Twins Flashcards
What are clinical associations for a twin pregnancy?
Large for gestational age (LGA), multiple heartbeats, SMAFP levels at > 2.5 MOM (multiple of median)
What are the membrane configurations with twins?
Chorionic and amniotic
What is dizygotic twinning?
The fertilization of 2 ovum (dichorionic/diamniotic)
What is dizygotic twinning influenced by?
Genetics, environment, age and ART
What is monozygotic twinning?
A random event resulting in single ovum division
What are placental and membrane configurations with monozygotic twins?
Varies and has membrane configurations of: Di/Di, Mono/Di, and Mono/Mono
What is the sonographic assessment for twins?
Fetal lie/number, # placentas, membranes? standard anatomy (biometry), AF - MVP (maximal vertical pocket), pulsed/color doppler
Which type of pregnancy has an increased rate of obstetric complications?
Monochorionic
What is dichorionic/diamniotic comprised of?
2 layers of chorion, 2 layers of amnion
How does Di/Di appear on ultrasound in the first trimester?
A thick echogenic layer of chorion surrounding each embryo
How does Di/Di appear on ultrasound in the 2nd/3rd trimester?
2 placentas, twin peak/lambda sign
How does the twin peak/lamda sign appear on ultrasound?
A wedge shape of chorionic tissue going into the base of the thick inter-twin membrane
What happens with the amnion after 14-16 weeks?
It’s no longer seen separate from the chorion
How does Mono/Di appear in the 1st trimester?
2 yolk sacs, embryos within same chorionic sac
How does Mono/Di appear in the 2nd/3rd trimester?
Thin inter-twin membrane, no twin peak sign, one placenta, same gender
What are the risks of Mono/Di pregnancy?
Twin-twin transfusion, evaluation of cord insertion for each twin
How does Mono/Mono pregnancy appear?
1 chorionic layer, 1 amniotic layer and 1 placenta
What is the majority problem with Mono/Mono pregnancy?
Cord entanglement (evaluate w/doppler)
How does Mono/Mono appear in 1st trimester?
2 embryos with 1 yolk sac (after 7 weeks)
How does Mono/Mono appear in 2nd/3rd trimester?
Same gender/no inter-twin membrane
What causes vanishing twin?
Spontaneous abortion, embryonic malformation, nonviable pregnancy (20%)
What is fetus papiraceus?
Death/preserved fetus due to compression
What are maternal complications from fetus papiraceus?
Increased mortality/cesarian, hypertension, postpartum hemorrhage
What are fetal complications from fetus papiraceus?
Low birth weight, congenital anomalies, vasa previa (overlying cervix, into amniotic membrane)
What is twin reversed arterial perfusion (acardiac twinning)?
An acardiac twin dependent on other (pump twin)
What happens in the placenta with acardiac twinning?
Anastomoses of arterial to arterial and venous to venous systems
What are sonographic findings in acardiac twinning?
Possible hydrops (pump twin), malformed fetus w/no cardiac structures and flow reversal in cord (acardiac twin)
What is twin to twin transfusion syndrome?
Blood shunting from arterial/venous anastomoses in shared placenta causing a perfusion imbalance between fetuses
Which type of pregnancy may have twin to twin transfusion syndrome?
Monochorionic and diamniotic
What are the amniotic fluid discrepancies in twin to twin transfusion syndrome?
Recipient twin has polyhydramnios, the donor twin has oligohydramnios
What happens to the donor twin with twin to twin transfusion syndrome?
Growth restriction, hypovolemic (dilated cardiomyopathy/pericardial effusion) and anemia
What happens to the recipient twin with twin to twin transfusion syndrome?
Macrosomic, hypervolemic (cardiomegaly, biventricular hypertrophy, tricuspid regurgitation) plethoric (red-faced) and possible hydrops
What are sonographic diagnoses for twin to twin transfusion syndrome?
Single placenta, same-sex, fluid volume discrepancy, and 20% weight difference
What type are the majority of conjoined twins?
Thoracopagus (thorax) and omphalopagus (abdominal wall) mostly female
What are conjoined twins the result of?
Late monozygotic division (mono/mono) after day 13
What must be differentiated with parasitic twin (fetus in fetu)?
Teratoma (malignancy) upper abdomen,
hemartoma (benign) lower abdomen
What occurs with selective reduction in Di/Di pregnancies?
Termination with multiples or birth defects by injecting potassium chloride into fetal heart or umbilical cord
