Exam 2: Placenta phys/TWINNING

Question 1

Prelacunar stage (days 6-8)

Answer 1

• implantation of blastocyst

- differentiation of tblasts –> inner CTB, outer sCTBs

Question 2

do CTB divide? do sCTB divide?

Answer 2

CTB= inner layer, proliferate and eventually invade adjacent maternal tissue

sCTB= outer layer, NON MITOTIC

Question 3

lacunar trabecular stage (day 9-12)

Answer 3

implantation is complete

Question 4

villous stage (day 13-18)

Answer 4

appearance/ development of chorionic villi in 3 stages

Question 5

Primary Villi

Answer 5

CTB core surrounded by sCTB

develops in week 2

Question 6

secondary villi

Answer 6

extra-embryonic mesoderm core surrounded by CTB and sCTB

develops week 3

Question 7

tertiary villi

Answer 7

• formation of arterio capillary network
• core of villous (fetal) caps surrounded by CTB and sCTB
• will become VILLOUS CHORIAN aka fetal component of placenta

Question 8

floating villi

Answer 8

• nut/waste xchange

- majority of placental mass

Question 9

anchoring villi

Answer 9

• site of invasive CTB development

- attaches to uterus, makes contact with decidua

Question 10

CTB interstitial invasion –> CTB endovascular invasion

Answer 10

CTBs from anchoring cell column invade through decidua into inner 1/3 of myometrium –> remodel uterine spiral arteries

Question 11

what is the purpose of CTB invasion?

Answer 11

modify arterioles to become low resistance, high flow to prevent growth restriction

Question 12

route of O2 diffusion from mom to baby

Answer 12

maternal arterial blood in intervillous space –> sCTB layer –> CTB layer –> fetal endothelial cells of L umbillical v

Question 13

amniotic fluid

Answer 13

= ultrafiltrate of maternal plasma + fetal urine + fetal lung secretions

• 250ml at 16weeks to 1L at 32weeks, decreases from there
• critical for lung development and MSK fx

Question 14

causes of oligohydramnios?

Answer 14

• rupture of membranes
• congenital anomalies –> GU
• nephrotoxic drugs –> ACEi, NSAIDs
• poor placental perfusion

Question 15

causes of polyhydramnios?

Answer 15

• congenital anomalies –> NTD, esophageal atresia

- gestational diabetes

Question 16

diffusion limited transport

Answer 16

substances that cross placenta via diffusion cross SLOWLY

• RLS is characteristics of sCTB layer
• O2, CO2, H2O
• damage to sCTB can affect O2 to fetus!

Question 17

flow limited transport

Answer 17

• dependent on plasma concentration and rate of blood flow
• can be altered by decreased uterin bf –> dec placental perfusion –> decreased transport
• ex: pregnany woman with aortic stenosis

Question 18

why do we care about the types of placental transport

Answer 18

alterations lead to growth restricted fetuses

Question 19

hCG

Answer 19

• earliest preg marker, peaks at 10weeks
• maintain corpus lut and prog until week 8, placenta takes over
• regulates CTB –> sCTB diff

Question 20

hPL (human placental lactogen)

Answer 20

• produced by sCTB
• shifts maternal metab to fatty acid so carbs are available to fetus
• insulin resistance –> gestational diabetes

Question 21

placental growth hormone

Answer 21

• similar to pit GH
• control maternal IGF1
• secretion regulated by glucose
• **low levels in IUGR

Question 22

trophoblasts secrete _______

Answer 22

prog/est

Question 23

immune cell of the placenta

Answer 23

hofbauer cells in villous core

Question 24

what Ig does the fetus make? what Ig crosses?

Answer 24

• makes IgM
• IgG crosses via receptor mediated endocytosis
• flu vax/ Tdap to mom protects baby

Question 25

maternal fetal placental unit

Answer 25

- req for steroid hormone synthesis - placenta lacks P450c17, 16aOHase - Fetus lacks P450 aromatase and 3bOH-dh

Question 26

dizygotic vs monozygotic

Answer 26

di: 2 ova, 2 sperm; 70% of spont twins, 95% of ART mono: 1 ovum, 1 sperm; 30% of spont twins

Question 27

dichorionic, diamniotic chorionicity

Answer 27

- cleavage at 0-4 days - MONO OR DIZYGOTIC - separate chorionic cavities, amnion, placenta - 20-30% of monozygotics

Question 28

monochorionic diamniotic

Answer 28

- cleavage at 4-8 days - shared chorion, sep amnions, one placenta - only monozygotic - 70%

Question 29

monochorionic, monoamniotic

Answer 29

-cleavage at 8-12 days -shared amnion and chorion -only monozygotic 1%

Question 30

what do we worry about with mono/mono chorionicity?

Answer 30

cord entanglement - risk of mortality increase for BOTH babies - can't do much but admit mom to hospital and monitor fetal HR in case need to deliver emergently

Question 31

when do we see conjoined twins?

Answer 31

monochorionic, monoamniotic morula that splits after 13 days

Question 32

how to tell chorionicity on US?

Answer 32

di/di --> thick dividing membrane, twin peak/lambda sign mono/di --> thin dividing membrane, t sign mono/mono --> nothing

Question 33

what do we worry about with monochorionic diamniotic twins?

Answer 33

twin-twin transfusion syndrome (TTTS)

Question 34

what are risks of twinning?

Answer 34

- increase miscarriage in early preg - increased hyperemesis (from inc bhCG) - premies - anueploidy - prenatal screening is less sensitive, more difficult - gestational diabetes (inc hPL) - preeclampsia - PPH

Question 35

what is the average week of delivery for twins?

Answer 35

36 --> premie by definition.

Question 36

TTTS

Answer 36

- unbalanced flow through connected vessels - higher rate of discordance= higher rate of mortality - donor death --> increased risk of brain damage to reciever

Question 37

what type of vascular connection is implicated in TTTS?

Answer 37

artery/vein --> pressure difference | -can visualize with placental injection studies

Question 38

what do you see on US with TTTS?

Answer 38

donor baby: small, reduced urine --> OLIGO receiving baby: increases urine to reduce blood volume --> see large bladder, POLYhydro

Question 39

implications of untreated TTTS?

Answer 39

- mortality of one twin 80-90% - donor --> small placental vol, not enough nutrients to support fetal growth - recipient --> polyhyd, early delivery, fetal hydrops due to diffuse edema

Question 40

treatments for TTTS

Answer 40

1) reduction amniocentesis --> risk early delivery 2) microseptosomy --> create hole 3) laser ablation of anastomoses --> best survival rate