This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Antenatal Screening, Subject name: Gynaecology & Obstetrics
Chorionic villous sampling done before 10 weeks may result in - 
Select and explain. 
A. Foetal loss, B. Fetomatemal haemorrhage, C. Oromandibular limb defects, D. Sufficient material not obtained
C: Oromandibular limb defects
Answer: C: Oromandibular limb defects 
Explanation: Ans. is 'c' ie Oromandibular limb defects " Chorionic villous sampling is usually performed at 10-13 weeks and is associated with several complications but studies suggests that limb reduction and oromandibular limb hypogenesis is more common if CVS is done before 9 weeks so CVS is done after 9 wks because it is more safe" - Williams, 21/e, p990NoteDon't get confused by what Harrison states on page 399, 15/e" There is an increased association of limb defects when the procedure in performed later (>=11 weeks of gestation)"Harrison is wrong here !