The Placenta Flashcards
What is the origin of the word ‘placenta’?
Derived from Latin for cake, Greek for flat, slab-like, and German for ‘mother cake.’
What is the normal term weight of the placenta?
Approximately 450 grams.
How much blood flows to the placenta at term?
600–700 ml/minute.
Name three functions of the placenta.
Oxygen/CO2 exchange, nutrient delivery, and waste removal.
What are the two separate circulations in the placenta?
Maternal-placental (uteroplacental) and fetal-placental (fetoplacental).
By what mechanisms do gases and nutrients exchange in the placenta?
Passive diffusion, facilitated diffusion, active transport, and endocytosis/exocytosis.
Name one abnormality affecting nutrient transfer in the placenta.
Maternal hypoxia or hypercarbia.
What hormones are synthesized and secreted by the placenta?
hCG, human placental lactogen, progesterone, and estrogens.
What is the role of uteroplacental circulation?
Maternal blood flows into the intervillous space to exchange oxygen and nutrients.
What do umbilical arteries and veins do?
Umbilical arteries carry deoxygenated blood from the fetus, and the umbilical vein carries oxygenated blood to the fetus.
What percentage of uterine blood flow at term is directed to the placenta?
90%.
What are Doppler studies used for in pregnancy?
To evaluate the blood flow and health of the placenta and fetus.
What does absent diastolic flow in Doppler studies indicate?
Severe reduction in blood flow from the fetus to the placenta.
Define placenta previa.
A condition where the placenta covers the cervix.
Define placenta accreta.
Placenta invades the myometrium without penetrating its full thickness.
What is placenta percreta?
The placenta penetrates through the myometrium and can attach to other organs.
What factors increase the risk of placenta accreta?
Uterine scars, previous C-sections, or placenta previa.
Why is pathological examination of the placenta important?
To clarify causes of adverse outcomes and assess risks for future pregnancies.
What percentage of placentas are submitted for pathology in some hospitals?
Between 50-100% in hospitals with established criteria.
Name one issue in OB-Pathology communication.
Poor understanding of terms used by each service.
What is the significance of Doppler studies in late pregnancy?
They show increased blood flow in diastole, indicating decreased placental resistance.
What maternal conditions indicate the need for placental examination?
Hypertension, diabetes, preterm or post-term delivery, and infections.
What neonatal conditions indicate the need for placental examination?
Stillbirth, growth restriction, congenital abnormalities, and infection.
How does smoking affect placental blood flow?
It causes vasoconstriction, reducing blood flow.
What is the maternal side of the placenta responsible for?
Maternal blood flow enters through spiral arteries and exchanges gases and nutrients in the intervillous space.
What is the fetal side of the placenta responsible for?
It allows umbilical arteries and vein to transport fetal blood for gas and nutrient exchange.
What is the maternal mortality rate for placenta percreta?
Approximately 10%.
What is the most common cause of placental edema?
Maternal diabetes or infection.
What percentage of uterine blood flow at term does estrogen-induced vasodilation support?
A 40% increase in maternal blood volume supports placental blood flow.
What is the legal importance of placental examination in adverse outcomes?
It clarifies causes, assesses acute vs. chronic insults, and may determine liability.
