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Twin Gestation

QuestionAnswer
Fertilization of 2 ova by 2 different fathers with only a short time between Superfecundation
Ovulation occurs when pregnancy already exists. One month difference in gestational age Superfetation
What are 2 types of twins? Monozygotic and Dizygotic
Maternal, occurs from fertilization of one egg. The egg divides into 2 zygotes after fertilization Monozygotic
What is the Monozygotic incidence around the world? 3.5 per 1,000 pregnancies
Fraternal, two ovum are released at ovulation. Each are fertilized and are different individuals with same parents Dizgotic
What is the Dizgotic incidence in different parts of the world? Nigeria 1 in 20-25 US 1 in 100 Japan 1 in 150
What is amniocity? Number of amniotic sacs
What is Chorionicity? Number of placentas
Are always diamniotic and dizygotic Dizygotic twins
May be either diamniotic or monoamniotic and dichorionic or monochorionic, depending on the time of cleavage Monozygotic twins
Means two placentas/sacs Di/amnicotic or chorionic
Means one Mono
Timing of events for trophoblast Differentiate at 4 to 6 days post-fertilization
Timing of events for amnion Differentiates at approx 8 days post-fertilization
If the zygote divides before 4-6 day it will be dichorionic and diamniotic this account for 1/3 of all monozygotic twins
If the zygote divides between 6-8 days it is monochorionic and diamniotic this accounts for 2/3rd of all monozygotic
If the zygote divides after the 8th day it is monoamniotic and monochorionic and accounts for less than 1% of monozygotic twins
If the zygote divides after day 13 you will have Siamese twins
Conjoined twins accounts for about 1 in 70,000 delivers in the US
Siamese twins may have more than a 3 vessel cord
Name four classifications of conjoined twins Thoracopagus Craniopagus (cephalic) Pygopagus (posterior) Ischiopagus (caudal)
Will have one placenta or two placentas? one sac or two depending on the time of cleavage Monozygotic
TROPHOBLAST CELLS IMMATURE, DIFFERENTIATES AT 4-6 DAYS POST FERT, THEY KNOW WHAT THEY WILL BECOME PLACENTA
On day 8th these cell know what they will become Amnion (sac) cells
It's important to note the number of placentas and amniotic sacs
two placentas may be laying close together so look at the location and gender of each twin
Record what two things for each twin Growth and measurements
With one amnotic sac, the umbilical cord may get twisted, rate of death is 50-70%
Pathology, a twin pregnancy is considered a High risk
Rare, occurs in monozygotic twins, they share a placenta wit each having their own umbilical cord. There is an arterio-venous shunt With in placenta. Arterial blood of one twin (the donor) is pumped into the venous blood of the other twin Twin to twin transfusion syndrome
Twin to twin transfusion syndrome risk factors Donor may become hydropic/anemic and grwoth retarded. Receipent may be normal orhydropic. Affects growth of both. Hydramnios in receipents sac. Donor may have 2 vessel cord and may be 20% difference in weight
What is the Stuck-Twin syndrome 1. One twin is in a severly oligohydramniotic sac 2. One twin is in a polyhydramniotic sac
Stuck-Twin syndrome is manages by serial amniocentesis and possible complications in survivors from sac
Selective Reduction of fetuses in Mult gestations is done in the 1st trimester, sac injected with potassium chloride to cause death
What is the selection process to reduce number of fetuses Anomalous fetus/small GS/monochorionic twins Both/Most accessible sac: high and anterior in the fubdus/ Do NOT select a predenting embryo/reduce # to twins
Joined at the chest, most common Thoracopagus
Joined at the head Craniopagus
Joined posteriorly at the back Pygopagus
Joined at the caudal of their bodies Ischiopagus
One twin does not have a heart, blood from donor pumps blood into the body of the Acardiac Monster
Acardiac Monster can cause CHF i donor twin
Created by: yovana2011
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