• Eva

Stage 2: Trigger Shot

Why we need a Trigger Injection for oocyte maturation, and why it is so important to use it properly.


Let's learn the basics about the Trigger shot stage of the IVF treatment. Ovarian follicles are small fluid-filled sacs in the ovaries. Inside of each follicle is an immature egg, which grows and undergoes a set of changes. After the follicle reaches its optimal size, ovulation occurs and the mature egg is released.



After the Trigger Shot, I spent the next 36 hours before the egg retrieval relaxing and preparing myself for the egg collection.

During my ovarian stimulation period, I had two ultrasound appointments to check how my ovaries reacted to the hormone injections. I was quite surprised that a simple ultrasound test was able to detect my follicles. At the first appointment, we found four follicles, two on each ovary, and later on, one more little miracle follicle showed up on the screen. By the end of the stimulation stage, my ovaries developed five good looking follicles.


Five follicles is not a big number if we compare it to the optimal figure. Usually, anywhere between 8 and 15 follicles is considered an acceptable amount for an IVF treatment. Even though I received a fairly high dosage of fertility drugs, my ovaries reacted poorly to the stimulation. However, it only takes one egg to succeed, so the game has not been over yet!


The great news was that all of my follicles were a good size. When a follicle reaches the measurements between 16mm and 22mm, it is more likely that it contains a fully mature egg, which is ideal for the IVF process. All of my follicles reached this size, so it was definitely a small victory. The doctor also checked the thickness of my uterine lining, which was 12mm, and found it to be optimal for implantation.


The doctor gave us the green light to move forward to stage 2: the Trigger Shot, also called the Trigger Injection. The Trigger shot sends the eggs into meiosis (a state of reproductive division), and helps them to mature for egg collection. The objective is to decrease the number of chromosomes in the eggs from 46 to 23 prior to egg retrieval. If exactly 23 chromosomes are not present in the egg that undergoes fertilisation, it will not be able to create an embryo. I see now why it is so important.


The Trigger Shot usually contains the HCG hormone, which is the famous “pregnancy hormone” that we are looking for while taking a pregnancy test. After receiving the injection, ovulation can start between 36-48 hours. I had to use this single shot exactly 36 hours prior to my scheduled egg collection appointment. The most important step of the Trigger Shot is the timing; the success of the fertility treatment greatly depends on it and its effect on the quality of eggs. To make sure I did not forget this important task, I scheduled the shot in the Leeaf calendar, and waited for the selected time.


Injecting the Trigger Shot is exactly the same process as administering the daily hormonal stimulation shots, so there is nothing to be concerned about.