Chapter 8 is one of the most important chapters in the entire textbook. If Chapters 3–6 explain how pregnancy begins, Chapter 8 explains how pregnancy is sustained. Nearly every complication you’ll study later—preeclampsia, fetal growth restriction, placental abruption, placenta previa, postpartum hemorrhage, diabetes, Rh disease—comes back to understanding the placenta.
If I were building a lifelong midwifery reference, this chapter would receive one of the largest sections.
Chapter 8 – Overview of Human Genetics and Genetic Disorders
- Read Coad, Anatomy & Physiology for Midwives, 4th edition, chapter 8.
- Write out your answers to Coad, Chapter Case Study, page 199.
- Create a Coad “Chapter 8 Study Sheet.” Include the following:
Learning Goals
□ Describe the development of the placenta, membranes, and umbilical cord.
□ Describe the anatomy of the placenta and umbilical cord.
□ Explain the functions of the placenta.
□ Explain the formation and functions of amniotic fluid.
□ Describe how abnormal placental development affects pregnancy.
□ Explain placental function in twin pregnancies.
□ Explain placental monitoring during pregnancy.
□ Describe how placental function influences fetal growth and long-term health.
Essential Vocabulary
Placental Development
- Trophoblast
- Chorion
- Chorionic villi
- Decidua
- Basal plate
- Chorionic plate
- Intervillous space
- Spiral arteries
- Cytotrophoblast
- Syncytiotrophoblast
Membranes
- Chorion
- Amnion
- Amniotic fluid
- Yolk sac
- Allantois
Umbilical Cord
- Umbilical vein
- Umbilical arteries
- Wharton’s jelly
- Cord insertion
Placental Conditions
- Placenta previa
- Placental abruption
- Placenta accreta spectrum
- Placental insufficiency
- Velamentous cord insertion
- Vasa previa
- Twin placentation
Draw
1. Placenta Cross Section
Label:
- maternal side
- fetal side
- chorionic villi
- intervillous space
- spiral arteries
- umbilical vein
- umbilical arteries
2. Maternal-Fetal Exchange
Draw:
Mother
↓
Placenta
↓
Baby
Show exchange of:
- oxygen
- carbon dioxide
- glucose
- amino acids
- antibodies
- wastes
3. Umbilical Cord
Label:
- two arteries
- one vein
- Wharton’s jelly
4. Placental Development Timeline
Blastocyst
↓
Implantation
↓
Trophoblast
↓
Chorionic villi
↓
Functional placenta
↓
Placenta delivered (third stage)
Structures & Concepts I Must Know
| Structure | Function |
|---|---|
| Chorion | Forms fetal portion of placenta |
| Amnion | Inner membrane surrounding fetus |
| Chorionic villi | Site of exchange |
| Spiral arteries | Maternal blood supply |
| Umbilical vein | Carries oxygenated blood to fetus |
| Umbilical arteries | Return deoxygenated blood to placenta |
| Wharton’s jelly | Protects umbilical vessels |
Placental Functions I Must Know
This table (8.1) is one of the most important in the chapter.
| Function | What the Placenta Does |
|---|---|
| Respiration | Exchanges oxygen and carbon dioxide |
| Nutrition | Transfers glucose, amino acids, fatty acids, vitamins, minerals |
| Excretion | Removes fetal waste products |
| Endocrine | Produces pregnancy hormones |
| Immunologic | Transfers IgG antibodies and helps protect the fetus |
| Protection | Partial barrier against some pathogens and toxins (but not all) |
I would memorize these six functions.
Hormones Produced by the Placenta
Know these well.
| Hormone | Primary Function |
|---|---|
| hCG | Maintains corpus luteum early in pregnancy |
| Progesterone | Maintains pregnancy |
| Estrogen | Uterine growth and blood flow |
| hPL | Alters maternal metabolism to supply the fetus |
| Relaxin | Softens connective tissue |
Processes I Must Understand
- Implantation
- Placental development
- Remodeling of spiral arteries
- Maternal-fetal exchange
- Placental hormone production
- Amniotic fluid production
- Placental aging
- Third-stage placental separation
Midwifery Connections
| Concept | Why a Midwife Cares |
|---|---|
| Placental function | Determines fetal growth and well-being |
| Placental location | Influences birth planning |
| Placental insufficiency | Fetal growth restriction |
| Placental hormones | Affect maternal physiology |
| Umbilical cord | Fetal circulation |
| Placental delivery | Third-stage management |
| Cord abnormalities | Potential fetal compromise |
Clinical Connections
Understand:
- Why placenta previa causes painless bleeding.
- Why placental abruption causes painful bleeding.
- Why poor placental perfusion contributes to fetal growth restriction.
- Why abnormal placentation is associated with preeclampsia.
- Why smoking reduces placental oxygen delivery.
- Why Rh antibodies cross the placenta.
- Why some infections cross the placenta while others do not.
- Why placental location is reassessed later if it is low-lying at the anatomy scan.
Things Worth Memorizing
- Two umbilical arteries.
- One umbilical vein.
- Major placental functions.
- Major placental hormones.
- Maternal and fetal blood normally do not directly mix.
- Chorion = outer membrane.
- Amnion = inner membrane.
- Wharton’s jelly protects the cord vessels.
- Human placenta is hemochorial, meaning maternal blood is in direct contact with the chorionic villi.
Questions I Should Answer Without Looking
- What are the six major functions of the placenta?
- Which blood vessel carries oxygenated blood to the fetus?
- Why don’t maternal and fetal blood normally mix?
- What hormones does the placenta produce?
- What is Wharton’s jelly?
- What causes placental insufficiency?
- Why does fetal growth restriction occur?
- What is placenta previa?
- What is placental abruption?
- Why is placental location important?
Compendium Entry
This chapter deserves five pages in your Midwifery Compendium.
Page 1 – Placental Development
- Timeline
- Implantation
- Trophoblast
- Chorionic villi
Page 2 – Placental Anatomy
- Maternal side
- Fetal side
- Cord insertion
- Membranes
- Umbilical vessels
Page 3 – Placental Functions
- Gas exchange
- Nutrition
- Waste removal
- Hormones
- Immunity
- Protection
Page 4 – Placental Disorders
Include brief summaries of:
- Placenta previa
- Placental abruption
- Placenta accreta spectrum
- Placental insufficiency
- Vasa previa
- Velamentous cord insertion
Page 5 – Twin Placentation
Summarize:
- Dichorionic/diamniotic
- Monochorionic/diamniotic
- Monochorionic/monoamniotic
- Twin-to-twin transfusion syndrome (overview)
Quick Reference Cards
This chapter naturally lends itself to a number of cards you’ll likely use throughout training and practice:
- Placental Functions
- Placental Hormones
- Umbilical Cord Anatomy
- Placental Circulation
- Placenta Previa
- Placental Abruption
- Placenta Accreta Spectrum
- Placental Insufficiency
- Amniotic Fluid
- Twin Placentation
- Umbilical Cord Variations
One study technique I’d add for this chapter
Instead of viewing the placenta as just another organ, think of it as a temporary life-support system for the fetus. Ask yourself, “If the placenta can’t do this job well, what happens to the baby?”
| Placental Job | If It Fails… |
|---|---|
| Oxygen exchange | Fetal hypoxia, abnormal heart rate, possible stillbirth |
| Nutrient transfer | Fetal growth restriction |
| Waste removal | Fetal metabolic stress |
| Hormone production | Pregnancy may not be maintained normally |
| Immune regulation | Increased risk of maternal-fetal immune complications |
| Blood flow | Preeclampsia, placental insufficiency, fetal compromise |
That way of thinking connects placental physiology directly to clinical practice. As you move into later chapters on fetal growth, hypertensive disorders, diabetes, and labor, you’ll see many complications as consequences of placental function—or dysfunction—rather than as isolated conditions. This systems-based understanding is what experienced midwives develop over time, and it makes the material much easier to integrate.
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