At what size are follicles considered mature?
Many doctors monitor follicle development during IUI cycles. Most trigger when the dominant follicle is within a certain size range. While there is always some difference in doctor preference, the norms are unmedicated 20-24mm, clomiphene citrate 20-24mm, FSH-only meds 17 or 18mm minimum, and FSH+LH would be 16 or 17mm minimum. It is possible for slightly smaller follicles, 14-15mm, to contain a viable egg. Also, follicles continue to grow until they release, usually at a rate of about 1-2 mm per day. A woman may ovulate more than one follicle in a cycle, but the releases will occur within 24 hours. When hCG is not used, only follicles close in size are likely to release. The use of hCG induces ovulation in about 95 percent of women, and will get most mature follicles to rupture.
