Evolution of serum progesterone levels in the very early luteal phase of stimulated IVF/ICSI cycles post hCG trigger: a proof of concept study

Premature timing of progesterone luteal phase support initiation did not negatively impact live birth rates in modified natural frozen thawed embryo transfer cycles

“…In clinical practice, most investigators believe that ovulation occurs 36–48 h after hCG injection, so current studies often start using P 4 for LPS 48 h after hCG triggering [ 9 , 10 , 12 , 13 ], and some investigators administer it 36 h after hCG triggering [ 14 , 15 ]. However, it has been shown that hCG triggering leads to an increase in progesterone in the early luteal phase [ 16 , 17 , 18 ], which advances the implantation window and leads to asynchrony between the embryo and endometrium, which may lead to implantation failure [ 19 , 20 ]. Therefore, a limited number of researchers have decided that P 4 administration should take place 24 h after hCG triggering in order to prevent the issue of decreased endometrial receptivity to embryos brought on by early elevations of P 4 following hCG triggering [ 21 ].…”