To find out if the percentage of endometrial compaction is correlated to clinical pregnancy rate in down regulated frozen embryo transfer cycle. Endometrial compaction is the change in endometrial thickness between the end of the estrogen only phase and the day of embryo transfer. In concept, the compaction of the endometrium after progesterone initiation indicates that the endometrium is responsive to progesterone and could therefore be used as a proxy for endometrial receptivity predictability of FET cycle outcome

Inclusion Criteria:

• Women undergoing down regulated cycles frozen embryo transfer.
• Women at age group 20-35 years old.
• Day 5 embryos will be transferred.

Exclusion Criteria:

• Chromosomal abnormality in either partner (As this could lead to cycle cancellation).
• Uterine malformation or any intrauterine condition affecting the pregnancy outcomes of FET, such as endometrial polyps, uterine cavity adhesion, history of endometrial tuberculosis, hydrosalpinx with a reflux into uterine cavity (As the might not be candidates for IVF cycle till correction).
• Recurrent implantation failure, defined as 2 or more previous failed trials (Other confounding factors might of present which could affect the results).
• Cycles of patients with persistent endometrial thickness <7mm during treatment protocol (Due to cycled cancelation).

Infertility patients planning for FET