Should luteal phase support be introduced in ovarian stimulation/IUI programmes? An evidence-based review

World-wide, intrauterine insemination (IUI) is still one of the most applied techniques to enhance the probability of conception in couples with longstanding subfertility. The outcome of this treatment option depends on many confounding factors. One of the confounding factors receiving little attention is the quality of the luteal phase. From IVF studies, it is known that ovarian stimulation causes luteal phase deficiency. Based on the best available evidence, this short review summarizes the indications for mild ovarian stimulation combined with IUI and the optimal stimulation programme. While it has been established that stimulated IVF/intracytoplasmic sperm injection cycles have deficient luteal phases, the question remains whether the quality of the luteal phase when only two or three corpora lutea are present (as is the case in stimulated IUI cycles) is impaired as well. There are too few large non-IVF trials studying luteal phase quality to answer this question. Recently a randomized trial has been published that investigated luteal phase support in an IUI programme. This study is discussed in detail. It is recommended to apply luteal phase support in stimulated IUI cycles only when proven cost-effective. Further trials are mandatory to investigate both endometrial and hormonal profile changes in the luteal phase after mild ovarian stimulation, and the cost-effectiveness of luteal support in IUI programmes.