Optimal Timing of Euploid Day 6 Blastocyst Transfer in Frozen HRT Cycles, Day 6 or Day 7 of Progesterone Administration.

Transvaginal ultrasound throughout the HRT cycle to not only monitor endometrial development but to also exclude the presence of an ovarian dominant follicle

In conjunction with ultrasound monitoring, participants will undergo serial measurements of serum Luteinizing Hormone (LH), Estradiol (E2) and Progesterone (P4) levels

"Participants will commence estradiol valerate 4 mg ( 2 x 2 mg) on day 2 / day 3 of menses.~Estradiol will be increased to 6 mg on day 2 of estrogen treatment, and continued at a daily dose of 6 mg (3 tablets daily)"

The initial progesterone dose of 100 mg will be commenced at 13hrs and repeated at 21hrs considered day 1 (vaginal suppository) when an optimal endometrial thickness for each participant has been achieved with a trilaminar appearance. The following day (day 2) progesterone administration will be increased to 100 mg vaginally three times daily

On the day of embryo transfer (ET), a blood test is taken to measure serum P4

Procedure in which embryo is transferred into the uterus