<s>[INST] My wife and I trying for a baby but till now no result. Yesterday we visited a gynaec and she asked my wife to take susten 300 from 16 th day of her cycle.her cycle started 12th this month and the doctor also told to have relation on 12th,13,14 &15 th day of cyclecoz the egg ruptured last during this time onlywhat is the use of susten 300 and please advise on getting pregnant [/INST] Hi welcome to Chat Doctor. I have gone through your question. Sustain is progestin containing medicine. It will help in luteal phase in maturing endometrium and help fetus in implantation. So sustain is generally prescribed in later phase of cycle. Fertile days are +/-3 days to ovulation. If you have ovulation on 14 then 11 to 17 are fertile days. Hope I answered your question. Would be happy to help you further. Take care. </s>