LAUSR

As fertility specialists, we tirelessly search for effective and patient-friendly treatment protocols to help individuals and families achieve their fertility goals with the highest satisfaction and least stress and discomfort. Frozen embryo transfer (FET) utilization is sharply increasing. Now, more than ever, FET protocols face appropriate scrutiny, with the goal of optimizing both patient experience and live birth rates. In the current issue, Labarta et al. (1) present their retrospective cohort analysis of good-prognosis European blastocyst FETs (approximately 70% donor egg) after preparation with micronized vaginal progesterone (MVP) (400 mg twice daily). They showed that patients who received individualized luteal phase support (iLPS)—adding subcutaneous progesterone 25 mg daily from the day of transfer onward—were associated with good live birth rates among women noted to have low serum progesterone concentrations on the day of embryo transfer. A low progesterone concentration was defined as <9.2 ng/mL, a threshold established in their prior analysis (2). They compared the rates of live birth and secondary outcomes between a group with adequate progesterone concentrations (R9.2 ng/mL) (continued with MVP alone), a study group with low progesterone concentrations on the day of FET (continued with iLPS), and a historical cohort of women with low progesterone concentrations who did not receive iLPS. Individualized luteal phase support for women with low serum progesterone concentrations was associated with equivalent live birth rates when compared with women with adequate progesterone concentrations (44.9% vs. 45%, respectively). However, when compared with a historical cohort of women with low progesterone concentrations on the day of transfer who did not receive iLPS, the live birth rates were statistically significantly higher (44.9% vs. 37.3%, respectively). While limited by its reliance on a historical rather than contemporaneous control group for its most relevant conclusions, the study provides clinically useful and reassuring information. The data indicate that the addition of subcutaneous progesterone may be able to ‘‘rescue’’ those FET cycles in which low serum progesterone concentration is encountered after vaginal-only progesterone preparation. The study is most relevant for European patients and practitioners, given that vaginal-only progesterone protocols are more commonly used for FET in Europe and that subcutaneous progesterone is not available in the United States. The question of whether serum progesterone concentration should be measured and/or acted upon in the setting of programmed FET is undoubtedly a ‘‘hot topic.’’ A recent meta-analysis of 21 studies evaluated FET outcomes on the basis of serum progesterone concentrations. The investigators concluded that lower serum progesterone concentrations were associated with lower ongoing pregnancy rates and higher miscarriage rates and suggested a threshold of 10