This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Intra Uterine Growth Restriction, Intrapaum and Antepaum Fetal Surviellance, Subject name: Gynaecology & Obstetrics
Cordocentesis is done in which period of pregnancy? 
Select and explain. 
A. 11-14 weeks, B. 18-20 weeks, C. 26-28 weeks, D. 28-32 weeks
B: 18-20 weeks
Answer: B: 18-20 weeks 
Explanation: 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