Ever since I started practising reproductive medicine and IVF ( which isn’t long – 2015 to be precise )
I realised few things
1) It is good to know the physiology …. it is always helpful in tweeking the limited number of available medicines to customise as per your patients physiology or pathology . You can always add on a fancy LH and HGH ….. it helps sometimes 

2) As a rule of thumb – younger your patients egg….. more are the chances of successful conception – no rocket science there.😊

3) A Good Embryologist and supporting team and good quality of the IVF lab are very crucial for attaining that 35-40 percent , otherwise the rates would be less than that.

4)Most importantly when God will be kind on which couple is ultimately the final determinant 🙏🙏

And for freshers who start ….. don’t get disheartened …… it is disheartening to see failures and you self doubt your capabilities….. because initially you have limited number of patients . Once your patient number increases and you see the results of your seniors , you realise even they don’t have much success than the routine 35 -40 percent . 
PGS / PGD is still in it’s infancy in India ( we will certainly get better as it becomes cheaper or more affordable and when embryologists get their fair share)…. so don’t get hassled if any one quotes ….. PGS sae to hamare 100 percent success rates haen .Not many counsel for it routinely 😐😐