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How Big Should Your Follicles be at Trigger?

Updated: Apr 19

Follicles that ranged from 12 to 19 mm on the morning of the trigger shot were more likely to produce mature oocytes (Abbara et al, 2018).


So, remember when I was talking about my IVF cycle being converted to an IUI? Well, someone, or multiple people, really made me lose my faith in our clinic's ability to assist us in our baby making process.

I actually had started this entry a while back, because when I had initially gone through my cycle monitoring, the nurse had said that they like for the follicles to be around 18 mm prior to the trigger. Ahhhh, if you're not in the TTC community, you probably don't know what the 'trigger shot' even is.

Ok, let's take a few steps back... If you can recall, in a natural cycle, the pituitary produces LH which causes luteinization of the follicles leading to ovulation of the oocyte or egg. In most human females, there is one egg released during each cycle, while the rest of the cohort in that cycle die off. LH is the natural trigger. Your trigger shot in your protocol may be a GnRH agonist - which causes the LH surge.

During IVF and IUI, you can do hyperstimulation or superovulation and produce more than one follicle large enough to ovulate an egg. The stimulation comes from the injections of FSH. In my particular protocol for IUI I was using gonal-f, but there are others. So, you have more FSH from your injections and this FSH binds to more follicles, which prevents atresia of these follicles (atresia is the process of death of the follicles). Your AFC or antral follicular count - the number of follicles on your day 3 assessment - will show you roughly how many follicles will grow to be a large enough size to ovulate or be available to collect for IVF. So, disappointingly, my AFC was 2. Once my doctor saw that my AFC went from 8 to 2, this was the start of the problems. I had a nurse whom was incredibly discouraging - I will call her the mean nurse. She was telling me to cancel the cycle altogether. I had already been waiting over 6 months to get started! I had to convince my doctor to let me go ahead with something. You just feel like you have wasted so much time! So, we converted from an IVF protocol to an IUI. I started out with 150IU gonal-f, and went in every 3 days for cycle monitoring which was an ultrasound and blood work.

Just so that we can compare, not that you should compare your protocol with mine, but everyone wants to know that they are not alone!

Cycle monitoring: As you can see, I had 2 follicles on the right and 0 on the left.

Fertility assessment
Nov 17
Cycle monitoring

After going in for an ultrasound on Nov 19th, the nurse mentioned that I had three follicles. So hey, 3 is better than 2, I guess!

After this, it was decided that I would take a smaller dose of the FSH to prepare for an IUI, instead of the heavy doses of FSH that were initially planned for my IVF cycle.

Gonal F

I started gonal-f. Hubby did well with doing the injections, and then I went in for cycle monitoring (CM), an ultrasound (U/S) and blood work.


It was good having an app to get an update, but I think it would have been really nice to actually speak to my doctor regarding my protocol. I really feel like they dropped the ball on my entire cycle.

So anyway, after a few days of stimulation, I started to get a lead follicle of 5 mm. It's good to get something measurable! I even had my case transferred to a nice nurse for a little bit!

Follicle sizes
Nov 23

So, I was told to continue with the FSH injections...

More meds

Three days later, my lead follicle was 8 mm. This is good! I thought, yea, the follicles are growing slowly, but they are still growing! Roughly 1mm per day - while in my readings the average was 1.3mm per day.

Follicle size
Nov 26

I was scheduled to go in on the following Sunday (three days later).

More monitoring

I expected to have at least one 11 mm follicles on that Sunday. But here is the report...

The mishap
Nov 29

I sit down with the nice nurse after my ultrasound report and I look at the sheet and see that my lead follicle is not measurable. What happened to my 8mm follicle that was supposed to be at least 11mm???? The nurse discusses with me, that it's not looking good. I don't have any follicles that are over 10 mm and that they want something around 18 mm before triggering for an IUI. My second devastation of this process.

The nurse says to me, we will likely have you come back on Tuesday or Wednesday. I am to take my gonal-f and wait for instructions on the app. I email my doctor's secretary asking if I can speak with my doctor. I'm wondering if I should cut my losses now and cancel this altogether.

I check my app on Sunday evening and receive a last minute booking for an ultrasound on Monday morning.

More monitoring

Geez!!! I have to scramble, I logged into my work system to see who was coming in for my appointments on Monday morning. I managed to send an email to one, and reschedule the other one. Talk about stressful!!!

I go in again on the Monday morning, another ultrasound and blood work.

Nov 30

I sit down with the nice nurse again (this is the nice nurse, not the mean one). She says, the reason we had you come in today was because your estrogen was really high. Over 600. It didn't make sense to have zero follicles above 10 mm and have estrogen this high! Ahhhh... So that ultrasound tech that worked the Sunday missed these follicles. The nurse says, things are much better, I feel relieved. I'm still going to continue with gonal-f and likely come in Tuesday or Wednesday at the latest.

I go to work, feeling a combination of disappointment from the missed ultrasound on Sunday and relief. Monday was its usual hectic schedule, and I had three missed calls - one from the secretary, one from the nurse and one no voice message - that turned out to be from the doctor. I check my app.

I look at it again... my IUI is cancelled and my app now read timed intercourse. What???

So, I leave a voice message for the nursing line, and the mean nurse happens to call back when I'm at my desk. She says my LH is high. I'm ovulating on my own and my IUI is now being converted to timed intercourse. That we have to do the deed tonight and tomorrow night. Then come back in 16 days for blood work.

My frustrations

I am now angry.

I am ovulating on my own because no one prescribed me an antagonist!!! WTF?! Why wasn't I on a antagonist? Why did the technician and nurse miss this? Why wasn't my doctor involved more?!? So many questions unanswered.

I already know I have a luteal phase defect, so I tell the nurse that I will need assistance with this, that it doesn't make sense to just do timed intercourse, since this is what my husband and I have been doing all along! So, I ask for some progesterone. She mentions that she will send the script to the office. I had an acupuncture session the next day, so I would pick it up them. The script wasn't there, but the gentlemen at the office gave me enough for two weeks - to get me to my beta test.

The male parties who are part of the TTC community know all about the struggles to perform when you're told you got to get it done now or never! Yes, that is the easy part fellas. No pressure right?!

So a few days afterwards, I start progesterone suppositories - 200 mg am and pm. I'm to take it until I have a negative beta test.

My hubby didn't have faith in our fertility clinic. As soon as the mean nurse told me to cancel, and my doctor gave up on our IVF cycle, he was done. He says, there is a reason that they are discouraging us. They just do not want to do IVF.

If you're on Facebook, you know there are several TTC groups on there. There are a lot of women who express their frustrations with clinics who do not know how to handle women with low AMH. That they refuse to do IVF with a small number of follicles. A clinic's success rate is dependent upon only taking cases that they know will have a higher chance of success. With low AMH, my success rate is already low.

What I didn't like is that they have this belief of empty follicles. All follicles have eggs at some point! It just means that the protocol chosen was incorrect for that individual, or the suction for follicular aspiration was incorrect. I know. Because we do histology on the ovaries in cattle and there are eggs in those follicles. I also know that there is a technique to trying to get the egg from each follicle. Sometimes you do not get all the eggs.

So, we gave up on that clinic, and moved across the country.

We arrived in BC on Dec 13th. I had to go to a walk-in clinic during the COVID-19 pandemic for my beta test.

My doctor's office called on Dec 17th to let me know that the beta test was negative.

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