Sorry for not being clear.
In an antagonist protocol, there are 2 types of meds during the stimulation phase. The first one is your regular stimulation med (or agonist) that contains FHS and sometimes LH to make your follicles grow. A problem with this is that all the follicles may not grow at the same rate and be ready for retrieval on the same day. That's why the second med (antagonist) will be introduced at some point to prevent any follicle from getting too much ahead of the others.
The question is when to start that antagonist to get the best results. One option that is the most common is to instruct patients to start it on a specific day of stimulation such as day 5 or day 6 (fixed start). Another option is to wait until the first ultrasound (those are done every 2 days or so starting on day 6 to monitor follicle growth) and then decide if the antagonist should be started that day or later (variable start).
What I was saying before is that there is some evidence that a variable start might give better results but many doctors forget to mention when to start the antagonist when they do the ultrasound. So, if you have a variable start date for the antagonist, you should be proactive and make sure to ask the doctor about it while you are in the ultrasound room.
Hope that makes a bit more sense.
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