Objective: To investigate the relationship between elevated serum progesterone levels (EP) on the day of ovulatory trigger, live birth rates, and the growth of resulting embryos. Methods: A total of 836 in vitro fertilization (IVF) cycles with 4 478 embryos in conventional culture were retrospectively analyzed, together with an additional 90 IVF cycles producing 618 embryos from culture and assessment using the Embryoscope? time-lapse system. Results: In cycles using conventional culture, serum progesterone per follicle ≥14 mm (median 0.42 nmol/L/follicle, range 0.05-3.50 nmol/L/follicle) was a significant negative predictor of live-birth (ROC AUC = 0.395, 95% CI 0.345-0.445; P=0.000) as were progesterone/estradiol ratio (0.442, 0.391-0.494; P=0.027) and progesterone per oocyte (0.374, 0.326-0.421; P=0.000) but not progesterone alone (0.470, 0.419-0.521; P>0.05). Women with an EP/follicle (>0.42 nmol/L/follicle) had reduced live birth rates if they were ≥35 yrs (14.4% vs. 24.2%, P<0.05) but not <35 years (35.3% vs. 37.4%, ns). Despite reduced pregnancy rates, cycles with EP/follicle in women ≥35 years produced similar proportions of “good” and “top” quality embryos inconventional culture compared to women with low progesterone/follicle, and no difference in abnormalities of cleavage (direct cleavage or reverse cleavage), multinucleation or timings of division (pronuclear fading to 2-cell, 3-cell, 4-cell and 5-cell; cc2 and S2) observed with time-lapse videography. Conclusions: EP/follicle ≥14 mm (>0.42 nmol/L/follicle) adversely affects embryo implantation in women aged ≥35 years, but not <35 yrs. However, no adverse features were seen in the embryos from these affected cycles in terms of morphological appearance, abnormal patts of cleavage, or morphokinetic timings.