<prompt> A patient with twin pregnancy, USG done at 26 weeks of pregnancy shows a single placenta, first twin with AFI of 5 cm, fetal weight of 700 gms, bladder not visible, second twin with AFI of 16 cm, fetal weight of 1200gms. Diagnosis is?IUGR of first twin and normal second twinTwin reverse aerial perfusion syndromeAcardiac second twinTwin to twin transfusion syndrome  <response>: Twin to twin transfusion syndrome TTTS Occurs in monochorionic twin pregnancy. Cause is unidirectional blood flow through A-V anastomosis in a cotyledon shared by the two twins. Features: Discordant twins difference in fetal weight 20 with larger twins as reference Donor twin: oliguria, anemia, cardiac failure, IUGR, absent bladder Recipient twin: polyuria, hyperbilirubinemia, polyhydramnios, hydrops Poly-oli polyhydramnios in recipient -oligohydramnios in donor sequence 