Hi, Thanks for the query. Usually after taking HCG injection, the ovulation can occur in around 36 to 40 hours. So if you have unprotected intercourse around this period the chances of fertility will increase. You can follow your doctor s advice. Start taking folic acid tablets from now-onwards. For more details you can ask me through: http://www.healthcaremagic.com/doctors/dr-sree-gouri-sr/63429 Take care.