Ans. is c i.e. 25% with the larger twin as index Unequal sizes of twin fetuses with a difference of 25% (larger twin being used as the index), is called as Discordant growth. It is a sign of pathological growth restriction in the smaller fetus. As the weight difference within a twin pair increases and the earlier the growth discordance is evident, perinatal moality increases. Most common cause of discordance : In dichorionic twins - unequal placental mass. mr,nochnrinnic ftviriS - Twin - twin transfusion syndrome/Genetic syndrome Hazards of discordant growth. The smaller fetus is at increased risk of perinatal moality due to : Respiratory distress Intra ventricular hemorrhage - Seizure Sepsis - Periventricular leukomalacia Necrotising enterocolitis At a difference of more than 30% - Risk of fetal death increases. Extra Edge : Besides weight - other ultrasonographic parameters indicating discordance. Difference in Bipanetal diameter is 6 mm or more. - Difference in Head circumference is 5% or more. - Difference in Abdominal circumference is 20 mm or more. On colour doppler ultrasound in umbilical aeries systolic to diastolic (S/D) ratio difference -is 15% or more. but amongst all cnterias best is Fetal weight difference i.e. more than equal to 25deg Route of delivery : In case of discordant growth vaginal delivery is indicated if - Cervix is ripe - Presentation is veex / veex - Weight of smaller twin is > 1500gms