Placental Development

Question 1

5 reasons why a baby might be small

Answer 1

Prematurity
Infection (like CMV)
Genetic
Constitutional (small parents = small babies)
Uteroplacental

Question 2

3 uroplacental reasons for a small baby

Answer 2

Smoking
Maternal disease
Abnormal placentation

Question 3

How far does the placenta invade normally?

Answer 3

Into 1/3 of the myometrium

Question 4

Hemochorial

Answer 4

Means the placenta is formed from 2 genetically distinct people
Maternal blood is in DIRECT contact with fetal CELLS (trophoblasts)

Question 5

Implantation requires 2 synchronous processes

Answer 5

Uterine preparation (decidual reaction)
Embryo development and the ability to interact with the endometrium

Question 6

Uterus
1. Proliferative
2. Secretory
Phases

Answer 6

1. Ovarian follicles secrete estrogens causing endometrium to proliferate and remodel
2. Increased levels of progesterone from corpus luteum stimulate thickening of the endometrium and forms glandular structures add increased vascularity to support an implantation

Question 7

How long is the endometrium receptive to a blastocyst for?

Answer 7

8-10 days after an LH surge (6-7 days after ovulation)

Question 8

Changes to the endometrium during implantation

Answer 8

Increase in cell size, change in cell shape, extensive development of intracellular organelles for protein synthesis and secretion, formation of intracellular junctions
Lipid and glycogen accumulation for energy

Question 9

Where in the uterus does the placenta usually implant?

Answer 9

The fundus

Question 10

Placenta previa

Answer 10

When the placenta implants over the cervix

Question 11

What structures form by day 5 of embryonic development? (3)

Answer 11

The inner cell mass (embryonic pole), blastocoel (fluid filled cavity), and outer cell mass (trophoblast)

Question 12

Trophoblasts become what 2 cell types

Answer 12

Cytotrophoblasts (then into villus and extravillus types)

Syncytiotrophoblasts (formed by fusion of cytotrophoblasts and invade the endometrium)

Question 13

Extravillous cytotrophoblasts

Answer 13

Invade the maternal spiral arteries
Remodel the maternal blood vessels in the placenta
By the third trimester they allow for an open low resistance way for the blood to flow (critical to development)

Question 14

How are spiral arteries remodelled?

Answer 14

By extravillous cytotrophoblasts
Converts a tight, thick walled muscular vessel into an open capacitance vessel that can accommodate the tremendous increase in maternal blood flow required to adequately nourish the placenta and fetus

Question 15

Pre-eclampsia

Answer 15

Shallow cytotrophoblast invasion
Don’t get the wide open capacitance vessels in the placenta that you need
Hypertension

Question 16

Some abnormalities that can arise from shallow invasion

Answer 16

Growth restriction
Prematurity
Abruptio placenta (separates before its meant to)
Preeclampsia
Stillbirth

Question 17

Placenta accreta

Answer 17

When there is pathologic deep invasion of the myometrium
Risk factors: prior C section (can implant into the scar) or placenta previa
Often undiagnosed until delivery and can lead to postpartum hemorrhage, hysterectomy, and even death

Question 18

The process of placental maturation includes…

Answer 18

Extensive branching of villi
Increased surface area available for exchange between mom and fetus
Closer approximation of maternal and fetal circulation
Increased uterine blood flow

Question 19

Placenta is bigger than the fetus until ___ weeks

Answer 19

16

Question 20

The villi in early pregnancy have __ layers. What are they?

Answer 20

3 layers
Syncytiotrophoblasts
Cytotrophoblasts
Fetal capillary endothelium
Also technically some CT for support

Question 21

The villi in later pregnancy have __ layers. What are they?

Answer 21

2 layers
Syncytiotrophoblasts
Fetal capillary endothelium
This is to decrease the distance between maternal and fetal circulations
Vessels also move to a more peripheral location (closer to the blood) and the villi become more branched and vascular

Question 22

Uterine blood flow at term is approximately…

Answer 22

700 mL per minute

Question 23

Antepartum hemorrhage can be due to…

Answer 23

Placenta previa
Abruptio placenta (can be chronic or acute)

Question 24

Postpartum hemorrhage

Answer 24

From uterine atony (failure of the uterine muscle to contract after delivery, so spiral arteries do not get squeezed shut)