••• Chapter 7^ Multiple Gestations^79
❍ After what gestational age does cord entanglement mortality become significantly reduced?
32 weeks.
❍ What physiologic effects can occur in twins affected with twin-to-twin transfusion syndrome?
Donor twin: Underperfused, anemic, growth restricted, microcardiac, hypotensive, and develops oligohydramnios.
Recipient twin: Overperfused, polycythemic, hypertensive, and develops polyhydramnios.
❍ What are the stages of twin-to-twin transfusion syndrome?
Stage 1: Donor twin bladder still visible, fetal Doppler values normal
Stage 2: Donor twin bladder no longer visible, fetal Doppler values normal
Stage 3: Donor twin bladder no longer visible, fetal Doppler values critically abnormal
Stage 4: Presence of hydrops
Stage 5: Intrauterine death of one or both fetuses
❍ What is the prognosis of twin-to-twin transfusion syndrome?
The earlier in gestation it develops the worse the prognosis. If diagnosed before approximately 28 weeks mortality
is 60% to 80%.
❍ What antenatal factors predict a poor outcome in pregnancies with twin-to-twin transfusion syndrome?
Early gestation at time of diagnosis, severe polyhydramnios requiring multiple therapeutic amniocenteses, hydrops
or absent or reversed end-diastolic flow.
❍ What is an arteriovenous shunt?
The most important anastomosis in twin-to-twin transfusion syndrome: A cotyledon is fed by the artery of one
twin and drained by the vein of the other twin.
❍ How does the incidence of twinning affected by age?
Increases with maternal age.
❍ The incidence of twins peak at what age?
35 to 40 years of age.
❍ What maternal changes are more frequently observed with multiple gestations?
(1) Anemia often develops secondary to a greater demand of iron from the fetuses
(2) Respiratory tidal volume is increased, but women pregnant with twins often feel “breathless,” possibly
secondary to a higher progesterone level
(3) Marked uterine distension and increased pressure on adjacent viscera.
(4) Theca-lutein cysts forms more frequently during multiple gestations as a result of higher levels of chorionic
gonadotropin
(5) Urinary tract infection is at least twice as common