Placenta Flashcards
Placental Architecture
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Chorionic Villi
Primary: 8 days, cytotrophoblasts core surrounded by syncytiotrophoblast Secondary: 2 wks, extraembryonic mesoderm forms villous core Tertiary: 3 wks, formation of arteriocapillary network
Trophoblast invasion
Interstitial: cytotrophoblasts invade entire endometrium & first third of myometrium Endovascular: invade uterine spiral arteries through myometrial segments
hCG
maintain corpus luteum & progesterone until the placenta can take over maintenance Peaks at wk 10 Regulates trophoblasts -> syncytiotrophoblasts Elevated in trisomy 21
human placental lactogen
by sCTB Direct shift to fatty acid metab so glucose for baby insulin resistance = may cause gestational diabetes
placental GH
12 wks to term Controls materal IGF-1 Regulated by glucose
Steroid hormones
Trophoblasts secrete estrogens and progesterone (suppresses uterine contractions) Requires interaction for production because placenta lacks P450c17 & 16-a-H Fetus lacks P450 aromatase & 3Bhydroxysteroid DH
Amniotic Fluid
Early = ultrafiltrate of maternal plasma Later = more fetal urine and lung secretions
Chorion/Amnion Divisions in Monozygotic twins
Di/Di = division day 1-3 (25%) - thicker membrane and twin peaks. Can also be dizygotic twins Mo/Di = day 4-8 (70%) - thin membrane & T sign Mo/Mo = day 9-12 Conjoined = Day 13-15
Twin Risks
Miscarriage Hyperemesis (high hCG) Prenatal screening less sensitive Increased risk aneuploidy & anomalies (3-5x) Preterm (avg 36wks) Increased perinatal mortality Growth restriction
Twin-Twin Transfusion Syndrome
15-20% of mo/di twins All have anastomosis, but only problem if just one or two = unidirectional flow Recipent: increase in urine production, large bladder, polyhydramnios Donor: smaller, reduces urine, oligohydramnios Untreated prior to 24 wks = mortality in 80-90% Can ablate with laser, reduction amniocentesis, microseptostomy if severe
