••• Chapter 7^ Multiple Gestations^81
❍ How much greater is the risk of cerebral palsy in twins and triplets compared with singletons?
Increased by 4 times in twins and 17 times in triplets.
❍ How much greater is the perinatal death rate for twins compared with singletons?
Three times greater for twins compared with singletons.
❍ How much greater is the perinatal death rate for monozygotic twins compared with dizygotic twins?
2.5 times greater for monozygotic twins compared with dizygotic twins.
❍ If one twin dies, what complications can occur to the surviving twin?
Recent evidence suggests that death or morbidity in the surviving twin is due to acute hypotension and
partial exsanguination into the dying twin. The surviving twin can develop renal cortical necrosis, multicystic
encephalomalacia, or disseminated intravascular coagulation.
❍ What percentage of twins are affected by intrauterine growth restriction?
14 to 25%.
❍ What criteria are used to diagnose intrauterine growth restriction in twins?
Estimated fetal weight below the 10% for a singleton gestation or when there is discordance of >20% between the twins.
❍ What antenatal monitoring should be done once intrauterine growth restriction has been diagnosed?
Serial ultrasounds with umbilical artery Doppler velocimetry, twice-weekly nonstress tests with supplemental
biophysical profiles. Early delivery should be considered if absent or reversed end-diastolic flow is discovered.
❍ What is the frequency of spontaneous reduction, or “vanishing twin”?
Ultrasound findings show 36% of twins, 53% of triplets, and 65% of quadruplets.
❍ What is the most common clinical presentation for a vanishing twin?
First-trimester bleeding.
❍ What is the pregnancy loss rate in multifetal reduction?
Pregnancy loss rates range from 5% to 25% depending on the starting number of gestations.
❍ What gestational age is multifetal reduction performed?
Multifetal reduction is performed around 10 to 12 weeks’ gestational age.
❍ What percentage of twin-to-twin contamination occurs when chorionic villus sampling (CVS) is performed
on a twin gestation?
Approximately 5% of cases.
❍ What is the positive predictive value of routine cervical exams or sonographic cervical measurements in
predicting preterm delivery?
75%.