When does fertilization occur? Where?
3-4 days after ovulation
- Occur within Fallopian tube
Describe implantation
- Timeline (start/end)
- Stage that adheres/invades
- Begins 6-8 days post ovulation
- Completed 11-12 days post ovulation
- Blastocyst becomes adherent to and invades into the secretory endometrium
What is the blastocyst?
- Cell layers and differentiation
- Forms from the multicell morula at 4 days post ovulation
- Outer cell layer becomes the placental disc, chorion and villi
- Inner cell layer becomes amnion, umbilical cord and embryo
When does hCG become measurable?
8-10 days after fertilization (in serum)
What is the function of the placenta?
- Transport O2 and nutrients to and remove CO2 and waste from the fetus
- Physical barrier to transport to certain substances, drugs and infectious agents
- Immunologic barrier that prevents cell trafficking between mother and baby
Describe maternal and fetal blood flow and villous permeability of the placenta
Maternal blood flow
- Implantation, spiral arteries, blood pressure, hemoglobin
Fetal blood flow
- Placental size, fetal blood vessels: umbilical cord to villous capillaries
Villous permeability
- Maturation, basement membrane, stromal cellularity, edema, intervillous space
What is decidua? Function?
Decidua is endometrium that has been hormonally influenced by pregnancy
- Acts as a physical and immunologic barrier between placental (fetus) and uterine (maternal) tissues
- Nitabuch’s fibrinoid between decidua and villi
What is seen here?
Nitabuch's fibrinoid: between decidua and villi
Describe ectopic pregnancy
- Prevalence
- Most common location
- Presentation and timeline
- 1/150 pregnancies
- 90% in the fallopian tubes
- Presentation typ ~6 weeks after last missed menstrual period
- Rupture of tube and intraabdominal hemorrhage may be life-threatening
- Rarely extruded from fallopian tube intact to become an intraabdominal pregnancy
What is seen here?
Tubal pregnancy
What are consequences of intraabdominal pregnancy?
- Fetal compression
- Lithopedion
What is placenta previa?
Abnormally low implantation completely covering cervix
- Baby cannot be born vaginally; would have to go through placenta
What is the presentation of placenta previa?
- Antenatal, painless vaginal bleeding
Describe abnormally "deep" implantation
- Prevents what
- Occurs where
- Abnormal implantation prevents spontaneous separation of the placenta
- Occurs in areas of deficient or absent decidua (endometrium)
- Lower uterine segment or cervix
- Cornu of uterus where fallopian tubes insert
- Overlying scars, (previous c-section, myomectomy)
- Leiomyoma
What is placentra creta describing? Classes?
How much all/part of the placenta attaches abnormally to the myometrium
- Accreta: onto myometrium
- Increta: into myometrium
- Percreta: through myometrium
What is seen here?
- Accreta: onto myometrium
- Increta: into myometrium
- Percreta: through myometrium
Describe uterine rupture
- Prevalence
- __% occur after ____
- Mgmt/treatment
- Location
- Mortality risk
- 1/800-3,000 deliveries
- 20% occur after prior c-section
- 1/17,000-20,000 unscarred uterus
- Many need post partum hysterectomy to control bleeding
- >90% occur in lower uterine segment and frequently involves the cervix
- 50% perinatal mortality
- 4% maternal mortality
Describe the hemochorial placenta
What is seen here?
Basal plate of placenta with maternal vessels (at implantation site)
- 100 arteries and 50-200 veins
Describe the maternal intervillous space
- Timeline
- Blood volume
- Maternal arteries and veins directly enter the intervillous space after 8 weeks gestation
- The intervillous space will contain 400-500 ml of maternal blood in vivo
What becomes the umbilical cord? When?
The body stalk becomes the umbilical cord by the 7th post menstrual week
What are complications of short/long umbilical cords?
- Short cords (under 30-35 cm) are problematic at delivery; may reflect poor fetal movement
- Long cords (>70-100 cm) may cause increased cord accidents (be compressed, cause strangulation...)
Describe umbilical cord insertion issues
- If inserts at periphery, it's more prone to compression (markedly eccentric cords)
- Velamentous: cord has vessels unprotected by placental disc; easily ruptured (baby will bleed out)
What is Velamentous insertion
- Incidence
- Risks
- Incidence 0.5-1% of deliveries
- Increased risk for thrombosis or rupture of the unprotected vessels
- Ruptured vessel can result in fetal exsanguination in 3 minutes
Describe umbilical cord spiraling
- Benefits
- Degree/direction
- Problems causing increased/decreased spiraling
- Coiling prevents kinking
- 7:1 left (counter-clock-wise)
- Absent or decreased spiraling
- Single umbilical artery, fetal growth problems, aneuploidy, diabetes
- Increased spiraling
- Diabetes, preeclampsia, growth restriction, torsion, stricture, intrauterine fetal demise
Describe the umbilical vessels (typically)
- Number
- Associations
- Normally have two arteries and one vein
- Single artery occurs in 1% of all deliveries
- 20% associated with malformations
- Risk for poor fetal growth and may have intolerance of labor
What is seen here?
Umbilical cord (with vessels)- single artery?
Describe the umbilical vessels themselves
- Large muscular arteries
- Thin walled vein with internal elastic lamina
- No vasa vasorum
- No peripheral nerves
What are chorionic plate vessels? Describe them
- Each umbilical artery produces 8+ branches
- Arteries always cross over veins on placental surface
What is seen here?
Villi
