Placental Gas Exchange + Transition to Extrauterine Life Flashcards
umbilicus anatomy
2 arteries, 1 vein, Wharton’s jelly (protects and constricts)
facts and functions about placenta
low pressure system, approx 1lb at birth, consumes 500mls/min of blood
functions: nutrition synthesis, transport nutrients, remove waste, immunity and endocrine
placenta: fetal phase
arises from: embryonic sac (sperm/egg)
- chorionic villi from chorionic membrane invade endometrium
- develop epithelial layer and connective tissues containing arterioles/venules from umbilicus
placenta: maternal phase
arises from: endometrium
- intervillous spaces form in endometrium around chorionic vili and fill with maternal blood
4 layers of placental barrier
blastocyst –> trophoblast further differentiates into
- syncytiotrophoblast
- cytotrophoblast
- connective tissue/basal lamina of villi
- endothelium of fetal capillaries
placental barrier allows passage of
o2, co2, antigens, viruses, nutrients, IgG, chemicals
factors affecting placental transfer
- hemodynamics
- [nutrients], nature of substance, surface area
- vascular pathologies/shunts
- diffusion issues (i.e. thickened chorionic membrane)
- o2 consumption of placenta
- maternal hypoxia
- maternal hyperventilation (alkalosis shifts maternal O2-Hb curve left)
PO2
- intervillous spaces (maternal) = 50mmHg
- umbilical vein = 30mmHg
- umbilical arteries = 19mmHg
term fetus ABG values (o2, co2, pH)
umbilical artery:
19, 47, 7.36
umbilical vein:
30, 43, 7.39
placental pathophysiological conditions
- pre-eclampsia
- eclampsia
- HELLP
- placenta previa
- abruptio placenta
- placenta (accrete, increta, percreta)
preeclampsia
symptoms: maternal hypertension, proteinuria, headache
develops after 20 weeks, resolves post birth
pathogenesis: excretion of endothelial substances from placenta
complications: impaired blood flow to placenta, premature birth, stroke or seizure in mom, placenta abruptio
fetal health complications: related to gestational age and severity of maternal disease; IUGR, preterm delivery/still birth
treatment: anti-hypertensives, anti-convulsives, bedrest, hospitalization for monitoring, early delivery of baby (c-section)
eclampsia
further development of pre-eclampsia
symptoms of this stage: convulsive seizures or coma, cerebral aneurysm
HELLP (Hemolysis Elevated Liver enzymes Low Platelets)
develops late stage of pregnancy
symptoms: epigastric pain, malaise, N&V … progresses to headache, parenthesis, blurred visions, +/- edema, mild hypertension, ruptured liver, coma/seizure (now eclampsia) … DIC, renal failure, liver failure, stroke, pulmonary edema
treatment: monitor, early delivery/remove placenta, manage maternal BP, +/- blood transfusion
abruptio placentae
full/partial premature detachment of placenta from uterine wall, often triggers labour
symptoms: excessive bleeding/shock/poor clotting/DIC (maternal); still birth/premature/oxygen deprived (baby)
ethologies: smoking (90% risk), pre-eclampsia, abdominal injury/blunt force trauma
placenta previa
implants in lower portion of uterus (cervix or close to)
issues: bleeding risk, can’t deliver naturally
3 types: low implantation, partial previa, total previa
classification:
- grade 0: asymptomatic
- grade 1: vaginal bleeding with no signs of maternal/fetal distress
- grade 2: vaginal bleeding maybe, fetal distress
- grade 3: vaginal bleeding maybe, maternal shock, fetal compromise/death
placenta accreta, increta, percreta
issues related to severity of attachment of placenta to uterus; increasing depth of attachment from uterine wall to muscle to other organs
placenta accreta: too deep into uterine wall, part or all remains attached leading to blood loss, infection, sepsis; OR to scrape or hysterectomy
placenta increta: through wall and muscle layers of uterus, 15%; hysterectomy
placenta percreta: going into other organs like bladder, 5%
risk: previous c-section (uterine health/scar tissue)
multiple gestation
increased incidence/risk of:
- fetal mortality
- prematurity
- RDS
- congenital anomalies
- IUGR
- infection
