Practical 3: placentation and twinning Flashcards
What is the difference in function of the syncitio and cytotrophoblast?
syncitio –> produces hormones + is invasive
cytotrophoblast –> proliferative
What does the maternal side of the placenta have and why are these present?
10-15 cotyledons due to decidual septa
what hormonal functions does the placenta have?
Progesterone
oestrogen/estriol
hCG (1st 2mths)
placental lactogen (somatomammotropin)
What is the function of somatomammotropin?
Gives the fetus priority of maternal glucose (mother diabetogenic) and stimulates breast lactiferous duct development
How does gas exchange occur across the placenta?
simple diffusion across the membrane between fetal and maternal vessels
Apart from O2, CO2 and hormones, what other substances cross the placenta?
FFAs, CHOs, AAs
vitamins
immunoglobululins (maternal antibodies)
How can you screen for rhesus sensitisation? How can it be prevented?
Blood test on 1st maternal visit. Rh -ve mothers can be given prophylactic anti-D antibodies at 28/40 and w/in 72 hrs of delivery
How does prophylactic Anti-D antibodies work?
Destroys fetal RBCs that have entered maternal circulation
When do the umbilical arteries and vein close?
Arteries: shortly after birth (functionally) but lumen closes after 2 mths
vein: shortly after umbilical arteries
when should the ductus arteriosus close
should close immediately after birth due to decrease of prostaglandins as ^ O2
Why are NSAIDs contraindicated after 30w pregnancy?
Ductus arteriosus premature closure (as PGs decreased)
How does gestational trophoblastic disease hydatidiform moles arise?
partial mole –> 69 chromosomes (2 sperms fertilising 1 egg)
complete mole –> 46 chromosomes (1 sperm duplicatiing or 2 sperm fertilisaing empty egg)
What are the risk factors for gestational trophoblastic disease?
Previous, age (<16 or >45), multiple pregnancy, women w/ hX OF AGE 12 MENARCHE/ocp USE/LIGHT MENSTRUATION, asian women
how can you detect gestational trophoblastic disease prenatally?
^^^ hCG
USS (snowstorm appearance)
biopsy (definitive)
what might hydatidiform moles progress to?
Invasive molar pregnancy (malignant)
What are the risk factors for placenta previa?
uterine surgery / c-section, previous, smoking, cocaine, ^ maternal age, uterine abnormalities (e.g. fibroids, congenital), large placenta (twins), multiparity
What are the possible consequences for placenta previa?
APH
Failure of head to engage –> c section
preterm delivery
…
What are the risk factors for placenta accreta?
smoking, multiparity, uterine surgery, advanced maternal age, asherman’s syndrome…
What are the 3 types of placenta accreta?
Accreta
increta
percreta
What are the possible consequences placenta accreta?
PPH after delivery (blood loss, DIC, multiple organ failure, death…) [notice previa is assoc. w/ APH]
hysterectomy
what is the problem with placenta abruption?
Shock w/out visible blood loss
What are the risk factors for placental abruption?
pre-eclampsia, smoking, thrombophilias, prev c section, trauma (e.g. fall or car accident)
what is placental abruption?
separation of the placenta from the uterine wall causing a build up of blood in the space
can be hidden or exposed
How is placental abruption managed?
ABCD approach (manage blood loss)
emergency c section if fetal distress
monitor for PPH
What are the implications of velamentous insertion of the umbilical cord if not picked up on USS?
if blood vessels overlie the cervix –> can rupture during ROM –> may cause fetal death
What can velamentous cord insertion cause?
If the vessels overlie the cervix –> vasa previa (which can rupture –> blood loss + fetal demise)
What is pre-eclampsia?
condition w/ HTN + proteinuria
How common is pre-eclampsia?
affects 5% of pregnancies
What are the risk factors for pre-eclampsia?
previous, multiple pregnancy, obesity, multipraity, FHx, DM, HTN, hydatidiform moles
What are the symtpoms of pre-eclampsia?
headache, visual problems, convulsions, respiratory (chest pain, cough, dyspnoea), decreased urine output, RUQ pain
what is HELLP syndrome?
A complication of pre-eclampsia (life-threatening)
Haemolysis (anaemia), elevated enzymes (LDH/AST/ALT), low platelet count
Pre-eclampsia management?
Regular maternal and fetal monitoring (e.g. bloods, USS, dOPPLER USS, CTG)
HTN control: labetalol (or nefidipine)
If BP very high –> (prophylactic) anticonvulsants
plan delivery (+ stay for few days post-delivery)
What is thought to be the major underlying cause of pre-eclampsia?
failed or incomplete differentiation of the cytotrophoblast cells (don’t undergo endothelial transformation)
invasion of maternal blood vessels is rudimentary
spiral arteries remain high resistant (small lumen)
what is eclampsia?
1+ convulsion superimposed on pre-eclampsia
ABCDE (resusc) magnesium sulfate (Rx seizure) Rx HTN: IV labetalol IV fluids/urine output delivery only when mother stable (i.e. stable, seizures controlled, HTN controlled)
What is cord prolapse? how is it managed until expert help arrives?
When UC herniates out of uterus w/ or before the presenting part of the fetus
is you see the cord push baby up to relieve pressure on cord to prevent hypoxia / brain damage
define monozygotic twins?
Twins that arise from the splitting of 1 zygote
Can you get monochorionic dizygotic twins?
Yes if the placentas fuse (but the amnions are always separate)
how do dizygotic twins differ from monozygotic?
only share 50% of their genetic material (like normal brothers and sisters)
which body regions are conjoined twins most commonly connected?
Thorax, abdomen and sacrum
What is the function of oestrogen in pregnancy?
uterine growth
give 2 risk factors for vasa previa?
velamentous cord insertion (vessels not covered by umb. cord / amnion) succenturiate lobe (accessory placental lobe)
What is the incidence of placental abruption?
1/200
What types of placental abruption are there?
Complete abruption (concealed haemorrhage)
Partial abruption (concealed or revealed haemorrhage)
What process means women with placenta previa do not have it by 3rd trimester (resolves)?
trophotrophism
What placental problem is associated w/ cocaine?
Placenta previa
