During this very important phase of the IVF cycle, our patients receive daily (occasionally twice daily) injections of gonadotropins – hormones, which stimulate your ovaries to produce multiple eggs. The common names for these gonadotropins are Follistim and Repronex. The “stim” phase of the cycle lasts on average 10 days, but can vary from 8 to 12 days, are necessary. At each visit blood will be drawn to study the change in your hormones and a vaginal ultrasound will be performed to note the progression of your ovarian follicles.

Our staff will make frequent reference about follicles – their number and size. Within each follicle is an egg. The egg is very small and cannot be seen on ultrasound. The fluid filled follicle surrounding the egg, however, is much larger and because fluid stands out on ultrasound, it is very easy for us to locate, count and measure the size of each follicle. Most importantly, the size of the follicle correlates with the maturity of the egg! The larger the follicle, the nearer the egg to being ripe and ready for harvest (a procedure we refer to as follicle aspiration, or retrieval). The egg within a follicle is usually mature – and ready for harvest- when the follicle measures between 16 and 20 millimeters.

Just before stimulation begins the follicles are usually small and often not visible and Estradiol (estrogen) levels are low. Large follicles (greater than 12mm) or elevated Estradiol levels at the start of stimulation usually indicates that a woman is not truly at day 3, and often necessitates postponing the cycle. A suppression check (a blood test and an ultrasound) is done in the days prior to the start of stimulation to ensure that all is ready. As stimulation progresses through the early stages (the first 5 days) the follicles usually show only minimal growth, but estrogen levels (measured as Estradiol) start to increase.

Soon thereafter, the follicles start to grow and once they reach about 12 to 14mm, they will grow fairly predictably at a rate of 2mm per day. During this phase of growth you will be monitored closely, sometimes as often as daily. Dr. Springer reviews lab results and follicle sizes after each visit. He also calls all of his patients later in the day to update them on any medication changes that need to be made. Frequently, the combined results of the ultrasound and the lab work will necessitate either slowing the cycle down (decreasing the dose of medication) or speeding it up (increasing the medication).

One of the problems in the early days of IVF was that dramatic rise in Estradiol would cause the eggs to “ovulate”, that is, to be released from the ovary. Once released, the egg can no longer be retrieved, and entire cycles were ruined. When Lupron became available, daily injections of this medication were found to suppress the tendency toward premature ovulation, thus allowing longer cycles and better quality eggs. For years, Lupron has been an essential part of the stimulation phase of IVF.

Recently, a new medication, Antagon, has become available. Antagon works similar to Lupron in that it suppresses premature ovulation. Antagon, however, is administered quite differently than Lupron. Lupron must be started 10 days before stimulation, and continued for the entire stimulation phase, a total of approximately 3 weeks. Antagon need only be given for the last 4 to 5 days of the actual stimulation cycle. The majority of our patients are now using Antagon, although in select cases, Lupron still offers advantages. The major advantage of Antagon is that it helps to simplify an already tedious process. Dr. Springer will advise you regarding the use of either Lupron or Antagon.

The ultimate goal of IVF stimulation is to achieve the maximum number of mature follicles- eggs-without over stimulation. Over stimulation occurs when Estradiol levels get too high too quickly. This can have negative effects: although the egg numbers are often high, the egg quality may be decreased, the risk of hyper stimulation is increased (more about that later), and sometimes the lining of the uterus is adversely affected. Careful frequent monitoring is important not only to ensure good egg quality but also to help prevent complications of hyper stimulation.