Tell low birth weight apart from preterm birth)

Summary

The germinal period settles, the embryonic period builds the major organs, and the fetal period grows and refines.
A phenotype results from the genotype interacting with the environment.
A teratogen's effect depends on timing, dose, and the individual.
The CDC: "There is no known safe amount of alcohol use during pregnancy."
Labor has three stages: dilation, birth of the baby, delivery of the placenta.
The Apgar score totals five signs, each 0, 1, or 2, at 1 and 5 minutes.
Record R1 scored 7 at 1 minute and 9 at 5 minutes, both normal.
Low birth weight is about weight; preterm birth is about timing.

Check your understanding

Work these before looking at the answers — they are ungraded, and the answers (with reasoning) are at the bottom of the page.

An illustrative newborn at a different birth is scored at 1 minute: heart rate 2, breathing effort 2, muscle tone 2, reflex response 1, skin color 1. Total the score and say whether it falls in MedlinePlus's normal range.
A pregnancy app (an illustrative example) says, "Week 12: your baby's major organs are forming now." Which period is week 12 in, and what is wrong with the sentence?
An illustrative newborn is born at 36 completed weeks and weighs 2,600 grams. Use the World Health Organization's definitions to say which, if either, applies.
A relative writes in a family group chat, "The baby got a 7 at one minute, so school might be hard for her." Name the wrong turn and rewrite the message so it is accurate.

Answers (worked reasoning — read after attempting)

Add the five sign scores: 2 + 2 + 2 + 1 + 1 = 8. MedlinePlus states that 7, 8, or 9 is normal, so 8 is in the normal range. In words: this newborn's 1-minute condition was in the normal range, and the score says nothing more than that.
Week 12 falls in the fetal period, which runs from about week 9 until birth. The major organs form in the embryonic period, about weeks 3 to 8, so by week 12 the work is growth and refinement. The sentence makes the classic wrong turn of placing organ formation in the fetal period.
Check timing and weight as two separate questions. 36 is before 37 completed weeks, so the birth is preterm. 2,600 grams is not less than 2,500 grams, so it is not low birth weight. One definition applies: preterm birth.
The message reads the Apgar score as a prediction of later development, and it also treats a 7 as a problem. An accurate version: "The baby scored a 7 at one minute, which is in the normal range. The score describes how she was doing right after birth; it does not predict anything about school."

Next up in this module: the Readings & Resources page, the lecture tutorial, the practice set, the quiz, the discussion, and the assignment — and next week, Infancy and Toddlerhood: Physical Development reads record R1's newborn reflex and uses the World Health Organization's windows model for motor milestones.

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