Ultrasound in the evaluation of normal and induced ovulation.

In the past several years sonography has become an invaluable research tool for the investigation of spontaneous and induced ovulation and has added to the understanding of folliculogenesis and reproductive endocrinology. In practical terms, in ovulation induction sonography assists in the evaluation of the number and distribution of follicles, necessary for adequate interpretation of estrogen levels. Although there is no ideal size when it can be assumed that a follicle is mature, estimation of follicle size is of value and is a good guide to the timing of hCG administration. If the follicles are extremely small or there is evidence of hyperstimulation, these observations, together with the E2 levels, may be used to decide whether a further ultrasonic examination is warranted for the assessment of follicular growth or whether the treatment cycle should be abandoned. Provided follicular size is within normal limits, the diameter of the largest follicle may also be used in IVF programs to determine when the patient should be admitted to the hospital for more intensive monitoring of follicular development and the administration of hCG. Ultrasound is also valuable in patients with only one ovary accessible to laparoscopy. Even if the largest follicle is in the inaccessible ovary, the treatment cycle does not have to be abandoned, provided that several follicles are developing in the contralateral ovary. If neither ovary is accessible laparoscopically, percutaneous oocyte aspiration offers the patient the opportunity of IVF and embryo transfer.