The Placenta

Question 1

What is the origin of the word ‘placenta’?

Answer 1

Derived from Latin for cake, Greek for flat, slab-like, and German for ‘mother cake.’

Question 2

What is the normal term weight of the placenta?

Answer 2

Approximately 450 grams.

Question 3

How much blood flows to the placenta at term?

Answer 3

600–700 ml/minute.

Question 4

Name three functions of the placenta.

Answer 4

Oxygen/CO2 exchange, nutrient delivery, and waste removal.

Question 5

What are the two separate circulations in the placenta?

Answer 5

Maternal-placental (uteroplacental) and fetal-placental (fetoplacental).

Question 6

By what mechanisms do gases and nutrients exchange in the placenta?

Answer 6

Passive diffusion, facilitated diffusion, active transport, and endocytosis/exocytosis.

Question 7

Name one abnormality affecting nutrient transfer in the placenta.

Answer 7

Maternal hypoxia or hypercarbia.

Question 8

What hormones are synthesized and secreted by the placenta?

Answer 8

hCG, human placental lactogen, progesterone, and estrogens.

Question 9

What is the role of uteroplacental circulation?

Answer 9

Maternal blood flows into the intervillous space to exchange oxygen and nutrients.

Question 10

What do umbilical arteries and veins do?

Answer 10

Umbilical arteries carry deoxygenated blood from the fetus, and the umbilical vein carries oxygenated blood to the fetus.

Question 11

What percentage of uterine blood flow at term is directed to the placenta?

Answer 11

90%.

Question 12

What are Doppler studies used for in pregnancy?

Answer 12

To evaluate the blood flow and health of the placenta and fetus.

Question 13

What does absent diastolic flow in Doppler studies indicate?

Answer 13

Severe reduction in blood flow from the fetus to the placenta.

Question 14

Define placenta previa.

Answer 14

A condition where the placenta covers the cervix.

Question 15

Define placenta accreta.

Answer 15

Placenta invades the myometrium without penetrating its full thickness.

Question 16

What is placenta percreta?

Answer 16

The placenta penetrates through the myometrium and can attach to other organs.

Question 17

What factors increase the risk of placenta accreta?

Answer 17

Uterine scars, previous C-sections, or placenta previa.

Question 18

Why is pathological examination of the placenta important?

Answer 18

To clarify causes of adverse outcomes and assess risks for future pregnancies.

Question 19

What percentage of placentas are submitted for pathology in some hospitals?

Answer 19

Between 50-100% in hospitals with established criteria.

Question 20

Name one issue in OB-Pathology communication.

Answer 20

Poor understanding of terms used by each service.

Question 21

What is the significance of Doppler studies in late pregnancy?

Answer 21

They show increased blood flow in diastole, indicating decreased placental resistance.

Question 22

What maternal conditions indicate the need for placental examination?

Answer 22

Hypertension, diabetes, preterm or post-term delivery, and infections.

Question 23

What neonatal conditions indicate the need for placental examination?

Answer 23

Stillbirth, growth restriction, congenital abnormalities, and infection.

Question 24

How does smoking affect placental blood flow?

Answer 24

It causes vasoconstriction, reducing blood flow.

Question 25

What is the maternal side of the placenta responsible for?

Answer 25

Maternal blood flow enters through spiral arteries and exchanges gases and nutrients in the intervillous space.

Question 26

What is the fetal side of the placenta responsible for?

Answer 26

It allows umbilical arteries and vein to transport fetal blood for gas and nutrient exchange.

Question 27

What is the maternal mortality rate for placenta percreta?

Answer 27

Approximately 10%.

Question 28

What is the most common cause of placental edema?

Answer 28

Maternal diabetes or infection.

Question 29

What percentage of uterine blood flow at term does estrogen-induced vasodilation support?

Answer 29

A 40% increase in maternal blood volume supports placental blood flow.

Question 30

What is the legal importance of placental examination in adverse outcomes?

Answer 30

It clarifies causes, assesses acute vs. chronic insults, and may determine liability.