<prompt> Cordocentesis is done in which period of pregnancy?11-14 weeks18-20 weeks26-28 weeks28-32 weeks  <response>: Cordocentesis or percutaneous umbilical blood sampling PUBS- Done after 18 weeks Invasive procedure Gives results in 24-48 hrs punctured near the inseion at the placental end Uses - Fetal anemia assessment remains the most common indication. Assessment and treatment of platelet allo-immunization and for fetal karyotype determination 