Hallow, Fertyl is clomiphene citrate. It is basically used for egg release (ovulation) where natural ovulation is a problem. It is in particular useful in Polycystic Ovarian Syndrome where the follicles are maturing to varied extent and still the ovulation failure is noted. Clomiphene citrate is also having antioestrogenic effect. So it may hamper growth of endometrium. Hence, in women where Endometrial growth is low, gonadotropin hormones may be preferred for induction of ovulation. Endometrial thickness between 9 mm to 13 mm has proved to be most conducive for implantation of fertilized ovum or blastocyst. Ovulation occurring when endometrium is just 5.7 mm is likely to end in no pregnancy . So long as the follicular size is concerned, it has been reported for many decades that the ova discharged from the follicles of size between 18 mm to 21 mm are the healthiest one and give maximum fertilization rate and continuation of pregnancy success rate. Progynova is a synthetic hormone replacement for oestrogen. It is used to build up the lining of the uterus in preparation for embryo transfer during a thaw cycle for women who do not ovulate regularly. Hence in your case, it might prove to be effective in building up the endometrium. However, you should not wait for the ovulation beyond the follicular size more than 21 mm. If it takes longer for the endometrium to grow, you may waste this cycle and start Progynova earlier in next cycle and have ovulation at proper follicular size. I hope this information is useful to you for further decisions. Dr. Nishikant Shrotri