Multifetal Gestations Flashcards
(37 cards)
Dizygotic (fraternal) twins
Two separate ova are fertilized by two separate sperm.
They are distinct pregnancies coexisting in the same uterus (each has its own amnion, chorion and placenta).
Monozygotic (identical) twins
A single fertilized ovum is cleaved at various stages during embryogenesis, therefore the arrangement of fetal membranes and placentas depends on which time the embryo divides.
How many chorions/amnions exist in monozygotic twins if cleavage occurs at 0-3 days?
How many twins have this placentation?
2 chorions and 2 amnions
30%
How many chorions/amnions exist in monozygotic twins if cleavage occurs at 4-8 days?
How many twins have this placentation?
1 chorion and 2 amnions
60%
How many chorions/amnions exist in monozygotic twins if cleavage occurs at 9-12 days?
How many twins have this placentation?
1 chorion and 1 amnion
1%
Which placentation is the most dangerous? Why?
What is at a high risk?
What is the net mortailty?
Monochorionic monoamniotic (9-12 days of cleavage) due to lack of separating amnions.
Cord entanglement
50-80% mortality
How many chorions/amnions exist in monozygotic twins if cleavage occurs at 13-15 days?
What is craniopagus vs. thoracopagus vs. ischiopagus? What are their incidences in this placentation category?
1 chorion and 1 amnion.
Craniopagus: joined at the cranium - 2%
Thoracopagus: joined at chest wall - 30-40%
Ischiopagus: joined at coccyx and sacrum - 6%
What percent of spontaneous twins are monozygotic twins vs. dizygotic twins?
Monozygotic: 1/3
Dizygotic: 2/3
What influences the development of dizygotic twins?
Maternal age: 2x more common in women >35 y/o
Family history and ethnicity (Asian
How is confirmation of multiple gestation made?
US
Which twin type is most likely to cause problems in pregnancy?
Monozygotic
What features suggest dizygosity on US? (3)
Different gender
Thick amnion-chorion septum
“Peak” or “inverted V” signat base of the septum
What feature suggests monozygosity on US?
The dividing membrane is fairly thin
If US is not definitive of zygosity, what should be done to determine it?
Placental inspection post delivery
DNA analysis
Interplacental vascular anastomoses occur in which twins? How commonly?
What is the most common type?
What complications can ensue?
90% of monochorionic twins
Arterial-arterial type
Aboriton, polyhydramnios, TTS, fetal malformations, etc.
What is TTTS?
What are the risks for each twin?
What is the prognosis?
Twin-twin transfusion syndrome - there is a net transfer of blood flow from one twin to another.
Donor twin: hypovolemia, hypotension, anemia, oligohydramnios, growth restriction
Recipient twin: hypervolemia, polyhydramnios, thrombosis, HTN, polycythemia, edema, cardiomegaly, CHF
Poor - both twins are at risk due to HF. If untreated, mortality is high.
What is the treatment of TTTS?
Serial amniocentesis with amniotic fluid reduction.
-can reduce preterm contraction secondary to uterine distention (polyhydramnios) and maternal symptoms
Laser photocoagulation of anastomosing vessels on the placenta is done at specialized centers.
What happens in arterial to arterial anastomoses in twins?
What is the “acardiac twin”?
Arterial blood flow from the donor twin enters the arterial circulation of the recipient twin. The reversed blood flow may cause thromboses within critical organs or atresia due to trophoblastic embolization.
The recipient twin, being perfused in a reverse manner with poorly oxygen blood, fails to develop normally.
- fully formed lower extremities
- no anatomic structures above the abdomen
Umbilical cord abnormalities are primarily associated with…
What structure is absent? What are they associated with?
Which cord abnormality is most common?
Monochorionic twins (monozygotic)
Absence of umbilical a. -> 30% associated with other congenital anomalies
Velamentous umbilical cord insertions
Retained dead fetus syndrome is associated with which twin type?
What can develop if gestation is >20 wks with a retained dead fetus?
What happens if there is a retained dead fetus < 12 wks?
What if there is a retained dead fetus > 12 wks?
Monozygotic twins
> 20 wks: DIC in the mom (check platelets and fibrinogen weekly)
< 12 wks: reabsorbed - “Vanishing twin syndrome”
> 12 wks: the fetus shrinks, dehydrates and flattens - fetus papyraceus
What is the antepartum management of twins in the first and second trimesters? (2)
Third trimester? (3)
1st and 2nd: 2 week office visits, US cervical length measurements.
Serial US to check for intrauterine growth q4-6 wks beginning at 24 wks.
-check for discordant fetal growth (20% less fetal weight in smaller fetus)
NSTs or weekly BPPs
Possible bed rest
A cervical length at which time doubles the risk for premature birth in twins?
25 mm at 24-28 wks
When should monoamniotic twins be delivered generally? Can it ever be delayed?
When does hospitalization begin? What is done at that time? (2)
When do most twins deliver? What is the OBGYNs preference?
At 32 wks (secondary to lethal cord entanglement)
Hospitalize at 26 wks and given antenatal steroids and FHR monitoring several times daily.
Most deliver at 35-36 wks, but the preference is to deliver at 38 wks.
What can be done for intrapartum management of twins? (7)
Delivery room equipped for emergent C-section
Large IV bore needle, blood products
FHR monitoring
Anesthesiologist available
US to determine precise presentations of twins
2 peds/NICU personnel (1 per baby)
Appropriate number of nurses
